DE102007060352A1 - Device for electronically compatible thermal controlling of integrated micro-systems on basis of active temperature sensitive hydraulic gels, has component, which produces temperature field - Google Patents

Abstract

The device has a component, which produces a temperature field (3) and is placed on or in the proximity of the upper side of a substrate (1). The substrate serves as a defined thermal resistance, whose lower side is kept constant by an active temperature control unit (2) on a certain base temperature. The work temperature area has device in a phase transition area of the temperature sensitive hydraulic gels, which is necessary for implementation of the technical functions of the component.

Description

introduction

The The invention relates to devices for electronics-compatible control integrated active microsystems based on temperature-sensitive Hydrogels with a high density of active elements.

State of the art

Analogous to the development of microelectronics, in microsystems technology highly integrated systems are expected to undergo exorbitant technological advances, above all in the key technologies of biotechnology, medical technology and molecular biology. Some scientists even consider integrated microsystem technology to be "21st century technology." The property profiles of the two highly integrated micro-technologies available, silicon-based microsystem technology and micro-pneumatic polymer-based microfluidics, can not necessarily be expected to bring about a major technological revolution The silicon-based technology, including various hybrid technologies that integrate, for example, piezo or shape memory actuators, is suitable almost exclusively for individual applications of high-quality, highly integrated systems, whose biggest success so far is mirror array systems [ van Kessel, PF, Hornbeck, LJ, Meier, RE & Douglass MR Proc. IEEE 1998, 86, 1687-1704 ]. Even the more cost-effective micropneumatic technology requires complex structures ( WO 2004 028 955 . WO 01/001025 ), which in addition to the actual microfluidic level still include one or more pneumatic control levels and zen due to device-technical limitation of the pneumatic control line number the disadvantage of only indirect, sequential addressability of the active elements, each with a row and column multiplexer. In addition, only a single basic function, namely that of closing or displacing, can be realized.

easiest Functional structures can probably only be realized with one material, which is similar to microsystem technology suitable property profile as the silicon for the Microelectronics owns.

Materials which, because of their multifunctionality and their processability and structurability potentially correspond to this aspect, are stimuli-sensitive hydrogels. They offer a wealth of sensory, actoric and other active basic functions. Their initially problematic electrical drivability was made possible by the development of a thermal-electronic interface using temperature-sensitive hydrogels and implemented in a series of fluidic basic elements ( DE 101 57 317 A1 , [ A. Richter et al., J. Microelectromech. Syst. 2003, 12, 748-753 ] DE 10 2004 062 893 A1 ). The excellent miniaturization of the hydrogel elements is demonstrated in tactile displays ( DE 102 26 746 A1 ), Delivery arrays ( DE 10 2004 061 732 A1 ), programmable micro-stamps ( DE 10 2004 061 731 B4 ), microfluidic systems ( DE 10 2006 020 716 A1 . WO 2006/038159 A1 ) to realize complex systems with a variety of active hydrogel elements exploited. The thermal-electronic interface is based either on heating resistor structures which are arranged in close proximity to the individual hydrogel elements, or on the use of high-energy light, for. B. in the form of a laser whose energy is converted by absorption into thermal energy. The laser may include a line laser, which controls the pixels periodically, but also a laser, which drives the individual pixels by means of mirrors.

Lots of these microsystems offer significant benefits only if if they are more highly integrated, d. h., a high density own active components. But this is with the hitherto existing Engineering booth not suitable for hydrogel-based microsystems reach, as the described thermal drives rule not once approaching the necessary resolution. Due to the effect of heat propagation are component distances less than 2 mm virtually impossible to realize. This is because of that usually less heat over the surface of the microsystem delivered to the environment as supplied and it becomes a holistic warming of the system comes.

Object of the invention

task The invention is therefore a device for electronics compatible thermal-electrical control to create the realization highly integrated micro-technical systems based on temperature-sensitive Materials, especially temperature-sensitive hydrogels allows.

Description and examples

According to the invention the object is achieved by the features specified in claim 1. Advantageous embodiments are in the claims 2 to 15 indicated.

