RU2719271C1 - Bubble sensor for detecting weak electric fields - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: use for registration of weak electric fields. Essence of the invention lies in the fact that the bubble sensor for detecting weak electric fields includes a sensor sensitive to the hydrophobic optically transparent material housing, which is a three-phase cavitation cell consisting of a shell – a high-viscosity hydrophobic liquid, in which there is a gas bubble with an outer diameter of 0.2–0.5 mm, containing at the interface gas-hydrophobic liquid, at least one water microinclusion ranging from 5 up to 20 mcm, wherein the cavitation cell is characterized by the presence of a negative charge on its surface and a positive charge in water microinclusions, and the housing is made with a magnifying lens to enable visualization and recording of the water microinclusion position.

EFFECT: possibility of detecting weakly varying quasi-static as well as constant electric fields with field strength of ≈3 V/cm.

6 cl, 5 dwg

Description

Technical field

The invention relates to measuring technique, namely to the registration of weak electric fields and can be used in biological and medical research as a compass of electric field sources in several directions at once.

State of the art

Registration of changes in weak quasistatic electric fields is currently an important and sought-after task in areas such as medicine, biology. There are many engineering methods for recording alternating electric fields, but all of them are based on amplification of the signal from the sensing element in the form of a small metal antenna by electronic means and require a power source. Such systems capture changes in the electric field at frequencies of several kilohertz and do not cover the region of quasistatic changes in the electric field. Important parameters here are sensitivity and small size, which allow the most accurate recording of ongoing processes.

In particular, a solution is known from the prior art regarding the measurement of electric field strength, based on the use of an electric field strength sensor containing a controlled dielectric with a dielectric constant that changes under the influence of an electric field (patent RU 2626065). Registration of the electric field is carried out by measuring the phase shift of the signal in the strip transmission line, on the basis of which the sensor is made. In order to reduce the size of the sensor, it can be made on the basis of the resonant segment of the transmission line, i.e. strip resonator. To expand the dynamic range, a sensor implementation is proposed on the basis of a system of interacting strip resonators, which, in essence, is a band-pass filter, in which the center frequency is tuned under the influence of an external electric field and the phase-frequency characteristic is shifted. Naturally, for this, the energy of the measured field is expended and the accuracy decreases.

It is known to measure the electric field by N pairs of sensing elements (RU 2388003). The sensor is made three-coordinate, i.e. n = 3, and it is oriented in space so that one of the components of the tension vector along one of the coordinate axes of the sensor becomes equal to zero, then, fixing the sensor in this position, turn the sensor around the found coordinate axis until two other components of the electric tension vector are equal fields along the coordinate axes of the sensor. In this case, the module of the vector of the measured electric field intensity is determined by measuring the algebraic sum of two non-zero components of the electric field vector of the electric field along the coordinate axes of the sensor. However, to determine the vector of the field source, the sensor must be rotated.

Also known is a sensor (probe) EZ-60x of the electric field of the company "Narda Safety Test Solutions S.r.l", made in Italy. Its description is presented on the Internet at: https://newpribor.ru/catalog/ispvtatelnoe-oborudovanie/probniki-polya/narda-pmm-ep-600-ер-601-ер-602-е_.html. The principle of operation consists in converting the three orthogonal components of the vector of the intensity of the alternating electric field from the metal pins to equivalent values of the alternating current voltage using an analog-to-digital converter (ADC), using an optical fiber cable and processing information on a computer. The disadvantage of such systems for measuring the electric field is the sensitivity only at high frequencies of field changes — tens of kilohertz, information processing on a computer, and, accordingly, the high cost of all equipment.

