WO2025202270A1

WO2025202270A1 - Medical device for use as ureteral stent, biliary stent or urinary catheter in a human or animal body, medical system comprising such a device and method of acoustically activating such a device

Info

Publication number: WO2025202270A1
Application number: PCT/EP2025/058237
Authority: WO
Inventors: Francesco CLAVICA; Daniel AHMED; Cornelius Benjamin DILLINGER; Dominik OBRIST; Fiona Burkhard; Pedro PEREIRA AMADO
Original assignee: Eidgenoessische Technische Hochschule Zurich ETHZ; Universitaet Bern
Current assignee: Eidgenoessische Technische Hochschule Zurich ETHZ; Universitaet Bern
Priority date: 2024-03-28
Filing date: 2025-03-26
Publication date: 2025-10-02
Anticipated expiration: 2026-09-28

Abstract

The present invention relates to a medical device (100) for use as a ureteral stent, a biliary stent or a urinary catheter in a human or animal body. The medical device (100) comprises a hollow device body (101) having at least one body lumen (102), an inner body surface (105) and an outer body surface (106), wherein the inner body surface (105) delimits the at least one body lumen (102). The medical device (100) further comprises at least one array (110) of microstructures (111) located on the inner body surface (105) and/or the outer body surface (106) and configured to locally increase fluid-induced shear stress acting on the device body (101) in use of the medical device (100) in response to applying an acoustic field to the medical device (100). The invention further relates to a medical system comprising such as a medical device and an activation device configured to be positioned externally of a human or animal body, wherein the activation device comprises at least one sound transducer configured to generate an acoustic field for application from externally of the human or animal body to the medical device. The invention further relates to as to a method of acoustically activating such a medical device during use in a human or animal body, in particular for cleaning purposes and/or mass transport.

Description

DESCRI PTION

Title

MEDICAL DEVICE FOR USE AS URETERAL STENT, BILIARY STENT OR URINARY CATHETER IN A HUMAN OR ANIMAL BODY,

MEDICAL SYSTEM COMPRISING SUCH A DEVICE AND METHOD OF ACOUSTICALLY ACTIVATING SUCH A DEVICE

Technical Field

[0001 ] The present invention relates to a medical device for use as a ureteral stent, a biliary stent or a urinary catheter in a human or animal body comprising an array of microstructures configured to promote steady streaming in response to an acoustic field. The invention further relates to a medical system comprising such a medical device as well as to a method of acoustically activating such a medical device during use in a body of a subject, in particular for cleaning purposes and/or mass transport due to fluid flow.

[0002] Medical devices and systems employing such an array of microstructures can be used for providing a sound-activatable self-cleaning and/or mass transport mechanism.

Background Art

[0003] Medical stents and catheters are available for a large variety of medical applications in human or animal bodies, there serving as intraluminal prosthetic devices to repair, open, evacuate, replace, medicate or support a lumen in a human or animal recipient. The lumen may be part of a vascular system, a neurovascular system, a pulmonary tract, a urogenital tract, or a gastrointestinal tract in a human or animal body. The present invention specifically relates to medical stents and catheters for the urogenital tract and the gastrointestinal tract in human or animal bodies, more specifically to ureteral stents, biliary stents and urinary catheters for use in human or animal bodies. [0004] Ureteral stents, or ureteric stents, are thin tubes inserted into the ureter of a human or animal body to ensure the flow of urine from the kidney to the bladder for example in the case of an obstruction. Ureteral stents are available in various configurations and can be equipped with different features. Ureteral stents may comprise one or more side holes along their length to allow urine to pass through the stent. Ureteral stents may further comprise curled ends to locally stabilize the stent and prevent dislocation.

[0005] Urinary catheters are tubes for insertion into the bladder of a human or animal body suprapubically or through the urethra or to allow urine to drain from the bladder. Urinary catheters may also be used to inject liquids used for treatment or diagnosis of bladder conditions.

[0006] A biliary stent, also known as a bile duct stent, is a thin, hollow tube that is placed in the bile duct. The stent is configured to hold the bile duct open after the duct has been blocked or partly blocked.

[0007] A major complication with ureteral stents, biliary stents and urinary catheters is biofilm formation on the surfaces of the stents or catheters, respectively. Biofilms are complex communities of microorganisms attached to a surface, embedded in a selfproduced extracellular matrix (EPS). The EPS, secreted by the microorganisms, plays a crucial role on the resilience of biofilms by enhancing their protection against external threats, making them highly resistant to the most common antimicrobials and conventional cleaning methods. In healthcare, biofilm formation poses a significant threat, since it creates infections, negatively impacting both the patients' quality of life and healthcare resources. Crystal accumulation, also known as encrustation, poses another significant challenge, frequently resulting in obstruction of the catheter or stent, depending on the duration of placement and the composition of body fluids passing therethrough. Both, encrustations and biofilm formation can compromise the ability of the stents or catheters to effectively maintain liquid flow.

[0008] Surface encrustation and biofilm formation may occur on both the inner surfaces and the outer surfaces of stents or catheters, respectively. While internal surface encrustation and biofilm formation may cause internal obstruction reducing the drainage effectiveness, external surface encrustation and biofilm formation may also complicate stent or catheter removal. Encrustation and biofilm formation may also occur on the edges of side holes, reducing e.g. the ability of these catheters to maintain fluid drainage. Therefore, stents and catheters are replaced at regular intervals to avoid complications resulting from encrustation and biofilm formation. Consequently, patients may require frequent re-intervention, which on the one hand is often unpleasant for the patients and on the other hand consumes considerable financial and material resources.

[0009] Biofilm formation and encrustation on veterinary ureteral stents, biliary stents and urinary catheters can lead to similar complications as seen in human medicine, highlighting the universal impact of this problem across healthcare domains.

[0010] In recent years, progress has been made to reduce biofilm formation and encrustation on surfaces. Recent developments in biofilm research have improved outcomes using antimicrobial coatings, surface materials, topography changes, and activatable microstructures. While surface treatments, topography changes and microstructures may reduce or slow-down the initial stages of bacteria and crystal attachment, their long-term effectiveness remains uncertain. So far, other means also have not conclusively proven complete efficacy in the long-term removal of biofilm and encrustation or their prevention.

[0011 ] Therefore, there is a need for medical devices usable as ureteral stents, biliary stents or urinary catheters in a human or animal body which comprise improved means for preventing, reducing and/or removing biofilm formation and encrustation on the device surfaces.

Disclosure of the Invention

[0012] According to the invention this need is settled by a medical device as it is defined by the features of independent claim 1 , by a medical system as it is defined by independent claim 16, and by a method as it is defined by independent claim 24. Preferred embodiments are subject of the dependent claims.

[0013] In one aspect, the present invention relates to a medical device for use as a ureteral stent, a biliary stent or a urinary catheter in a human or animal body, in particular to treat ureteral or biliary obstructions in a human or animal body, for instance in cats, dogs, horses. [0014] As such, the medical device comprises a hollow device body having at least one body lumen, an inner body surface and an outer body surface, wherein the inner body surface delimits the at least one body lumen. The hollow device body may comprise a single body lumen or a plurality of body lumen. That is, the hollow device body may be a single-lumen device body or multi-lumen device body. The one or more body lumen may serve as drainage allowing liquid to pass therethrough, e.g. to allow urine to drain from the kidney or the bladder of a human or animal body.

[0015] The hollow device body may have two opposing ends, in particular two opposing open ends allowing liquid to enter and leave the at least one body lumen. More specifically, the hollow device body may have at least one inlet to the at least one body lumen and at least one outlet from the at least one body lumen. Preferably, the at least one inlet and the at least one outlet are arranged at opposing ends or opposing end portions of the hollow device body. The hollow device body may further comprise one or more side holes along its length allowing liquid to enter and leave the at least one body lumen.

[0016] The hollow device body may be an elongated hollow device body. In particular, the hollow device body may be a tubular device body. The hollow device body may further comprise one or two curled ends, in particular where the hollow device body is elongated or tubular.

[0017] Depending on the specific use of the medical device as ureteral stent, biliary stent or urinary catheter, the hollow device body, especially the elongated hollow device body or the tubular device body, may have an outer diameter or an equivalent outer diameter (as seen in a cross-section perpendicular to a length extension of the hollow device body) in a range between 0.5 mm and 15 mm, in particular between 2 Fr (French) and 30 Fr (between 0.66 mm and 9.9 mm), more particularly between 6 Fr and 30 Fr (between 2 mm and 9.9 mm), which may apply for urinary catheters used in human bodies, or between 4 Fr and 9 Fr (between 1.33 mm and 3 mm), which may apply for ureteral stents used in human bodies, or between 5 Fr and 12 Fr (between 1 .66 mm and 4 mm), which may apply for biliary stents used in human bodies, or for animal bodies between 0.5 mm and 15 mm for animal bodies, where 2.0 mm may apply e.g. for feline stents and 15 mm may apply e.g. for stents for horses. An inner diameter or an equivalent inner diameter of the hollow device body, especially the elongated hollow device body or the tubular device body, may be in similar ranges, yet reduced by two times a respective wall thickness of the device body. The wall thickness of the device body may be in a range between 0.2 mm and 3 mm, in particular between 0.5 mm and 2 mm, more particularly between 0.75 mm and 1 .5 mm. The term "equivalent diameter" is used herein in relation to a hollow device body of non-circular cross-sectional shape (e.g. an oval cross-sectional shape) and is defined as the diameter of a hollow device body with a circular cross-sectional shape which has the same cross-sectional surface area as the hollow device body of non-circular shape cross-sectional shape.