The Principle of the invention consists in the temporal and spatial defined control of a temperature-sensitive multicomponent system through a temperature field. The temperature field control has the advantage that all components are inside the spatially defined Temperature field can be influenced simultaneously. The exact assignment a drive element to a controllable component is not more necessary, so that significantly more and also simpler technical Possibilities for the realization of the control exist. An essential requirement of temperature field control is the T-field stabilization by dissipation of excess Heat by active temperature control. The resolution and the achievable temperature differences, can be constructive by the nature and thickness of the substrate material and by the Determine the temperature field generating energy input.

By the temperature of the tempering can also be the location of the temperature working range.

The Invention is intended to be closer to some embodiments be explained. In the accompanying drawings demonstrate:

1 the basic configuration of a temperature field controller for temperature-sensitive multicomponent systems,

2 Two possible embodiments of the temperature field control for the light-optical control of the components of microsystems

3 the achievable temperature difference between the top and bottom of the substrate as a function of substrate thickness,

4 the temperature profile at the boundary of the temperature field for a 500 μm thick polyester substrate and light-optical control on the basis of a commercial video projector with a 200 W lamp,

5 a temperature field control with a video projector as a light source,

6 a temperature field control based on a large-format transmission TFT display panel

7 a temperature field control based on a resistor array

8th the temperature-dependent swelling behavior of poly (N-isopropylacrylamide),

9 the matrix of a tactile display with pixels based on poly (N-isopropylacrylamide)

10 the response time of a poly (N-isopropylacrylamide) -based actuator with light-optical control of different effective heating power.

Representative of further application and design options is based on 1 presented the basic structure and the mode of action of the temperature field-based control. Constructional and operational influence possibilities on the characteristics of the control clarify the 2 to 4 , The 5 to 7 introduce some particularly advantageous designs for high-resolution temperature field controls. In the 8th to 10 the control of a microsystem with components based on temperature-sensitive hydrogels is presented.

As 1 illustrated, is in the inventive control on the surface of the substrate ( 1 ) by corresponding energy input a spatially and temporally defined temperature field ( 3 ), which has at least one temperature T _{W, U} and at most one temperature T _U. The preferred active temperature control ( 2 ) tempered the underside of the substrate ( 1 ) to the base temperature T _B , dissipates the excess heat and keeps the temperature field ( 3 ), which is here dolphin-shaped, over the desired period constant. The temperature control ( 2 ) also guarantees an extensive system independence from the ambient temperature.

To two adjacent components ( 16 ) safely into the two opposite final states ( 16a . 16b ), they must have a minimum distance Δx _W (see 2 ), which corresponds to the resolving power of the drive. For array arrangements, the minimum grid dimension x _R = x _K + Δx _{W is also} important.

These distances are determined by the in 3 shown temperature profile at the boundary of the temperature field determined. It has three areas. The heated substrate area ( 3 ) inside the temperature field has a maximum temperature T _U. The unheated area ( 4 ) has the base temperature T _B at a distance x _B. To the components ( 16 ) to safely control between their final states, the working temperature difference .DELTA.T _W must be realized. The lower limit of the temperature field to which the components ( 16 . 16a ), the temperature is T _{W, U.} The upper temperature limit, up to which the components ( 16 . 16b ) are not driven, T _{W, B forms} .

The working temperature range ΔT _W should preferably be in the approximately linear range of the temperature curve, since in this case the smallest possible Δx _{W is} achieved. It is therefore advisable to choose the temperature difference T _U - T _B correspondingly large. It is also advantageous that Δx _W decreases further as the T _U - T _B increases, since the increase in the approximately linear temperature curve range increases. The dissolving power can be influenced by the substrate thickness d _S and the effective applied heating power P _H for the same substrate material. A reduction of the substrate thickness causes a reduction of .DELTA.x _W , but in this case to achieve a respective same temperature of the field ( 3 ) the heating power can be increased. An increase in the heating power P _H at constant substrate increases the temperature difference T _U - T _B with the consequences already described.