Closest to the proposed solution is a water-electric sensor for detecting weak physical fields and bio-radiation (Authors Ageev IM, Rybin Yu.M., Shishkin GG, Yeskin SM. "Water-electric sensors for detecting weak physical fields and bio-radiation" His description is available at: https://mai.ru/upload/iblock/d9c/vodoelektricheskie-datchiki-dlva-resistratsii-slabykh-fizicheskikh-poley-i-bioizlucheniya.pdf). The publication describes a sensor for measuring weak physical fields and biological objects, the operation of which is based on a change in the electrical conductivity of water when it is heated due to a change in the electric field strength. The sensor is a cell made of a dielectric material in the form of a flat parallelepiped with a volume of several milliliters with two electrodes for measuring the electrical conductivity of water, which depends on polarization by an external electric field. In the center of the sensor is a thermistor for measuring the temperature of water, which determines its electrical conductivity. The main disadvantage of such a sensor is both its size and the high sensitivity of water molecules in the microwave region and low sensitivity to weakly changing fields. The operation of such a sensor is ineffective in quasistatic fields. It is impossible to determine several sources of electric field on such a sensor, since their integral impact is measured.

A technical problem is the development of a sensor that works without the use of power sources and has small dimensions, characterized by high sensitivity to weakly changing fields.

Disclosure of Invention

The technical result of the invention is the possibility of creating a small-sized indicator and, based on it, a sensor of slightly varying quasistatic as well as constant electric fields with a field strength of ≈ 3 V / cm with a sensor element size of not more than 1 mm. For the operation of such an indicator and a sensor based on it, external power sources are not needed and it can simultaneously indicate the direction to several sources of electric field.

The technical result is achieved by developing a cavitation (or bubble) sensor for detecting weak electric fields, including a sensing element sealed in a housing of a hydrophobic optically transparent material, which is a three-phase cavitation cell, consisting of a shell - a highly viscous hydrophobic liquid in which a gas bubble is placed with an outer diameter of 0.2-0.5 mm, containing at least one gas-hydrophobic liquid at the interface, microinclusion of water rum from 5 to 20 μm, while the cavitation cell is characterized by the presence of a negative charge on its surface and a positive charge in the microinclusions of water, and the body is made with a magnifying lens to enable visualization and registration of the position of the microinclusion of water. The number of initial microinclusions of water in a gas bubble can reach 8 or more.

As a hydrophobic liquid, it is preferable to use a water-oil emulsion with a viscosity of 1-10 stock with a water content of from 0.1 to 0.5 vol. % In particular, silicone oil or PMS polymethylsiloxane is characterized by such parameters. Moreover, other liquids, for example, glycerin, characterized by a degree of transparency, which makes it possible to visualize microdroplets of water, can be used in the invention as a highly viscous hydrophobic liquid.

the periphery of the gas bubble. A sensitive element of this structure can be obtained with dimensions of 0.1-0.3 mm due to the use of the cavitation effect [R. Knepp. Cavitation // Mir, Moscow, 1974], in which gas bubbles are formed in a water-oil emulsion or oil emulsion with an insignificant water content in a liquid stream — dissolved in a liquid from the atmosphere. In this case, it is possible to obtain a sensitive element and large sizes up to 0.5 mm to more accurately determine the direction of the field source. The thickness of the shell is not fundamental in the design of the inventive sensor and may have a value of 0.2 mm or more due to the design of the sensor, in which it is intended to use this sensitive element. The sensitive element has its own electric field and is an electric compass of electric field sources.

In one embodiment of the sensor, a magnifying lens is placed on the housing from its outer side, in another, part of the housing surface is made in the form of a magnifying lens.

The inventive sensitive element is obtained by emulsification of the original hydrophobic liquid (water-oil emulsion), characterized by viscosity parameters from 1 to 10 stock, gas saturation at normal atmospheric pressure (about 764 mm Hg), water content from 0.1 to 0.5 vol. %, at a temperature of 17-22 ° C until the formation of a finely dispersed phase of water in a hydrophobic liquid, while cavitation bubbles form when the local pressure in the hydrophobic liquid decreases. Emulsification of the original hydrophobic liquid can be realized by any means and methods known from the prior art, for example, using the device shown in FIG. 5, where the flow of a water-oil emulsion placed in the outer cylinder is created by rotating this cylinder, in which the inner cylinder is placed near the wall of the outer cylinder (i.e., by sliding the inner cylinder on the inner surface of the outer cylinder). The size of the gas bubble is determined by the ratio of the radii of the aforementioned cylinders and the gap between them.