[0018] Depending on the specific use of the medical device as ureteral stent, biliary stent or urinary catheter and the specific application in a human or in an animal body, the hollow device body may be made of different materials and material compositions. The hollow device body can be flexible or semi-rigid or rigid. The hollow device body may comprise or may be made of a rigid material, such as a metal or glass or a rigid plastic, or a flexible material, such as polyurethane, rubber, latex, polyvinyl chloride (PVC), or silicone. The choice of material may especially determine the time the medical device may dwell in the human or animal body.

[0019] According to the invention, the medical device comprises at least one array of microstructures located on the inner body surface and/or the outer body surface, and/or - if present - on the edges of side holes. The at least one array of microstructures is configured to locally increase fluid-induced shear stress acting on the device body, more specifically on at least one or more portions of the inner body surface and/or the outer body surface, in use of the medical device when applying an acoustic field to the medical device. The at least one array of microstructures preferably is transparent to alternating magnetic fields.

[0020] As used to herein, the term "in use of the medical device" refers to a state, in which the medical device dwells at a dedicated place in a human or animal body, e.g. in the ureter, the urethra/bladder or the bile duct of a human or animal body, in which a fluid, such as urine or bile, is in contact with the least one array of microstructures, more specifically in which a fluid, such as urine or bile, is present inside the at least one body lumen and/or outside the hollow device body (extraluminal). For this, at least a portion of the inner body surface and/or a least a portion of the outer body surface, in particular those portions comprising an array of microstructures, may be liquid-wetted, i.e. wetted by a liquid, such as urine and bile. In use of the medical device, the at least one body lumen may be partially or entirely filled with a liquid, such as urine and bile. [0021 ] According to the invention it was found that providing an array of microstructures on the inner body surface and/or the outer body surface may be advantageous if it is configured such that in use of the medical device and upon applying an acoustic field thereto the array of microstructures locally modifies the fluid dynamics in proximity to the device body, more specifically in proximity to that portion(s) of the inner body surface and/or the outer body surface which comprise(s) the array of microstructures.

[0022] In this regard, it was found particularly advantageous if the array of microstructures is configured such that in use of the medical device and upon applying an acoustic field to the medical device the array of microstructures is capable to locally promote steady streaming in proximity to the device body, more specifically in proximity to that/those portion(s) of the inner body surface and/or the outer body surface and its/their surroundings which comprise(s) the array of microstructures. This may apply to both a continuous application of an acoustic field and an intermittent, in particular pulsed application of an acoustic field. In the latter case, a sequence of steady streaming can be achieved through a sequence of acoustic stimulations (e.g. pulsed acoustic stimulation).

[0023] The resulting flow pattern depends on various factors, including the frequency and intensity of the acoustic field, the shape, the size and the material of the microstructures, and the properties of the liquid.

[0024] The primary effect of the steady streaming promoted by the array of microstructures is a steady, non-oscillatory localized flow of liquid which comes along with enhanced fluid-induced shear stress. The latter can be advantageously used to dislodge attachments from a surface, more specifically from the inner body surface and/or the outer body surface, in particular from that/these portion(s) of the inner body surface and/or the outer body surface and its/their surroundings which comprises an array of microstructures according to the invention. In other words, the fluid-induced shear stress coming along with steady streaming promoted by the array of microstructures may be advantageously used as a cleaning mechanism to reduce or remove a contaminant, such as biofilms and/or encrustations, from the inner body surface and/or the outer body surface. Accordingly, the at least one array of microstructures may be configured to reduce or remove a contaminant, such as biofilms and/or encrustations, from the inner body surface and/or the outer body surface in response to applying an acoustic field to the medical device. As used herein, the term "contaminant" is used as generic term for biofilms and encrustations and other kind of deposits, accumulations, accretions, concretions on the device body". The description defines that in the present application "contaminant" is used as generic terms for biofilms and encrustations.

[0025] The steady streaming may involve the generation of steady, non-oscillatory, directional fluid flow in the liquid surrounding the medical device, in particular the array of microstructures, in use of the device. That is, the steady streaming promoted by the array of microstructures may supplement the bulk fluid velocity and thus may also increase the transport of detached contaminants away from the surface and into the bulk flow to prevent reattachment. In particular, the steady streaming may be used to actively transport fluid through the body lumen and/or along the outside of the device body. Accordingly, the at least one array of microstructures may be configured to generate a fluid flow, in particular a directional fluid flow, along the inner body surface and/or the outer body surface in response to applying an acoustic field to the medical device.

[0026] In particular, it was found that the microstructures may be capable - depending on their shape, size and material to promote a combination of acoustically induced vortexlike steady streaming and overall directional fluid flow pattern. In this regard, experiments have demonstrated that this kind of streaming is capable of detaching surface contaminants as clusters and trapping them within the vortex-like steady streaming. At this site, the acoustically induced streaming is capable of breaking up the trapped clusters of contaminants. Subsequently, debris resulting from these broken-up clusters may be flushed away by the directional fluid flow resulting from steady streaming.

[0027] In addition, it was found that the microstructures according to the present invention may enable an effective cleaning even in regions of stagnant flow, also known as dead cavity zones. In medical stents and catheters, such dead cavity zones may be typically formed when intraluminal obstructions, e.g. stones or strictures, or extraluminal obstructions, e.g. due to tumors or pregnancy, impede fluid flow, creating stagnant zones, especially near side holes of the stent or catheter. Such regions of stagnant flow are particularly prone to encrustations and biofilm formation. Experiments have demonstrated that such dead zones - if equipped with microstructures according to the present invention - can be effectively cleaned by the above-described steady streaming that is promoted by the microstructures. In this regard, it was found that the steady streaming can lead to the generation of significant bulk flow in stagnant flow regions. [0028] As described, the array of microstructures according to the present invention may locally increase fluid-induced shear stress acting on the device body when exposed to an acoustic field. In particular, it was found that the fluid-induced shear stress can be significantly increased as compared to an inner body surface and/or outer body surface comprising no such array of microstructures, in particular as compared to a smooth inner body surface and/or body outer portion. More specifically, the at least one array of microstructures may be configured - when exposed to an acoustic field in use of the medical device - to generate locally increased fluid-induced shear stress onto the device body of at least 0.001 Pa, in particular of at least 0.01 Pa, more particularly of at least 0.1 Pa or of at least 1 .0 Pa or of at least 10 Pa or of at least 100 Pa or of at least 500 Pa. Likewise, the at least one array of microstructures may be configured - when exposed to an acoustic field in use of the medical device - to generate locally increased fluid-induced shear stress onto the device body in a range between 0.001 Pa and 500 Pa or between 0.01 Pa and 500 Pa, in particular between 1 Pa and 500 Pa or between 1 Pa and 100 Pa or between 1 Pa and 10 Pa . As used herein, the term "increased shear stress" refers to shear stress on a surface of a device body comprising microstructures according to the invention that is increased as compared to a shear stress on a surface of a device body comprising no such microstructures, in particular as compared to shear stress onto a smooth surface.

[0029] In addition to the above-described sound-activatable self-cleaning and/or mass transportation mechanisms, the application of an acoustic field may also induce cavitation, resulting in the generation of bubbles and associated streaming in the fluid. This process may further contribute to the cleaning of the medical device.

[0030] As used herein, the term "microstructures" refers to structures at scales in the sub-millimeter range, more specifically at scales smaller than 1 millimeter, in particular smaller than 500 micrometers, more specifically smaller than 250 micrometers, but preferably at scales above 1 micrometer. Elements, shapes and distances (spacing) between elements forming the structure(s) may have dimensions in a range between 1 micrometer and 800 micrometers between 1 micrometer and 500 micrometers, in particular between 1 micrometer and 250 micrometer or between 5 micrometer and 250 micrometers, more particularly between 10 micrometer and 250 micrometer or between 10 micrometer and 200 micrometers. In particular, the term "microstructures" as used herein may refer to structures having dimensions, especially a height, a depth, a diameter, a width, and/or a length, which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a crosssection perpendicular to a length extension of the hollow device body).

[0031 ] Furthermore, as used herein, the term "microstructures" may especially refer to artificial microstructures or synthetic microstructures, i.e. to microstructures intentionally created or produced, in particular by some kind of processing, such as laser cutting or 3D printing or milling or extrusion by a specifically designed nozzle structure.

[0032] The term "array of microstructures located on the inner body surface and/or the outer body surface" may include that the array of microstructures is part of the inner body surface and/or the outer body surface, i.e. part of the device body, in particular integral part of the device body and thus forms (a least a portion) of the inner body surface and/or the outer body surface. Likewise, the term "array of microstructures located on the inner body surface and/or the outer body surface" may also include that the array of microstructures itself is separate from the device body, i.e. not (integral) part of the device body, but arranged on the inner body surface and/or the outer body surface, nevertheless thus still forming (a least a portion) of the inner body surface and/or the outer body surface. In general, the medical device may comprise one or more arrays of microstructures on the inner body surface and/or one or more arrays of microstructures on the outer body surface. In particular, the medical device may comprise an array of microstructures extending across substantially the entire inner body surface and/or an array of microstructures extending across substantially the entire outer body surface. Alternatively, the medical device may comprise one or more arrays of microstructures covering or forming only a part of the inner body surface and/or one or more arrays of microstructures covering or forming only a part of the outer body surface. In particular, the medical device may comprise a plurality of (separate) arrays of microstructures on the inner body surface and/or a plurality of (separate) arrays of microstructures on the outer body surface. Combinations of the afore-mentioned configurations are also possible. For example, the medical device may comprise one or more arrays of microstructures only on the inner body surface or one or more arrays of microstructures on the outer body surface only. Likewise, the medical device may comprise an array of microstructures extending across substantially the entire inner body surface or across substantially the entire outer body surface, whereas on the respective other body surface the medical device comprises no array of microstructures or a plurality of (separate) arrays of microstructures. In addition, the medical device may comprise an array of microstructures at the edges of sides holes, if present.