kann die Differenz zwischen oberer (T_U) und Basistemperatur T_B durch die Dicke d_S des Substrates und die Wärmeleitfähigkeit λ_S des Substratmaterials konstruktiv voreingestellt werden. 4 zeigt die Abhängigkeit der Temperaturdifferenz ΔT = T_U – T_B von der Dicke d_S des Substrates (1) aus Polyester bei einer applizierten effektiven Heizleistungsdichte von 0,4 Wcm^–2. Zum Erzielen großer Temperaturdifferenzen sollte die Wärmeleitfähigkeit λ_S des Substratmaterials möglichst gering sein. Viele Polymere, wie z. B. Polyester, Polymethyl-Methacrylat, Polyamid, Polykarbonat, Polystyrol, Polybutylen-Terephthalat und Polydimethylsiloxan, verfügen über Wärmeleitfähigkeiten im Bereich zwischen 0,14 und 0,22 W/m·K und eignen sich deshalb potenziell als Substratmaterialien.According to the laws of heat propagation

the difference between the upper (T _U ) and base temperature T _B can be preset in terms of design by the thickness d _{S of} the substrate and the thermal conductivity λ _{S of} the substrate material. 4 shows the dependence of the temperature difference ΔT = T _U -T _B on the thickness d _{S of} the substrate ( 1 ) of polyester at an applied effective heat density of 0.4 Wcm ^-2 . To achieve large temperature differences, the thermal conductivity λ _{S of} the substrate material should be as low as possible. Many polymers, such as. As polyester, polymethyl methacrylate, polyamide, polycarbonate, polystyrene, polybutylene terephthalate and polydimethylsiloxane have thermal conductivities in the range between 0.14 and 0.22 W / m · K and are therefore potentially suitable as substrate materials.

Of the spatially defined entry of the heating power on the substrate surface can be done with different technical principles. Essentially can be electronic systems, which are capable to the extent required a spatially defined (Heating) energy input to realize in optical and resistive devices organize.

Optical drives are based on the conversion of light energy into heat energy through absorption. This energy conversion takes place either on the surface of the substrate ( 1 ), in the component to be controlled ( 9 ) itself or on a body surface of the component. It is recommended that the surface of the substrate ( 1 ), to provide the component to be controlled or the body surface with pigments whose color optimally absorbs the wavelength or the working wavelength spectrum of the light source. Optical actuators can be classified into three types: those with projection systems as light sources, large-format transmission screens for structuring undirected light, and single-laser systems with the direct or indirect ability to be directed to any point in the microsystem.

Projection systems are potentially laser projectors, liquid crystal display (LCD) and micromirror devices (DMD). 5 shows an optoelectronic drive based on a commercially available video projector EPSON EMP-820 as a light projection system ( 5 ). This device has a 200 W lamp ( 6 ) and 0.9 '' micro-transmission liquid crystal displays ( 7 ). The transmission liquid crystal displays function as optical masks. The transparency of a liquid crystal pixel and thus its projected brightness or light output are controlled by influencing the polarization direction of the light. For parallelizing the light beam ( 8th ) comes an optic ( 9 ), consisting of a convex lens with f ₁ = 90 mm and a lens with f ₂ = 80 mm used. With this arrangement, the in 4 represented temperature difference ΔT = T _U - T _B between the blackened surface ( 17 ) of a polyester substrate ( 1 ) and the one with ( 2 ) on T _B tempered substrate underside depending on the substrate thickness. For a substrate thickness of 500 μm ΔT = 13 K is achieved. If the base temperature is controlled by the temperature control ( 2 ), which in the case described is an active water tempering, kept at 26 ° C, the results in 3 Temperature curve shown at the temperature field boundary. The resolving power of the control Δx _W in this case is 600 μm.

The conversion of light into heat energy can be achieved by the use of absorber materials ( 17 ) effectively. As 2 illustrated, for this purpose, the substrate ( 1 ) are colored with a color which reflects the light of the source ( 6 ) absorbed particularly well. For normal, white light is suitable for a black color. Alternatively, in the component material ( 16 ) also pigments ( 17 ) of appropriate color. The absorber materials do not necessarily have to be placed on the substrate. If the controllers are operated as basic units for exchangeable microsystems, it is recommended that the absorber structures ( 17 ) to integrate into the microsystems, especially if the absorber materials individual components, eg. B. microvalves, are assigned directly. Structured blackened polyester films can be, for example, TypoPhot TO-G films, as used in lithography.