The method of detecting weak electric fields makes it possible to determine the change in the field over a length of 0.1 mm at a voltage of 3 V / cm. The method includes placing a sensor or a sensitive element near a detected source of electric field (weak electric fields are detected at a distance of about 1-4 cm from the sensitive element), and the presence of a weak electric field is detected by changing the initial form of microinclusion of water (mainly spherical to elongated), the direction of the field is determined by the direction of stretching of the microinclusion of water. When splitting microinclusions of water, an additional conclusion is drawn about the number of nearby sources of electric field by the number of splits in the bubble. The change in the position of the field source is associated with a change in the position of the water droplets on the surface of the gas-hydrophobic liquid interface in the cavitation bubble.

Thus, the sensitive element is an indicator of the electric field and is made in the form of a three-phase cavitation bubble with a shell of hydrophobic liquid with inclusions of microdrops of water. Such a formation is an electric dipole with a negative potential at the gas-liquid interface and a positive potential in microdroplets of water. Under the influence of an external electric field in such an indicator, microdroplets of water will be oriented in the direction of the gradient of the electric field. If there are several field sources, microdroplets of water will show orientation. Since the liquid almost always contains impurities of other liquids and dissolved gas, thus, a three-phase cavitation bubble can be used as an indicator (probe) of the electric field. Three-phase formation allows such a bubble to have its own electric field. It is formed by a negative charge at the hydrophobic liquid-gas interface and positive from microdroplets of water located at the same interface. Under the influence of an external electric field, an orientation occurs in the form of stretching a microdroplet of water in the direction of a negative field source. It has been established that three-phase cavitation formations react due to their field to the movement of neighboring ones. Each bubble “sees” a neighboring bubble with an angular resolution of up to 10 degrees. Thus, the use of three-phase cavitation formations makes it possible to register quasistatic electric fields in medicine and biology and can be used as an electric compass with the simultaneous registration of several sources of electric field. Distinctive features of the claimed invention from the prototype are a significant reduction in the size of the electric field indicator due to the small size of the cavitation bubble (0.2-0.5 mm), and the presence of its own electric field in a three-phase cavitation bubble eliminates the need for an external power source.

Brief Description of the Drawings

In FIG. 1 shows a micrograph of three-phase cavitation bubbles and a diagram of their interaction. On the central bubble, arrows indicate the orientations of positively charged microdrops of water 4 under the influence of electric fields of neighboring bubbles. When the position of the electric field source changes, the arrangement of the charged microdrop on the shell of the cavitation bubble changes.

In FIG. 2 is a series of photographs showing the movement of the “thickening” of a positively charged drop 4 in a three-phase cavitation bubble 1 under the action of the electric field of the neighboring bubble. The arrows indicate changes in the orientation of the microdroplets of water 4 in the bubbles during their mutual movement. The time interval between frames is 0.6 s.

In FIG. 3a is a photograph of a three-phase cavitation bubble, 3b is a reconstruction of a cavitation bubble, where the positions indicate: 1 cavitation bubble, 2 gas-hydrophobic liquid contact boundary, 3 silicone oil, 4 microdroplets of water at the gas-liquid boundary.

In FIG. 4 - a device with which a three-phase cavitation bubble can be obtained. Cavitation occurs in the region of minimum clearance H when the inner cylinder 7 slides along the inner surface of the outer cylinder 6 in the PMS100 hydrophobic liquid. After stopping the movement of the cylinder 6, the pressure in the gap H increases to atmospheric. This leads to the formation of a gas (cavitation) bubble with micro-impregnations of condensed water vapor at the gas-liquid interface.