[0033] The at least one array of microstructures may be provided as a support element, e.g. a patch or a carpet, comprising, in particular carrying, the array of microstructures. In particular, the support element comprising the array of microstructures can have a flat shape, e.g. a flat rectangular shape, or a strip-like or band-like shape. In the medical device, the support element comprising the array of microstructures may be arranged on the in the inner body surface and/or the outer body surface. In particular, where the support element has a strip-like or band-like shape, the support element may be flexible allowing it to be wound up in a helical configuration such that the at least one array of microstructures may be either on the outside or the inside of the helical configuration. With the at least one array of microstructures on the outside, the helical configuration may be arranged on the outer body surface of the hollow device body of the medical device such that the at least one array of microstructures points outwards. The inner diameter of the helical configuration preferably is chosen such that it matches the outer diameter of the hollow device body. In particular, it is possible that the band- or strip-like support member is wound up in a helical configuration around the outer circumference of the hollow device body and/or on the inner circumference of the hollow device body such that the helical configuration is arranged on the inner and/or the outer body surface of the hollow device body of the medical device.

[0034] The at least one array of microstructures may comprise an array of microprotrusions, i.e. an array of elements protruding above a base level of the inner body surface and/or a base level of the outer body surface, in particular above a base level of an adjacent portion of the inner body surface and/or of the outer body surface having no microstructures.

[0035] The at least one array of microstructures may comprise sharp-edged microstructures, especially soft (non-rigid) sharp-edged microstructures.

[0036] In particular, the at least one array of microstructures or the array of microprotrusions, respectively, may comprise an array of micro-lamellae or an array of microcilia or an array of micro-pillars or an array of micro-sheds. [0037] The micro-protrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have a respective tapered free end portion. Such tapered free end portions may facilitate oscillations of the free end portions in response to applying an acoustic field to the medical device. Such oscillations may beneficially modify the fluid dynamics in proximity to the device body such that the reduction or removal of contaminants from the inner body surface and/or the outer body surface may further be enhanced. However, even where the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds are rather rigid and thus may possibly be not subject to oscillations, the cleaning and/or mass transport mechanism may nevertheless be present, e.g. due to boundary layer streaming.

[0038] Likewise, the at least one array of microstructures may comprise an array of micro-recesses, i.e. an array of elements or shapes recessed (set back) from a base level of the inner body surface and/or a base level of the outer body surface, in particular from a base level of an adjacent portion of the inner body surface and/or of the outer body surface having no microstructures.

[0039] In particular, the at least one array of microstructures may comprise an array of micro-grooves or an array of micro-dimples.

[0040] As defined above, the least one array of microstructures involves structures at scales in the sub-millimeter range. This may refer to one of: a height, a depth, a diameter, a width, a length or an inter-array distance (spacing, in particular a periodicity) of or between elements and/or shapes forming the microstructures. Accordingly, elements and/or shapes forming the least one array of microstructures may have one of a height, a depth, a diameter, a width, a length or an inter-array distance (spacing, in particular a periodicity) in a range between 1 micrometer and 500 micrometers, in particular between 1 micrometer and 250 micrometer or between 5 micrometer and 250 micrometers, more particularly between 10 micrometer and 250 micrometer or between 10 micrometer and 200 micrometers. In particular, elements and/or shapes forming the least one array of microstructures may have one of a height, a depth, a diameter, a width, a length or an inter-array distance (spacing, in particular a periodicity), which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a cross-section perpendicular to a length extension of the hollow device body). [0041 ] The micro-recesses, in particular the micro-grooves or micro-dimples, may have a depth in a range between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 75 micrometers, for example 20 micrometer or 100 micrometer or 175 micrometers. Likewise, the microprotrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have a height or a length in a range between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 75 micrometers, for example 20 micrometer or 100 micrometer or 175 micrometers. Preferably, the micro-protrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have a height or a length, which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably 20, more preferably 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a cross-section perpendicular to a length extension of the hollow device body). Likewise, the micro-recesses, in particular the micro-grooves or microdimples, may have a depth which is smaller by at least one order of magnitude (i.e. by at least a factor of 10) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a cross-section perpendicular to a length extension of the hollow device body). In this regard, it has been found that the height or length of micro-structures formed as micro-protrusions may influence the type of fluid flow generated in use of the device.

[0042] The micro-recesses, in particular the micro-grooves or micro-dimples, may have an inter-recess distance (inter-groove distance or inter-dimple distance) in a range between 1 micrometer and 400 micrometer or between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, for example 50 micrometer or 80 micrometer or 100 micrometers. Preferably, micro-recesses, in particular the microgrooves or micro-dimples, may have an inter-recess distance (inter-groove distance or inter-dimple distance) which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a crosssection perpendicular to a length extension of the hollow device body). Likewise, the micro-protrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have an inter-protrusion distance/spacing (inter-lamella distance/spacing or inter-cilia distance/spacing or inter-pillar distance/spacing or intershed distance/spacing) in a range between 1 micrometer and 400 micrometer or between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, for example 50 micrometer or 80 micrometer or 100 micrometers. In particular, the microprotrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have an inter-protrusion distance/spacing (inter-lamella distance/spacing or inter-cilia distance/spacing or inter-pillar distance/spacing or intershed distance/spacing) which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a crosssection perpendicular to a length extension of the hollow device body).

[0043] The micro-recesses, in particular the micro-grooves or micro-dimples, may have a width or a diameter/an equivalent diameter (in particular as measured at a base level of the inner body surface and/or a base level of the outer body surface) in a range between 1 micrometer and 200 micrometers or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 50 micrometers, for example 20 micrometer or 30 micrometer or 40 micrometers. Preferably, the micro-recesses, in particular the micro-grooves or micro-dimples, may have a width or a diameter/an equivalent diameter (in particular as measured at a base level of the inner body surface and/or a base level of the outer body surface) which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a cross-section perpendicular to a length extension of the hollow device body). Likewise, the micro-protrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have a width or a diameter/an equivalent diameter (in particular as measured at a base level of the inner body surface and/or a base level of the outer body surface) in a range between 1 micrometer and 200 micrometers or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 50 micrometers, for example 20 micrometer or 30 micrometer or 40 micrometers. Preferably, the micro-protrusions, in particular the micro-lamellae or the micro-cilia or the micro-pillars or the micro-sheds, may have a width or a diameter/an equivalent diameter (in particular as measured at a base level of the inner body surface and/or a base level of the outer body surface) which is smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a cross-section perpendicular to a length extension of the hollow device body). [0044] Preferably, the array of microstructures has a periodic microstructure pattern in at least one direction, in particular in one or two directions. That is, the microstructures are of the same dimensions and are spaced from each other by the same distance in at least one direction, in particular in one or two directions. A periodicity of the array of microstructures in at least one direction, in particular in one or two directions, may be in range between 1 micrometer and 400 micrometer or between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, for example 70 micrometer or 110 micrometer or 140 micrometers. Preferably, a periodicity of the array of microstructures in at least one direction, in particular in one or two directions, may be smaller by at least one order of magnitude (i.e. by at least a factor of 10, preferably a factor of 20, more preferably a factor of 30) than an outer diameter or an equivalent outer diameter of the hollow device body (as seen in a cross-section perpendicular to a length extension of the hollow device body).

[0045] The optimum values and/or ranges for the dimensions of the aforementioned parameters may depend - inter alia - on the frequency of the acoustic field applied to the medical device in use. Or vice versa, the frequency of the acoustic field to be applied to the medical device may preferably be chosen such that it matches with the dimensions of the microstructures.

[0046] As described above, the steady streaming promoted by the array of microstructures may supplement the bulk fluid velocity in use of the device. That is, the at least one array of microstructures may be configured to generate a fluid flow, in particular a directed, non-oscillatory fluid flow, along the inner body surface and/or the outer body surface in use of the medical device in response to applying an acoustic field to the medical device.

[0047] The fluid flow may be promoted if the array of microstructures comprises microstructures which are angled relative to the inner body surface and/or the outer body surface, more specifically relative to a base level of the inner body surface and/or a base level of the outer body surface. Here, the direction of the inclination relative to (the base level of) the inner body surface and/or to (the base level of) the outer body surface defines a general direction of the fluid flow generated by the array of angled microstructures. Accordingly, the at least one array of microstructures may comprise microstructures angled relative to the inner body surface and/or the outer body surface, more specifically relative to a base level of the inner body surface and/or a base level of the outer body surface, by an angle greater than 0° and less than or equal to 90°, especially greater than 0° and less than 90°, in particular in a range between 20° and 80°, in particular 45° and 70°, for example by 65°. These values may refer to any orientation of the microstructures, e.g. an orientation along a main direction of fluid low through or along the device body, an orientation opposite to a main direction of fluid low through or along the device body, or an orientation transvers to a main direction of fluid low through or along the device body. So, in general, the angle may be in a range between 0° to 90° and from 90° to 180°. Advantageously, such inclined microstructures may also be used to clean dead cavity zones since inclined microstructures have proven beneficial to generate significant bulk flow in stagnant flow regions.