Micromirror devices project the light from a source by reflection onto an image plane. Depending on the inclination of each micromirror on the DMD chip, the light is either directly to the optics or imaging plane reflected or directed to an absorber, d. h., every single one Pixel can be fully illuminated or hide. Leave any brightness between these extremes can be achieved by a pulse width modulated mirror drive. Due to the edge length of a single mirror of about 12 microns can be with the DMD technique and a relative low imaging ratio drives with highest Realize resolution. Because the DMD chips according to the manufacturer in water cooling pictures with up to can project to 40,000 lm, allows the DMD technique also in terms of performance one such Business.

6 illustrates a light-optical control device for complex microsystems, which is based on large-sized and high-intensity transmission liquid crystal displays. Such devices enable drives that, in extreme cases, allow direct pixel-to-component mapping through a 1: 1 aspect ratio and are potentially capable of handling millions of components ( 16 ) to control. It is recommended to use monochrome transmission thin film transistor liquid crystal displays such. For example, the NL160120AM27 series from NEC LCD Technologies offers high contrast and more than three times better brightness compared to color TFT displays, resulting in low transmission losses. Such a system can be designed as a control unit and comprises, in addition to the display ( 13 ) a lamp ( 6 ), which may be a continuous lamp, but also a stroboscope. The light beam ( 8th ) can by an optics, not shown, for. B. in the form of a Fresnel lens, parallelized and homogenized. The temperature field at the surface of the substrate ( 1 ) is masked by appropriate masking of the light of the lamp ( 6 ) through the transmission display ( 13 ) reached. The temperature control ( 2 ) ensures the base temperature of the substrate, dissipates excess heat and simultaneously cools the transmission display ( 13 ). The display ( 13 ) and thus the temperature field is controlled by an electronic control ( 10 ), z. As a computer controlled. Since display and computer are standard components, conventional interfaces and data formats can be used.

Single Laser Systems are mostly based on commercially available systems, so z. As optical tweezers. They are also suitable in principle for optical controls, as they use high energy light defined wavelength in spatially exactly defined Can muster way. However, the equipment is very expensive and expensive.

The supposedly simplest design is offered by resistive drive systems, such as one example 7 is shown. The resistive drive can be executed in thin-film technology and based on conventional thin-film transistor (thin film transistor TFT) matrices. The resistive panel ( 15 ) must either be on the surface of the substrate ( 1 ) or take over its function. The bottom of the arrangement is again by the temperature ( 2 ) tempered.

The temperature field control according to the invention is intended in particular for active microsystems with components based on temperature-sensitive hydrogels. Temperature-sensitive hydrogels are representatives of the "stimuli-sensitive" or "smart" hydrogels [ A. Richter, hydrogel-based μTAS. In CT Leondes: MEMS / NEMS HANDBOOK: Techniques and Applications. vol. 2, chapter 5, pp. 141-171, Springer-Verlag New York 2006 ]. According to the prevailing bonding conditions, temperature-sensitive hydrogels can be classified into chemically cross-linked and physically cross-linked hydrogels. Chemically or covalently crosslinked temperature-sensitive hydrogels have the ability to perform a discontinuous reversible volume phase transition with temperature changes. They change their volume from the swollen to the swollen state by up to 99% with release of the swelling agent, which is watery in nature. There are two types of behavior to distinguish. Hydrogels with a lower critical solution temperature (LCST) are swollen below a phase transition temperature and escape when they are exceeded. Gels which have an upper critical solution temperature are swollen above this temperature and swell when they fall below this temperature. Temperature-sensitive, physically cross-linked or "thermoreversible" hydrogels become entangled or desiccated when critical temperatures are reached, ie they gel or dissolve [[ K. te Nijenhuis, Thermoreversible Networks, Adv. Polym. Sci. 130, Springer-Verlag Berlin, Heidelberg, New York 1997 ].