In FIG. 5 shows the design of a three-phase cavitation sensor for practical use. The cavitation bubble 1 with the surrounding silicone oil 3 is placed in a small casing or cuvette (microcuvette) 8 made of a hydrophobic material and hermetically sealed on top of the lens 5 with a tenfold increase. With a cavitacinal vesicle size of 0.5 mm, such a lens will make it possible to record the locations of several microdrops of water 4 on the surface of the gas bubble 1.

The positions in the drawings indicate: 1 - a three-phase cavitation (gas) bubble, 2 - the interface (or contact) of the gas with a hydrophobic liquid, 3 - hydrophobic liquid (for example, silicone oil), 4 - microdrops of water, 5 - magnifying lens, 6 - external cylinder, 7 - internal cylinder, 8 - body / cuvette for placement of a three-phase cavitation bubble.

The implementation of the invention

The inventive sensitive element (indicator) of the electric field sensor is the result of cavitation in the form of bubbles in the gap between the eccentric cylinders when they slip in a highly viscous water-oil emulsion, for example, in the PMS 1000 hydrophobic oil. Cavitation bubbles contain dissolved atmospheric gas in which at the interface with the oil Condensed microdroplets of water are located. According to passport data, water is a by-product composition of oil in an amount of 0.05% by volume. A three-phase cavitation bubble of about 0.2 mm in size consists of a hydrophobic shell of highly viscous silicone oil, cavitation gas from the atmosphere and a small amount of water in the form of micron droplets between oil and gas. In such a bubble, a double electric layer is formed at the gas-silicone oil interface [A.P. Belyaev, V.I. Kuchuk. Physical and colloidal chemistry // GEOTAR-MEDIA, 2018.]. According to Ken’s rule, water, as the medium with the highest dielectric index, acquires a positive potential. Thus, a cavitation cell has both a negative charge on its shell and a positive charge inside, in the form of microdrops of water, and has its own electric field. In such a cell, microdroplets of water, due to their small size (5-20 microns), do not experience friction when moving along the surface of a hydrophobic liquid, conditions arise for its polarization and orientation in the form of thickenings in the direction of the gradient of the external electric field. Confirmation of this effect is shown in Fig 1. In the photograph, cavitation three-phase bubbles of 0.2 mm in size react to the electric fields of neighboring bubbles in the form of orientation and thickening of microdroplets 4, shown by arrows.

Light protrusions on the bubble are microdroplets of water, which, in the presence of several sources of electric field, are split and extended to the source of the field. In fact, such an indicator in a two-dimensional coordinate system is an electric compass and can indicate the angular location of other field sources with a resolution of 10 degrees. The sensitivity of such three-phase sensors is shown with mutual movement in FIG. 2. The left bubble is smaller than the right, has less condensed water vapor and is therefore lighter. Water droplets on both bubbles move at the gas-liquid interface, being oriented toward the center of an external source of electric field. In frames 1-3, the movement of the left bubble corresponds to 0.1 mm. In this case, the orientation of the water droplets in both bubbles changed, which characterizes the change in the external electric field at a distance of 0.1 mm.

A sensitive element can be manufactured by gas cavitation of an emulsion from a hydrophobic highly viscous liquid of 99.5% and 0.5% water by volume. Cavitation of the mixture occurs in a thin layer between non-concentric cylinders during their short-term sliding between themselves. This achieves a pressure drop sufficient for both gas cavitation and steam for boiling water (17 mm Hg) [Joseph D. D. Cavitation in a flowing liquid // Phys. Rev. E, 51, R1649 (1995)]. When the slip stops, the pressure rises to atmospheric pressure and condensation of water vapor into microdrops occurs in gas bubbles. A three-phase cavitation bubble is formed with a negative potential on its shell and positive in condensed water vapor. Due to the high viscosity, such a three-phase cavitation bubble almost does not float and can be placed in a hydrophobic body (cell or cuvette) (Fig. 5) with a magnifying lens for recording external sources of electric field. The hydrophobic body / cell / cuvette can be made of any optically transparent material with a hermetic placement of a three-phase cavitation bubble in it, while silicone oil acts as the shell of the cavitation bubble, filling the entire internal volume of the body. The lens can be mounted on the surface of the cell in any way known from the prior art, while a sensor embodiment is possible in which the entire body or part of its surface is made in the form of a magnifying lens. Such a sensor can have sizes from 3 to 5 mm.