[0048] It is also possible that the at least one array of microstructures comprises microstructures angled relative to each other. That is, the at least one array of microstructures may comprise microstructures angled relative to the inner body surface and/or the outer body surface, more specifically relative to a base level of the inner body surface and/or a base level of the outer body surface, by different angles. In particular, the at least one array of microstructures may comprise adjacent microstructures angled relative to each other such that adjacent microstructures are essentially directed towards each other. It is also possible that the at least one array of microstructures may comprise adjacent microstructures angled relative to each other such that adjacent microstructures are facing in opposite directions. Having microstructures angled relative to each other may help to promote vortical fluid flow which in turn may also enhance the reduction or removal of contaminants from the inner body surface and/or the outer body surface.

[0049] Depending on the specific use of the medical device as ureteral stent, biliary stent or urinary catheter, the device body may comprise at least one aperture extending from the outer surface through the device body into the at least one body lumen. For example, the aperture may be a drainage opening (also known as drainage eye) or a side hole of the device body, such as a drainage eye or a side hole of a ureteral stent or a urinary catheter.

[0050] Preferably, the at least one array of microstructures comprises microstructures which are located adjacent to the at least one aperture. In this regard, it was found that microstructures located adjacent to such an aperture may beneficially modify the fluid dynamics in proximity to the aperture which in turn may cause a reduction or removal of contaminants, or may even prevent the formation of contaminants in proximity to the aperture.

[0051 ] Advantageously, a density of the microstructures located adjacent to the at least one aperture may vary as a function of distance from the at least one aperture. In this regard, it has been proven particularly advantageous in terms of cleaning efficacy, if the density of microstructures located adjacent to the at least one aperture decreases with increasing distance from the at least one aperture. It is also possible that the density of microstructures located adjacent to the at least one aperture increases with increasing distance from the at least one aperture.

[0052] According to the invention, the cleaning (and transport) mechanism is activated, in particular exclusively activated, by an acoustic field applied to the medical device in use. That is, the cleaning (and transport) mechanism provided by the array of microstructures is (purely) acoustically driven or actuated, preferably by ultrasound. Acoustic activation, in particular sound activation, more particularly ultrasound activation offers several advantages over other activation mechanisms, such as magnetic activation. Among others, the key benefit is the low-cost and simplicity of fabrication since sound, in particular ultrasound only requires a simple sound transducer, such as a piezo transducer. In addition, as compared with magnetically activated microstructures, the achievable frequencies with sound, in particular ultrasound activation can be much higher, such as in the range of some hundred Hz up to some hundred some hundred kHz or even higher up to hundred MHz, thus offering higher potential in reaching efficient cleaning due to higher velocity streaming resulting in larger shear stress exerted onto the device surface.

[0053] Preferably, the at least one array of microstructures according to the present invention is transparent to alternating magnetic fields. Transparency to alternating magnetic fields may be accomplished if the microstructures are made of a non-magnetic material. As used herein, the term "non-magnetic material" refers to materials which do not exhibit strong magnetic response, more specifically which have a low relative magnetic permeability very close to unity, in particular a relative magnetic permeability below 10, more particularly below 5 or below 2. Thus, if an alternating magnetic field is applied to the magnetically transparent microstructures, they will show no kinematic response, in particular they will not move, vibrate or oscillate in response to the alternating magnetic field. [0054] Preferably, the medical device is free of any active driving mechanism for setting the microstructures in motion. That is, the at least one array of microstructures preferably is an array of passive microstructures.

[0055] Furthermore, the at least one array of microstructures preferably is free of any electro-strictive materials, piezoelectric materials or magneto-strictive materials, and/or shape-memory materials.

[0056] If at all, the microstructures may be configured to move, in particular oscillate or vibrate, in response to (especially exclusively in response to) an acoustic field applied to the medical device in use. Such movement may be either directly induced (excited) by the applied acoustic field or (only) fluid-induced by the fluid dynamics described above occurring in use of the medical device. It is also possible that such movement is due to both, direct excitation by the applied acoustic field and fluid-induced by the fluid dynamics. Whether the microstructures are configured to move may also depend on the material properties (such as stiffness), and the geometry (shape and dimensions) of the microstructures.

[0057] In general, the microstructures may be rigid microstructures or flexible microstructures. This may especially apply to microstructures comprising microprotrusions, such as micro-lamellae or micro-cilia or micro-pillars or micro-sheds. Accordingly, the at least one array of microstructures comprises an array of rigid and/or flexible micro-protrusions, in particular an array of rigid and/or flexible micro-lamellae or an array of rigid and/or flexible micro-cilia or an array of rigid and/or flexible micro-pillars or an array of rigid and/or flexible micro-sheds. Where the microstructures are flexible microstructures, the acoustic field applied to the medical device may especially induce a movement of the flexible microstructures which in turn may generate a steady streaming as described above. Likewise, where the microstructures are rigid microstructures, the acoustic field applied to the medical device may especially impact against the rigid microstructures, thereby generating a steady streaming as described above. It is also possible. A combination of the two phenomena (acoustic field induces movement - acoustic field impacts against microstructures) described before is also possible.

[0058] The invention further relates to a medical system comprising a medical device of the invention and as above described, as well as an activation device configured to be positioned externally of a body of a subject, wherein the activation device comprises at least one sound transducer configured to generate an acoustic field for application to the medical device from externally of the body of the subject. The body of the subject may be a human body or an animal body, such as a body of a cat, a dog or a horse.

[0059] The sound transducer may be configured to generate an acoustic field with a frequency in a range between 1 Hz and 100 MHz, in particular between 1 kHz and 1 MHz, especially in range between 10kHz and 200kHz, or between 10kHz and 100kHz or between 20kHz and 100kHz; or above 20kHz or in the ultrasound range. Preferably, the sound transducer is capable of generating an acoustic field at different frequencies, i.e. with a variable frequency.

[0060] The activation device may comprise one (a single) sound transducer or a plurality of sound transducers. In particular, the activation device may comprise an array of sound transducers, i.e. a sound transducer array.

[0061 ] Preferably, the at least one sound transducer is or comprises a piezo transducer.

[0062] The amplitude of the streaming, in particular the steady streaming used at hand to reduce or remove a contaminant from the inner body surface and/or the outer body surface is a function of the frequency and the intensity of the acoustic field applied to the medical device. Accordingly, the sound transducer may be configured to generate an acoustic field at different frequencies and/or at different intensities.

[0063] Furthermore, the sound transducer may be configured to generate an acoustic field in a continuous mode and/or in a pulsed mode. That is, the sound transducer may be configured to generate an acoustic field continuously, for example, over a predetermined activation period. Alternatively, the sound transducer may be configured to generate an acoustic field intermittently, in particular in one or more pulses, such as trains of acoustic field pulses. For example, the sound transducer may be configured to generate an acoustic field such that the acoustic field is repeatedly on for 0.8 seconds, and off for 0.2 seconds. Where the acoustic field is applied as pulses, in particular as pulse train, the intensity, the sound transducer may be configured to vary the intensity, the frequency and/or the direction of the acoustic field from pulse to pulse. For example, the sound transducer may be configured to increase the intensity of the acoustic field from pulse to pulse. [0064] The device may further comprise a power-control unit for powering and controlling the sound transducer. The power-control unit may in particular configured to the frequency and/or the intensity of the acoustic field generated by the sound transducer.

[0065] The power-control unit may be further configured to control a directionality of the acoustic field transmitted by the sound transducer. Advantageously, this may facilitate to address specific regions within the human or animal body.

[0066] The activation device may also comprise a retaining structure configured to press the sound transducer into abutment with the human or animal body. Such a retaining structure may help to increase the transmission efficiency of the acoustic field to the human or animal body.

[0067] In particular, the activation device may comprise a wearable device which comprises the retaining structure. Advantageously, the medical system may thus be used in as portable device, which the patient (human being or animal) may carry with h i m/her/it. This is of particular interest, if the array of microstructures is to be used not only on specific occasion, e.g. occasional cleaning procedure, but more or less continuously, e.g. once or even several times throughout the day, or several times per week, e.g. for actively maintaining or supporting a fluid flow through the medical device.

[0068] The present invention further relates to a method of acoustically activating a medical device according to the present invention during use in a body of a subject, in particular for cleaning purposes and/or mass transport, the method comprising applying an acoustic field to the medical device from externally of the body of the subject. The body of the subject may be a human body or an animal body, such as a body of a cat, a dog or a horse.

[0069] The acoustic field may have a frequency in a range between 1 Hz and 100 MHz, in particular between 1 kHz and 1 MHz, especially in range between 10kHz and 200kHz, or between 10kHz and 100kHz or between 20kHz and 100kHz; or above 20kHz or in the ultrasound range.

[0070] Applying an acoustic field to the medical device may comprise applying an acoustic field to the medical device at different frequencies and/or at different intensities and/or from different directions (at different times). [0071 ] Furthermore, applying an acoustic field to the medical device may comprise applying an acoustic field to the medical device continuously, for example, over a predetermined activation period. Alternatively, applying an acoustic field to the medical device may comprise applying an acoustic field to the medical device intermittently, in particular in one or more pulses, such as trains of acoustic field pulses. For example, the acoustic field may be repeatedly on for 0.8 seconds, and off for 0.2 seconds. Where the acoustic field is applied as pulses, in particular as pulse train, the intensity, the frequency and/or the direction of the acoustic field may vary from pulse to pulse. For example, the intensity of the acoustic field may increase from pulse to pulse.