For the active components of high-integrated microsystems are special covalently cross-linked temperature-sensitive hydrogels interesting because These can be operated several times.

These hydrogels are able to drastically change their volume swelling with a very small temperature change. 8th represents the temperature behavior of the temperature-sensitive hydrogel poly (N-isopropylacrylamide) as a function of temperature. To change the hydrogel from the swollen to the swollen state or vice versa, only a temperature difference of 6K (29 ° C to 35 ° C) must be realized. This temperature difference can be realized with the temperature field control easily with the required resolution. This clarifies 9 , There, the height profile of a matrix of actuators based on poly (N-Isopropylacrylamid) is shown, which with the in 1 schematically illustrated dolphin-shaped temperature field ( 3 ) was driven. The actuators have edge lengths of x _K = 400 microns and a distance of 180 microns with a grid of 580 microns. The necessary resolution Δx _W = 180 microns was achieved with a 600 W lamp, a blackened polyester substrate of thickness 500 microns and a base temperature of 26 ° C. The actuators have a height of 250 μm in the controlled state and a height of approx. 500 μm outside the temperature field.

It It should be noted that temperature-sensitive components of microsystems may also be based on meltable substances. Materials that are in the range of room temperature, for example between -20 ° C and + 120 ° C by temperature action to an aggregate state change between liquid and solid or liquid and highly viscous (insignificant flow properties) can be stimulated, are, for example, oils and fats, paraffins or alkanes or waxes. Semi-solid paraffins or soft paraffin have z. B. melting temperatures between 45 ° C and 65 ° C, Petrolatum or Vaseline has melting temperatures in the range from 38 ° C and 60 ° C. Other temperature sensitive Components may be based on shape memory alloys, z. Nitinol based.

A light-optically generated temperature field (eg with a video projector) builds up completely within a few hundred milliseconds and is at least able to image slowly moving images or control patterns in real time as a temperature field. It is usually much faster than the response times of the components to be controlled. As 10 clarifies their response time depends on the effective applied heating power. This in turn is determined by the temperature difference T _U - T _{W, U.} The higher this is, the shorter the response times of the hydrogel components.

The Temperature field does not have a contiguous area be. Especially in microfluidic processors, the temperature field be a variable control pattern, with individual areas of the control pattern or temperature field also on different Temperatures, which is important about components in positions between their final states to be able to hold. Allow such temperature differences with light-optical transmission-based annotations due to changes the display transparency, in mirror systems, for example by the illumination frequency (both affect the "brightness"), and in resistive driving by adjusting the heating power to reach.

The Temperature field-based control allows the realization more highly integrated microsystems, especially hydrogel-based, by having the necessary dissolving power and provides the necessary technology. So can now tactile displays, controllable stamps for microcontact printing, Arrays of many memory cells, valve arrays, pump systems, hydrogel-based surfaces, mirror arrays, microfluidic processors etc. with the required resolution and required Degree of integration.

1

substratum

2

tempering

3

Temperature field, heated substrate surface

4

Unheated substrate surface

5

Light projection system

6

lamp

7

Micro-transmissive liquid crystal display

8th

beam of light

9

optics

10

electronic control

11

to controlling microsystem

12

microsystems with control

13

Transmission TFT liquid crystal display

14

control unit

15

resistive panel

16

component

16a

heated, controlled component

16b

unheated, uncontrolled component

17

absorber

P _H

Heating capacity, effectively applied

.DELTA.T

maximum temperature difference

ΔT _W

Processing temperature range

T _B

base temperature

T _U

maximum temperature

T _{W, U}

Upper working temperature

T _{W, B}

Lower working temperature

d _S

substrate thickness

f

focal length

Δx _W

Resolving power, minimum component distance

x _B

Distance at which the substrate surface has the base temperature T _B

x _K

component width

x _R

Pitch

x _U

Distance between x (T _U ) and x (T _{W, U} )