Measurements showed that the proposed three-phase cavitation sensor is capable of sensing a change in the electric field strength over a travel length of 0.1 mm. The use of a three-phase cavitation bubble with its own electric field as an indicator, without an external power source, can be successfully used in areas such as medicine, biology, for example, for recording charged areas on a biological body, as well as an electric compass.

In an example of a specific implementation (Fig. 1-3), the inventive sensitive element is a cavitation bubble, was obtained using the device (Fig. 4). At the same time, in the experiment, PMS 100 was used as a hydrophobic liquid, the outer cylinder had a diameter of 5 cm, the inner one was 2.5 cm. The cylinders were placed coaxially in one another with a gap of H = 5-10 μm with the possibility of the inner cylinder sliding on the inner surface external cylinder, which was implemented by rotating the external cylinder about its axis, with a linear speed of 1 cm to 3 cm for 2-5 seconds, which provides the formation of gas (cavitation) bubbles with microincreations of condensed ditch water at the gas-liquid after stopping the movement of the outer cylinder. The diameter of the cavitation bubbles obtained was 0.2-0.5 mm. The results of the experiments, demonstrating the possibility of recording weak electric fields, the number of nearby sources of electric fields, directions of electric fields, are presented in FIG. 1-3, namely: using the manufactured sensitive element and a sensor based on it, weakly changing quasistatic fields were detected, characterized by the influence of neighboring cavitation bubbles, which have their own electric field. In addition, by filming, a change in the positions of microinclusions of water in the bubble was detected by the action of an external electric field of 3 V / cm, the source of which was placed at a distance of 2-3 cm of the sensing element. It should be noted that the sensor and the sensitive element are characterized by stability for a long time due to the preservation of gas in the oil shell, as well as microdroplets of water, due to their hydrophobicity, in the absence of sharp temperature changes, when the oil can freeze at low temperatures or become very hot and boil. In the study, under constant external conditions, the sensitive element retained its properties for at least 1 month.

Claims (6)

1. A bubble sensor for detecting weak electric fields, including a sensing element sealed in a housing of a hydrophobic optically transparent material, which is a three-phase cavitation cell, consisting of a shell - a highly viscous hydrophobic liquid, in which a gas bubble with an external diameter of 0.2-0 is placed , 5 mm, containing at the interface gas-hydrophobic liquid, at least one microinclusion of water ranging in size from 5 to 20 microns, while the cavitation cell is characterized by the presence of negative a substantial charge on its surface and a positive charge in the microinclusions of water, and the body is made with a magnifying lens to enable visualization and registration of the position of microinclusions of water. 2. The bubble sensor according to claim 1, characterized in that a water-oil emulsion with a viscosity of 1-10 stokes with a water content of 0.1 to 0.5 vol.% Is used as a hydrophobic liquid. % 3. The bubble sensor according to claim 1, characterized in that silicone oil or PMS polymethylsiloxane is used as the hydrophobic liquid. 4. The bubble sensor according to claim 1, characterized in that the gas bubble is cavitation, with gas dissolved in a liquid from the atmosphere. 5. The bubble sensor according to claim 1, characterized in that the sensitive element has its own electric field and is an electric compass of electric field sources. 6. The bubble sensor according to claim 1, characterized in that the magnifying lens is placed on the housing from its outer side.

Images