Brief Description of the Drawings

[0072] The medical device and the medical system according to the invention are described in more detail hereinbelow by way of an exemplary embodiment and with reference to the attached drawings, in which:

Figs. 1 a-1 c schematically show an exemplary embodiment of a medical system according to the present invention;

Fig. 2 shows details of a medical device according to a first embodiment of the present invention;

Fig. 3 shows details of a medical device according to a second embodiment of the present invention;

Fig. 4 shows details of a medical device according to a third embodiment of the present invention;

Fig. 5 shows details of a medical device according to a fourth embodiment of the present invention;

Fig. 6 shows details of a medical device according to a fifth embodiment of the present invention;

Fig. 7 shows details of a medical device according to a sixth embodiment of the present invention;

Figs. 8-10 show experimental results with a test-setup mimicking a medical system according to the present invention; and

Fig. 11 shows details of a medical device according to a seventh embodiment of the present invention. of Embodiments

[0073] In the following description certain terms are used for reasons of convenience and are not intended to limit the invention. The terms “right”, “left”, “up”, “down”, “under" and “above" refer to directions in the figures. The terminology comprises the explicitly mentioned terms as well as their derivations and terms with a similar meaning. Also, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", "proximal", "distal", and the like, may be used to describe one element's or feature's relationship to another element or feature as illustrated in the figures. These spatially relative terms are intended to encompass different positions and orientations of the devices in use or operation in addition to the position and orientation shown in the figures. For example, if a device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be "above" or "over" the other elements or features. Thus, the exemplary term "below" can encompass both positions and orientations of above and below. The devices may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly. Likewise, descriptions of movement along and around various axes include various special device positions and orientations.

[0074] To avoid repetition in the figures and the descriptions of the various aspects and illustrative embodiments, it should be understood that many features are common to many aspects and embodiments. Omission of an aspect from a description or figure does not imply that the aspect is missing from embodiments that incorporate that aspect. Instead, the aspect may have been omitted for clarity and to avoid prolix description. In this context, the following applies to the rest of this description: If, in order to clarify the drawings, a figure contains reference signs, which are not explained in the directly associated part of the description, then it is referred to previous or following description sections. Further, for reason of lucidity, if in a drawing not all features of a part are provided with reference signs it is referred to other drawings showing the same part. Like numbers in two or more figures represent the same or similar elements.

[0075] Fig. 1 a schematically illustrates an exemplary embodiment of a medical system 10 according to the present invention which at hand includes two medical devices 100 according to the invention especially conceived as ureteral stents for use in a human body l . Accordingly, the medical devices 100 shown in Fig. 1 a may be denoted as ureteral stents configured for use in a human body 1 . As such, each of the medical devices 100 (ureteral stents) according to the present embodiment comprises a tubular hollow device body 101 for insertion into one of the ureters 2 of a human body 1 in order to prevent or treat obstruction of urine flow from the kidneys 3 to the bladder 4, i.e. to ensure the openness of the ureters 2. Each hollow device body 101 has two opposing ends, whereby after insertion of the device body 101 into the respective ureter 2, one end

103 comes to rest in the collecting system (renal pelvis) of the kidney 3 and the other end

104 in the bladder 4. In addition, each of the hollow device bodies 101 comprises several side holes 107 (see Fig. 2, not shown in Fig. 1 ) along their length to bypass ureteral obstructions.

[0076] Fig. 1 b schematically illustrates another exemplary embodiment of a medical system 10 according to the present invention which comprises a medical device 100 according to the invention that is especially conceived as biliary stent. At hand, the biliary stent, also known as a bile duct stent, is configured for use in a human body 1 , only a part of which is illustrated in Fig. 1 b depicting the liver 11 , the bile duct 12, the gallbladder 13, the duodenum 14, the pancreas 15 and the pancreatic duct 16. The biliary stent comprises a thin, tubular hollow device body 101 that is placed in the bile duct 12 and configured to hold the bile duct 12 open after the duct has been blocked or partly blocked.

[0077] Fig. 1 c schematically illustrates another exemplary embodiment of a medical system 10 according to the present invention which comprises a medical device 100 according to the invention that is especially conceived as urinary catheter for use in a human body 1 . As shown, the urinary catheter comprises a tubular hollow device body 101 for insertion into the bladder 24 through the urethra 23 to allow urine to drain from the bladder 24.

[0078] Like many medical devices in contact with the urinary or bile tract of a human or animal body, ureteral stents, biliary stents and urinary catheters are subject to contaminants from the urinary or biliary tract environment, in particular biofilm formation and encrustations. These contaminants can occur on the luminal inner surface of the ureteral stents, biliary stents and urinary catheters, even to the extent of occluding them, as well as on the outer surface, creating pain and complications, such as the inability of remove the stents.

[0079] To remedy these problems, the present invention suggests to equip medical devices usable as ureteral stents, biliary stents or urinary catheters in a human or animal body with an array of microstructures which is configured to reduce or remove a contaminant from the surfaces of the medical device upon applying an acoustic field, in particular an ultrasonic field. Details and different embodiments of the microstructures are now described with reference to Fig. 2 to Fig. 6.

[0080] Fig. 2 shows details of a first embodiment of the medical device 100, which can be used, for example, as ureteral stent, biliary stent or urinary catheter in a human body 1 as shown and described before with reference to Figs. 1 a-1 c. As illustrated in Fig. 2, the medical device 100 comprises a tubular-shaped hollow device body 101 having a body lumen 102, an inner body surface 105 and an outer body surface 106, wherein the inner body surface 105 delimits the body lumen 102. In addition, the device body 101 comprises several apertures 107 (side holes) along its length, extending from the outer body surface 106 through the device body 101 into the body lumen 102. The apertures 107 may serve as drainage openings, for instance, to bypass ureteral obstructions.

[0081 ] According to the invention, it has been found that an efficient cleaning mechanism for reducing or even removing the above-described surfaces contaminants may be achieved by providing an array 110 of microstructures 111 on the inner body surface 105 and/or the outer body surface 106 which is configured such that in response to applying an acoustic field to the device body 101 the array 110 of microstructures 111 locally modifies the fluid dynamics in proximity to the device body 101 , namely, such that the formation of steady streaming in proximity to the device body 101 is promoted which in turn results in increased fluid-induced shear stress on the device body 101 that is capable to dislodge the surfaces contaminants. In this regard, the term "fluid dynamics in proximity to the device body 101" refers to the fluid dynamics of liquid that is present inside the body lumen 102 and/or around the device body 101 in use of the device, more specifically in proximity to that portion(s) of the inner body surface 105 and/or the outer body surface 105 comprising microstructures. With reference to the specific example of a ureteral stent as shown in Fig.1 , the liquid within the body lumen 102 and/or around the device body 101 is urine that is passing through the body lumen 102 of the device body 101 and/or around the device body 101 of the ureteral stent within the ureter 2.

[0082] As shown in Fig. 2, which only depicts a section of the medical device 100, the medical device 100 according to the first embodiment comprises microstructures 111 only on the inner body surface 105, while the outer body surface 106 is substantially smooth. At hand, the array 110 of microstructures 111 is an array of micro-protrusions 112 which extends across substantially the entire inner surface 105 - apart from those axial surface portions 105' of the device body 101 comprising apertures 107. More specifically, as can be best seen in the enlarged window of Fig. 2, the micro-protrusions 112 are micro-cilia 113 which protrude above a base level 108 of the inner body surface 105 substantially radially inwards into the body lumen 102. The array 110 of microstructures 111 , i.e. the micro-cilia 113 are integral with the device body 101 and thus form part of the inner body surface 105. As can be further seen from Fig. 2, each of the micro-cilia 113 has a tapered free end portion 114, causing the cilia to have a shape resembling a pointed pike.

[0083] The micro-cilia 113 may have a height or length in range in a range between 1 micrometer and 200 micrometers, and a width as measured at the base level 108 of the inner body surface 105 in a range between 1 micrometer and 100 micrometers. In the specific example at hand, the micro-cilia 113 have a height or length of 100 micrometer and a width of 30 micrometer as measured at the base level 108 of the inner body surface 105. The inter-cilia distance (spacing) between adjacent micro-cilia 113 may be in range between 1 micrometer and 200 micrometers. At hand, the inter-cilia distance (spacing) between adjacent micro-cilia 113 is 80 micrometers. Advantageously, these dimensions have proven to promote both, dipole-like fluid flow patterns with vortices around the cilia tips as well as "tip-to-tip" motion, generating significant fluid flow and high shear forces.

[0084] The micro-cilia 113 as well as the entire device body 101 are made of a polymer material, which is non-magnetic such that the micro-cilia 113 as well as the entire device body 101 are transparent to alternating magnetic fields. As a result, the micro-cilia 113 show no kinematic response, if an alternating magnetic field was applied. Rather, the micro-cilia 113 represent an array of passive microstructures which is free of any active driving mechanism for setting the microstructures in motion.

[0085] According to the invention, cleaning is only achieved by applying an acoustic field to the medical device 100, i.e. cleaning is only activated by sound. For this, the medical system 10 comprises an activation device 90 which is configured to be positioned externally of the human body 1 as schematically illustrated in Figs. 1 a-1 c. The activation device 90 comprises a sound transducer 91 that is configured to generate an acoustic field 93 which in use is applied from externally of the body 1 to the medical device inside the human body 1. At hand, the sound transducer is a piezo transducer. In addition, the activation device 90 comprises a power-control unit 92 for powering and controlling the sound transducer 91 . [0086] The amplitude of the steady streaming used at hand to reduce or remove surface contaminant from the device body 101 is a function of the frequency and the intensity of the acoustic field applied to the medical device 100. In general, the sound transducer 91 may be configured to generate an acoustic field with a frequency in a range between 1 Hz and 100 MHz. Preferably, the sound transducer 91 is capable of generating an acoustic field at different frequencies and/or at different intensities, i.e. with variable frequency and variable intensity. At hand, the sound transducer 91 is configured to generate an acoustic field at different frequencies in a range between 1 kHz and 200 kHz, i.e. at frequencies in both the audible range and the ultrasound range.