λ _S

thermal conductivity

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2004028955 [0002]
• WO 01/001025 [0002]
• - DE 10157317 A1 [0004]
• DE 102004062893 A1 [0004]
• - DE 10226746 A1 [0004]
• DE 102004061732 A1 [0004]
• DE 102004061731 B4 [0004]
• DE 102006020716 A1 [0004]
• - WO 2006/038159 A1 [0004]

Cited non-patent literature

• van Kessel, PF, Hornbeck, LJ, Meier, RE & Douglas MR Proc. IEEE 1998, 86, 1687-1704 [0002]
• A. Richter et al., J. Microelectromech. Syst. 2003, 12, 748-753 [0004]
• - A. Richter, hydrogel-based μTAS. In CT Leondes: MEMS / NEMS HANDBOOK: Techniques and Applications. vol. 2, chapter 5, pp. 141-171, Springer-Verlag New York 2006 [0035]
• K. te Nijenhuis, Thermoreversible Networks, Adv. Polym. Sci. 130, Springer-Verlag Berlin, Heidelberg, New York 1997 [0035]

Claims (14)

Device for electronically compatible thermal control of integrated microsystems based on active temperature-sensitive hydrogels, characterized in that at least one component ( 15 . 17 ), which can generate a temperature field, on or near the top of a substrate ( 1 ), which serves as a defined thermal resistance, the underside of which by an active tempering ( 2 ) is kept constant at a certain base temperature T _B , the operating temperature range ΔT _{W of} the device essentially comprising the phase transition region of the temperature-sensitive hydrogels used for realizing the technical functions of the components ( 16 ) necessary is. Device according to claim 1, characterized in that for a given effective heating power P _H the difference .DELTA.T between maximum temperature T _U and base temperature T _B by the thickness d _S and the thermal conductivity λ _S serving as a thermal resistance substrate material ( 1 ) is structurally determinable. Device according to Claim 1, characterized in that, given the effective heating power P _H, the dissolving power Δx _{W is} determined by the thickness d _S and the thermal conductivity λ _{S of} the substrate material serving as thermal resistance ( 1 ) is structurally determinable. Device according to Claim 1, characterized in that the temperature-field-generating component ( 15 ) Based on resistive elements, which z. B. electrical resistors, which are made in thick-film technology, or operated as resistors thin-film transistors may be. Device according to Claim 1, characterized in that, in the case of light-optical control, the heating structures are replaced by light-absorbing structures ( 17 ) are formed, for. B. in the form of structured or unstructured color coatings of the substrate ( 1 ) or the microsystem ( 11 ), but also pigmented hydrogel elements ( 16 ). Device according to Claim 1, characterized in that, in the case of light-optical control, the light-absorbing structures ( 17 ), z. B. in the form of structured or unstructured color coatings of the substrate ( 1 ), but also pigmented hydrogel elements ( 16 ) Components of the microsystem ( 11 ) are. Device according to claim 5 and 6, characterized that as a color-coated substrate commercially available photolithographic Mask material is used, for. B. TypoPhot TO-G films. Device according to claim 1, characterized in that the temperature field ( 3 ) generating light beam by video projection systems, in particular laser projectors, based on micro-transmission liquid crystal displays ( 7 ) or micromirror devices. Device according to claim 1, characterized in that the temperature field ( 3 ) generating light beam by large-sized transmission liquid crystal displays ( 13 ) is controlled. Device according to Claim 1, characterized in that, in the case of light-optical drives, the light beam ( 8th ) by a suitable optics ( 9 ) is parallelized and homogenized in intensity. Device according to claim 1, characterized in that the base temperature T _{B of} the temperature ( 2 ) is adjustable. Device according to claim 1, characterized in that the temperature ( 2 ) is a control and thus ensures a constant base temperature T _B. Device according to claim 1, characterized that the device for electronically compatible thermal driving Part of the controlled micro-system is to be controlled. Device according to claim 1, characterized in that the device for electronically compatible thermal activation as an independent device for operating integrated microsystems ( 11 ) based on temperature-sensitive hydrogels, so that the microsystems ( 11 ) are interchangeable.