[0087] Fig. 3 shows a second embodiment of the medical device 200 according to the invention. In principle, the medical device 200 of Fig. 3 is similar to the medical device 100 of Fig. 2. Therefore, similar or identical features are denoted by the same reference numbers, yet incremented by one hundred. In contrast to the medical device 100 of Fig. 2, the medical device 200 of Fig. 3 does not comprise a substantially continuous array of microstructures, but a plurality of separate arrays 210 of microstructures 211 (provided as patches or carpets of microstructures 211 ) on both the inner body surface 205 and the outer body surface 206. Each array 210 is formed as patch that is attached to the device body 201 on the inner body surface 205 or the outer body surface 206, respectively. That is, in this embodiment, the arrays 210 of microstructures 211 are not part of the device body 201 . The patches forming the arrays 210 have a substantially elongate rectangular shape and are arranged at different circumferential positions on the inner body surface 205 and the outer body surface 206, having their long side aligned substantially parallel to the length extension of the tubular device body 201. Multiple arrays 210 can be arranged adjacent to each other along their long side to form a row of arrays 210.

[0088] The dimensions, shape and spacing of the microstructures 211 are substantially identical to the those of the embodiment shown in Fig. 2. That is, the microstructures 211 are micro-protrusions 212 formed by micro-cilia 213. However, in contrast to the microcilia 113 of the medical device 100 of Fig. 2, the micro-cilia 213 forming the microstructures 211 of Fig. 3 are inclined or more inclined. At hand, the micro-cilia 213 are angled relative to a respective base level 208, 208' of the inner body surface 205 and the outer body surface 206 by about 65 °. In particular, the micro-cilia 213 all are angled in substantially the same direction of the inclination. The direction of the inclination relative to the base level 208, 208' of the inner body surface 205 and the outer body surface 206 defines a general direction of fluid flow promoted by the arrays 210 of angled microstructures 211. With reference to the situation depicted in Fig. 3, the general direction of fluid flow promoted by the arrays 210 of angled microstructures 211 is from right to left.

[0089] Fig. 4 shows a third embodiment of the medical device 300 according to the invention. In principle, the medical device 300 of Fig. 4 is similar to the medical device 100 of Fig. 2. Therefore, similar or identical features are denoted by the same reference numbers, yet incremented by two hundred. Like the medical device 100 of Fig. 2, the medical device 300 of Fig. 4 comprises a substantially continuous array 310 of microstructures 311 , however, on both the inner body surface 305 and the outer body surface 306. Further in contrast to the medical device 100 of Fig. 2, the array 310 of microstructures 311 also covers those axial surface portions 305', 306' of the device body 301 comprising apertures 307. The microstructures 311 are also different in terms of shape, spacing and orientation. In Fig. 4, the microstructures 311 are micro-protrusions 312 formed as micro-pillars 313 which have an elongate pyramidal shape. At hand, the micro- pillars 313 have a height or length of 75 micrometer and a width of 25 micrometer as measured at the base level 308, 308' of the inner body surfaces 305 or the outer body surface 306, respectively. The inter-pillar distance (spacing) between adjacent micropillars 313 is 60 micrometers. Similar to the micro-cilia 213 of the second embodiment shown in Fig. 3, the micro-pillars 313 are angled relative to the respective base level 308, 308' of the inner body surface 305 and the outer body surface 306 by about 65 °. With reference to the situation depicted in Fig. 4, the direction of the inclination is from left to right.

[0090] Fig. 5 shows a fourth embodiment of the medical device 400 according to the invention. In principle, the medical device 400 of Fig. 5 is similar to the medical device 100 of Fig. 2. Therefore, similar or identical features are denoted by the same reference numbers, yet incremented by three hundred. At hand, the medical device 400 of Fig. 5 comprises a substantially continuous array 410 of microstructures 411 , 41 T on the inner body surface 405 and the outer body surface 406 which are formed by cutting or punching a plurality of isosceles triangles into the tubular device body 401 along a wedge-like cutting or punching line, and pushing the plurality of cut isosceles triangular elements inside the tubular device body 401 . As can be best seen in the enlarged window of Fig. 5, this process results in e a plurality of flat, isosceles-triangular micro-protrusions 412 which protrude from the inner surface at angle of about 45°. These micro-protrusions 412 may be considered as micro-sheds 413. As can be further seen in Fig. 5, the microprotrusions 412 all are angled in substantially the same direction of the inclination to promote a general direction of fluid flow thorough the body lumen 402, with reference to the situation depicted in Fig. 5 from left to right. On the outer body surface 406, the abovedescribed process results in a substantially continuous array 410' of microstructures 41 T in the form of micro-recesses 412', in particular micro-dimples 413', which have an isosceles-triangular cross-section shape are aligned in the same direction such that the axes of symmetry of the isosceles-triangular micro-recesses 412' are aligned substantially parallel to a length extension of the tubular device body 401. The microstructures 411 , 41 T extend across substantially the entire inner and outer surface 405, 406, apart from those axial surface portions 405', 406' comprising apertures 407. In use of the device, the microstructures 411 , 41 T are able to locally increase fluid-induced shear stress acting on the device body when applying an acoustic field to the medical device 400.

[0091 ] Fig. 6 shows a fifth embodiment of the medical device 500 according to the invention. In principle, the medical device 500 of Fig. 6 is similar to the medical device 300 of Fig. 4. Therefore, similar or identical features are denoted by the same reference numbers, yet incremented by two hundred. Like the medical device 300 of Fig. 4, the medical device 500 of Fig. 6 comprises a substantially continuous array 410 of microstructures 511 on both the inner body surface 505 and the outer body surface 506, which both extend across substantially the entire inner body surface 505 and outer body surface 506 (including those axial surface portions 505', 506' comprising apertures 507). As can be best seen in the enlarged window of Fig. 6, the microstructures 511 are microprotrusions 512 formed by micro-lamellae 513. At hand, the micro-lamellae 513 extend in the circumferential direction around the inner body surface 505 and the outer body surface 506, as kind of parallel discs or rings. In principle, it is also possible the microlamellae 513 extend around the inner body surface 505 and/or the outer body surface 506 in a helical configuration (not shown). The micro-lamellae 513 are angled relative to the inner body surface 505 and the outer body surface 506 by about 65 °and arranged in a staggered arrangement one behind the other along the length extension of the tubular device body 501. As a result of this, the micro-lamellae 513 are capable to promote a general direction of fluid flow through the body lumen 502 and along the outer body surface 506, with reference to the situation depicted in Fig. 6 from left to right. [0092] Fig. 7 shows a portion of a sixth embodiment of the medical device 600 according to the invention (see lower part of Fig. 7). The medical device 600 of Fig. 7 is similar to the medical device 200 of Fig. 3. Therefore, similar or identical features are denoted by the same reference numbers, yet incremented by four hundred. Similar to the embodiment of Fig. 3, the medical device 600 of Fig. 7 comprises a plurality of separate arrays 610 of microstructures 611 in the form micro-protrusions, in particular micro-cilia 613. At hand, the arrays 610 of microstructures 611 are provided as separate arrays 610, in particular patches of microstructures 611 , that are arranged on a band- or strip-like support member 610' carrying the arrays 610 of microstructures 611 (see upper part of Fig. 7). The band- or strip-like support member 610' is flexible allowing it to be wound up in a helical configuration such that the arrays 610 of microstructures 611 are either on the outside (see left middle part of Fig. 7) or the inside (see right middle part of Fig. 7) of the helical configuration. With the arrays 610 of microstructures 611 on the outside, the helical configuration may be arranged on an outer body surface 606 of a hollow device body 601 of the medical device 600 (see lower part of Fig. 7) such that the arrays 610 of microstructures 611 point outwards. The inner diameter of the helical configuration is chosen such that it matches the outer diameter of the hollow device body 601. In particular, it is possible that the band- or strip-like support member 610' is wound up in a helical configuration around the outer circumference of the hollow device body 601. Likewise, with the arrays 610 of microstructures 611 on the inside, the helical configuration may be arranged on an inner body surface of a hollow device body of a medical device (not shown in Fig. 7). In the configuration shown in the right middle part of Fig. 8, the band- or strip-like support member with the arrays 610 of microstructures 611 on its outside may advantageously be configured such that it is placeable inside the hollow device body of the medical device later on, in particular after the medical device has already been placed inside a human or animal body, for example by using a guide wire. For this, the outer diameter of the helical configuration is chosen such that it matches the inner diameter of the hollow device body. Like the medical device according to the first embodiment shown in Fig. 2, the entire device bodies 201 , 301 , 401 , 501 of the other embodiments shown in Fig. 3 to Fig. 7 - inclusive of the respective micro-structures 211 , 311 , 411 , 511 , 611 - are made of a non-magnetic material, for example, a polymer material. Thus, the respective micro-structures 211 , 311 , 411 , 511 , 611 show no kinematic response, if an alternating magnetic field was applied. Rather, cleaning is only achieved by applying an acoustic field to the medical devices 200, 300, 400, 500, 600, i.e. the cleaning mechanism promoted by the micro-structures 211 , 311 , 411 , 511 , 611 is only activated by sound.

[0093] Fig. 11 shows a seventh embodiment of the medical device 700 according to the invention. In principle, the medical device 700 of Fig. 11 is similar to the medical device 500 of Fig. 6. Therefore, similar or identical features are denoted by the same reference numbers, yet incremented by two hundred. Like the medical device 500 of Fig. 6, the medical device 700 of Fig. 11 comprises a substantially continuous array 710 of microstructures 711 on both the inner body surface 705 and the outer body surface 706, which both extend across substantially the entire inner body surface 705 and outer body surface 706 (including those axial surface portions 705', 706' comprising apertures 707). As can be best seen in the enlarged window of Fig. 11 , the microstructures 711 are microprotrusions 712 formed by micro-lamellae 713. At hand, the micro-lamellae 713 extend parallel to the length axis of the tubular device body 701 , i.e. parallel to a main direction of fluid low through or along the device body 701 , as kind of parallel rips along both the inner body surface 705 and the outer body surface 706. The micro-lamellae 713 have a substantially rectangular cross-section as seen in a plane perpendicular to their length extension, and protrude substantially perpendicular from the inner body surface 705 and the outer body surface 706, respectively.

[0094] Fig. 8 shows experimental results received from experiments with a Testing- Stent-on-Chip (TSoC) mimicking a ureteral stent with artificial biofilm and encrustation. The TSoC comprises a single rectangular micro-channel representing a tubular hollow body comprising arrays of micro-cilia on the inner body walls. The TSoC is bonded to a glass slide, which in turn is attached to a piezoelectric transducer and coupled to an electronic function generator and amplifier. The micro-cilia have a length of 100 micrometer, an inter-cilia distance (spacing) between adjacent micro-cilia of 80 micrometer, and a base width of 30 micrometer as measured at the base level of the cilia. In addition, the micro-cilia are angled relative to the respective base level of the inner body surface by about 65 °. This test-setup allows to test the flow profile of the deflectable micro-cilia and their efficacy in reducing encrustation and biofilm formation when activated by an acoustic field.

[0095] The images in the left column of Fig. 8 show the results of a first experiment used to investigate the capability of this micro-cilia to exert sufficient flow-induced shear stress onto the channel walls to clean the inner body surface representing the inner surface of a ureteral stent. The TSoC was perfused with a deionized water containing flow tracers (at hand polystyrene microparticles with 6 micrometer) at a flow rate of 30 microliter/min. During this process, the TSoC was angled along its longest axis to allow the flow tracers to enter the inter-cilia space by gravity. As can be seen in the image sequence in the left column of Fig. 8, taken by an inverted microscope, the flow tracers accumulated in cilia inter-cilia spaces before exposure to an acoustic stimulation (upper figure). Subsequently, an acoustic field with a frequency of 13.6 kHz was applied for a time of 5.25 sec. As a result, the polystyrene microparticles were flushed out by a steady streaming, resulting in the ciliated wall surface of the micro-channel being thoroughly cleaned.

[0096] In a second experiment, the TSoC was perfused with artificial urine and placed in an oven at 85 °C for two hours. Within this time, the fluid phase of the artificial urine evaporated, and only solid clusters of carbonate crystals remained in the micro-channel. To imitate urinary tract conditions (no air), the micro-channel was filled with deionized water and placed on the stage of an inverted microscope. The image sequence in the mid column of Fig. 8 demonstrates the acoustic response of the cilia encrusted with carbonate crystals in the inter-cilia space. After applying an acoustic field having a frequency of 99.6 kHz for a period of 6.88 sec, clustered carbonate crystals were detached, disintegrated and flushed away from the surface, indicating remarkable cleaning capabilities.

[0097] A third experiment was carried out to explore whether the cilia could still function effectively when fully encrusted. For the third experiment the same protocol as for the second experiment was followed, but with a different TSoC comprising cilia having a length of 20 micrometer, an inter-cilia distance (spacing) between adjacent micro-cilia of 50 micrometer, and a base width of 20 micrometer. In this setup, encrustations developed not only within the inter-ciliary space but covered the entire ciliary surface. As shown in the image sequence in the right column of Fig. 8, after applying an acoustic field having a frequency of 99.6 kHz for a period of 16.54 sec., a significant reduction in encrustation on the wall was observed. A second activation resulted in near-complete removal of the encrustation, showing the potential to clean even in critically encrusted scenario.

[0098] In a further experiment, with another TSoC mimicking a hollow body with side holes, a comparative analysis of the cleaning performances of surfaces with cilia and without cilia (i.e. smooth surfaces) was carried out. For this, carbonate crystals were placed on two different surfaces within the same micro-device: one with ciliated microchannels and another with non-ciliated microchannel walls. Results of this experiment are shown in Fig. 9, where the lower part of each image shows the non- ciliated wall-site and the upper part of each image shows the ciliated wall-site. After applying an acoustic field with a frequency of 99.6 kHz, the clustered crystal on the non- ciliated wall-site did not move and remained fully intact, proving the absence of powerful acoustically induced forces. Simultaneously, on the ciliated wall-site, a steady streaming was induced and increased shear stress was generated on the encrusted microchannel wall, resulting in a release of the crystals aggregation. A large crystal cluster was detached and further trapped within the vortex-like streaming. Suspended to the acoustic cilia induced micro-streaming, the crystal cluster was attracted towards the ciliary tips. At this wall-site, the crystal cluster was broken up, and its remaining debris was flushed away by a directional fluid flow. Overall, acoustic clearance was achieved within approximately 15.0 sec. These findings highlight the advantage of the micro-cilia as compared to smooth surfaces.

[0099] In yet a further experiment, it was demonstrated that the microstructures according to the present invention may enable an effective cleaning even in regions of stagnant flow, also known as dead cavity zones. In medicals stents and catheters, such dead cavity zones may be typically formed when intraluminal obstructions, e.g. stones or strictures, or extraluminal obstructions, e.g. due to tumors or pregnancy, impede fluid flow, creating stagnant zones, especially near side holes of the stent or catheter. Such regions of stagnant flow are particularly prone to encrustations and biofilm formation. Fig. 10 shows the results of experiments with a TSoC mimicking a hollow body with a dead zone near a side hole. After a buildup of encrusted surface with carbonate crystals, an acoustic field with a frequency of 99.6 kHz was applied. As shown in the image sequence of Fig. 10, the accumulated crystals in the cavity were dislodged within seconds and effectively cleared by a "tip-to-tip" streaming promoted by the micro-cilia.

[00100] This description and the accompanying drawings that illustrate aspects and embodiments of the present invention should not be taken as limiting-the claims defining the protected invention. In other words, while the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Various mechanical, compositional, structural, electrical, and operational changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the invention. Thus, it will be understood that changes and modifications may be made by those of ordinary skill within the scope and spirit of the following claims.

[00101 ] The disclosure also covers all further features shown in the Figs, individually although they may not have been described in the afore or following description. Also, single alternatives of the embodiments described in the figures and the description and single alternatives of features thereof can be disclaimed from the subject matter of the invention or from disclosed subject matter. The disclosure comprises subject matter consisting of the features defined in the claims or the exemplary embodiments as well as subject matter comprising said features. Also, the present disclosure covers intermediate generalizations of features or groups of features of the embodiments described and shown in the figures. I.e., specific features or groups of features as disclosed in the figures and the associated sections of the description may be combined with the more general embodiments of the invention disclosed in connection with the description of the invention. In particular, such specific features or groups of features may be provided in the more general embodiments of the invention in isolation from further specific features shown in the figures. It is understood that those skilled in the art are able to incorporate specific features from the description of the figures into the embodiments of the description of the invention.

[00102] Furthermore, in the claims the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit or step may fulfil the functions of several features recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The terms “essentially”, “about”, “approximately” and the like in connection with an attribute or a value particularly also define exactly the attribute or exactly the value, respectively. The term “about” in the context of a given numerate value or range refers to a value or range that is, e.g., within 20%, within 10%, within 5%, or within 2% of the given value or range. Components described as coupled or connected may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A medical device (100, 200, 300, 400, 500, 600, 700) for use as a ureteral stent, a biliary stent or a urinary catheter in a human or animal body (1 ), the medical device (100, 200, 300, 400, 500, 600, 700) comprising: a hollow device body (101 , 201 , 301 , 401 , 501 , 601 , 701 ) having at least one body lumen (102, 202, 302, 402, 502, 702), an inner body surface (105, 205, 305, 405, 505, 705) and an outer body surface (106, 206, 306, 406, 506, 706), wherein the inner body surface (105, 205, 305, 405, 505, 705) delimits the at least one body lumen (102, 202, 302, 402, 502, 702); at least one array (110, 210, 310, 410, 41 O', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) located on the inner body surface (105, 205, 305, 405, 505, 705) and/or the outer body surface (106, 206, 306, 406, 506, 606, 706) and configured to locally increase fluid-induced shear stress acting onto the device body (101 , 201 , 301 , 401 , 501 , 601 , 701 ) in use of the medical device (100, 200, 300, 400, 500, 600, 700) in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700).

2. The medical device (100, 200, 300, 400, 500, 600, 700) of claim 1 , wherein in use of the medical device (100, 200, 300, 400, 500, 600, 700) in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700) the at least one array (110, 210, 310, 410, 410', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 411 ', 511 , 611 , 711 ) is configured to generate locally increased shear stress onto the device body (101 , 201 , 301 , 401 , 501 , 601 , 701 ) of at least 0.001 Pa, in particular of at least 0.01 Pa, more particularly of at least 0.1 Pa or of at least 1 .0 Pa or of at least 10 Pa or of at least 100 Pa or of at least 500 Pa; or to generate locally increased shear onto the device body (101 , 201 , 301 , 401 , 501 , 601 , 701 ) in a range between 0.001 Pa and 500 Pa or between 0.01 Pa and 500 Pa, in particular between 1 Pa and 500 Pa or between 1 Pa and 100 Pa or between 1 Pa and 10 Pa.

3. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the at least one array (110, 210, 310, 410, 41 O', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) is configured to reduce or remove a contaminant from the inner body surface (105, 205, 305, 405, 505, 705) and/or the outer body surface (106, 206, 306, 406, 506, 606, 706) in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700).

4. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein in use of the medical device (100, 200, 300, 400, 500, 600, 700) the at least one array (110, 210, 310, 410, 410', 510, 710) of microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) is configured to locally modify fluid dynamics in proximity to the device body (101 , 201 , 301 , 401 , 501 , 601 , 701 ) in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700).

5. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein in use of the medical device (100, 200, 300, 400, 500, 600, 700) the at least one array (110, 210, 310, 410, 410', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) is configured to locally promote steady streaming in proximity to the device body (101 , 201 , 301 , 401 , 501 , 601 , 701 ) in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700).

6. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the at least one array (110, 210, 310, 410, 41 O', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) is configured to generate a fluid flow along the inner body surface (105, 205, 305, 405, 505, 705) and/or the outer body surface (106, 206, 306, 406, 506, 606, 706) in use of the medical device (100, 200, 300, 400, 500, 600, 700) in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700).

7. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the at least one array (110, 210, 310, 410, 41 O', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 411 ' , 511 , 611 , 711 ) comprises at least one of: an array (110, 210, 310, 410, 410', 510, 610, 710) of micro-protrusions (112, 212, 312, 412, 512, 612, 712), in particular an array (510, 710) of micro-lamellae (513, 713) or an array (110, 210) of micro-cilia (113, 213, 613) or an array (310) of micro-pillars (313) or an array of micro-sheds (413); and/or an array (410') of micro-recesses (412'), in particular an array of microgrooves or an array (410') of micro-dimples (413').

8. The medical device (100, 200, 300, 400, 500, 600, 700) of claim 7, wherein the micro-protrusions (112, 212, 312, 412, 512, 612, 712), in particular the microlamellae (513) or the micro-cilia (113, 213) or the micro-pillars (313) or the microsheds (413), have a tapered free end portion.

9. The medical device (100, 200, 300, 400, 500, 600, 700) of claim 7 or claim 8, wherein the micro-recesses (412'), in particular the micro-grooves or microdimples (413'), have a depth in a range between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 75 micrometers, for example 20 micrometer or 100 micrometer or 175 micrometers; and/or wherein the micro-protrusions (112, 212, 312, 412, 512, 612, 712), in particular the micro-lamellae (513, 713) or the micro-cilia (113, 213, 613) or the micro-pillars (313) or the micro-sheds (413), have a height or a length in a range between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 75 micrometers, for example 20 micrometer or 100 micrometer or 175 micrometers; and/or wherein the micro-recesses (412'), in particular the micro-grooves or microdimples (413'), have an inter-recess distance in a range between 1 micrometer and 400 micrometer or between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, for example 50 micrometer or 80 micrometer or 100 micrometers; and/or wherein the micro-protrusions (112, 212, 312, 412, 512, 612, 712), in particular the micro-lamellae (513, 713) or the micro-cilia (113, 213, 613) or the micro-pillars (313) or the micro-sheds (413), have an inter-protrusion distance in a range between 1 micrometer and 400 micrometer or between 1 micrometer and 200 micrometer or between 1 micrometer and 100 micrometers, for example 50 micrometer or 80 micrometer or 100 micrometers; and/or wherein the micro-recesses (412'), in particular the micro-grooves or microdimples (413'), have width in a range between 1 micrometer and 200 micrometers or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 50 micrometers, for example 20 micrometer or 30 micrometer or 40 micrometers; and/or wherein the micro-protrusions (112, 212, 312, 412, 512, 612, 712), in particular the micro-lamellae (513, 713) or the micro-cilia (113, 213, 613) or the micro-pillars (313) or the micro-sheds (413), have a width in a range between 1 micrometer and 200 micrometers or between 1 micrometer and 100 micrometers, in particular between 1 micrometer and 50 micrometers, for example 20 micrometer or 30 micrometer or 40 micrometers.

10. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the at least one array (110, 210, 310, 410, 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 511 , 611 , 711 ) comprises microstructures (111 , 211 , 311 , 411 , 511 , 611 , 711 ) angled relative to each other.

11 . The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the at least one array (110, 210, 310, 410, 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 511 , 611 , 711 ) comprises microstructures (111 , 21 1 , 311 , 411 , 511 , 611 , 711 ) angled relative to the inner body surface (105, 205, 305, 405, 505) and/or the outer body surface (106, 206, 306, 406, 506, 606, 706) by an angle greater than 0° and less than or equal to 90°, especially greater than 0° and less than 90°, in particular in a range between 20° and 80°, in particular 45° and 70°, for example by 65°.

12. The medical device (100, 200, 300, 400, 500) of any one of the preceding claims, wherein the device body (101 , 201 , 301 , 401 , 501 , 701 ) comprises at least one aperture (107, 207, 307, 407, 507, 707) extending from the outer surface through the device body (101 , 201 , 301 , 401 , 501 ) into the body lumen (102, 202, 302, 402, 502, 702), wherein the at least one array (210, 310, 510, 710) of microstructures (211 , 311 , 511 , 711 ) preferably comprises microstructures (211 , 311 , 511 , 711 ) located adjacent to the at least one aperture (207, 307, 507, 707).

13. The medical device (100, 200, 300, 400, 500) of claim 12, wherein a density of the microstructures (211 , 311 , 511 ) located adjacent to the at least one aperture (207, 307, 507) varies as a function of distance from the at least one aperture (207, 307, 507), in particular wherein the density of microstructures (111 , 211 , 311 , 411 , 411 ', 511 ) located adjacent to the at least one aperture (207, 307, 507) decreases with increasing distance from the at least one aperture (207, 307, 507).

14. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) are configured to move in response to applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700).

15. The medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims, wherein the at least one array (110, 210, 310, 410, 41 O', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 41 T, 511 , 611 , 711 ) is transparent to alternating magnetic fields, in particular wherein the at least one array (110, 210, 310, 410, 410', 510, 610, 710) of microstructures (111 , 211 , 311 , 411 , 411 ', 511 , 611 , 711 ) is made of a non-magnetic material.

16. A medical system (10), comprising: a medical device (100, 200, 300, 400, 500, 600, 700) of any one of the preceding claims; and an activation device (90) configured to be positioned externally of a human or animal body (1 ), wherein the activation device (90) comprises at least one sound transducer (91 ) configured to generate an acoustic field (93) to be applied from externally of the human or animal body (1 ) to the medical device (100, 200, 300, 400, 500, 600, 700).

17. The medical system (10) of claim 16, wherein the sound transducer (91 ) is configured to generate an acoustic field (93) with a frequency in a range between 1 Hz and 100 MHz, in particular between 1 kHz and 1 MHz, especially in range between 10kHz and 200kHz, or between 10kHz and 100kHz or between 20kHz and 100kHz; or above 20kHz or in the ultrasound range.

18. The medical system (10) of any one of claims 16 or 17, wherein the sound transducer (91 ) is configured to generate an acoustic field (93) at different frequencies and/or at different intensities.

19. The medical system (10) of any one of claims 16 to 18, wherein the sound transducer (91 ) is configured to generate an acoustic field (93) in a continuous mode and/or in a pulsed mode.

20. The medical system (10) of any one of claims 16 to 19, wherein the activation device (90) further comprises a power-control unit (92) for powering and controlling the sound transducer (91 ).

21. The medical system (10) of claim 20, wherein the power-control unit (92) is configured to control a directionality of the acoustic field (93) transmitted by the sound transducer (91 ).

22. The medical system (10) of any one of claims 16 to 21 , wherein the activation device (90) comprises a retaining structure configured to press the sound transducer (91 ) into abutment with the human or animal body (1 ).

23. The medical system (10) of claim 22, wherein the activation device (90) comprises a wearable device which comprises the retaining structure.

24. A method of acoustically activating a medical device (100, 200, 300, 400, 500, 600, 700) of any one of claims 1 to 15 during use in a human or animal body (1 ), in particular for cleaning purposes and/or mass transport, preferably using a medical system (10) of any one of claims 16 to 23, the method comprising applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700) from externally of the body of the human or animal body (1 ).

25. The method of claim 24, wherein the acoustic field (93) has a frequency in a range between 1 Hz and 100 MHz, in particular between 1 kHz and 1 MHz, especially in range between 10kHz and 200kHz, or between 10kHz and 100kHz or between 20kHz and 100kHz; or above 20kHz or in the ultrasound range.

26. The method of claim 24 or claim 25, wherein applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700) comprises applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700) at different frequencies and/or at different intensities and/or from different directions, in particular at different times.

27. The method of any one of claims 24 to 26, wherein applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700) comprises applying an acoustic field (93) to the medical device (100, 200, 300, 400, 500, 600, 700) continuously, in particular over a predetermined activation period; or intermittently, in particular in one or more pulses, such as trains of acoustic field pulses.