CN110763256B - Polydimethylsiloxane film, flexible capacitive sensor and preparation method thereof - Google Patents
Polydimethylsiloxane film, flexible capacitive sensor and preparation method thereof Download PDFInfo
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
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Abstract
本发明属于柔性传感器领域，并公开了聚二甲基硅氧烷薄膜、柔性电容传感器及其制备方法，该传感器包括上电极层、中间电介质层和下电极层，上和下电极层结构相同，均包括柔性基体材料和镶嵌在基体材料中的液态金属；中间电介质层介于上和下电极层之间，其中具有多层阶梯介孔微结构，同无该介质层的柔性电容传感器相比，改善了柔性电容传感器的线性度；当传感器受到压力或被导体靠近时，通过测量传感器电容的变化获得该传感器受到的压力或导体与传感器之间的距离的大小。本发明还公开了该传感器的制备方法。通过本发明，设计出基于液态金属电极及多层阶梯介孔微结构的电介质层的柔性电容式传感器，实现柔性传感器的高灵敏度。
The invention belongs to the field of flexible sensors, and discloses a polydimethylsiloxane film, a flexible capacitive sensor and a preparation method thereof. The sensor comprises an upper electrode layer, an intermediate dielectric layer and a lower electrode layer, and the upper and lower electrode layers have the same structure, Both include a flexible base material and a liquid metal embedded in the base material; the intermediate dielectric layer is between the upper and lower electrode layers, and has a multi-layer stepped mesoporous microstructure. Compared with the flexible capacitive sensor without the dielectric layer, The linearity of the flexible capacitive sensor is improved; when the sensor is subjected to pressure or is approached by a conductor, the pressure on the sensor or the distance between the conductor and the sensor is obtained by measuring the change in the capacitance of the sensor. The invention also discloses a preparation method of the sensor. Through the present invention, a flexible capacitive sensor based on a liquid metal electrode and a dielectric layer with a multi-layer stepped mesoporous microstructure is designed to achieve high sensitivity of the flexible sensor.
Description
Technical Field
The invention belongs to the field of flexible sensors, and particularly relates to a polydimethylsiloxane film, a flexible capacitive sensor and a preparation method thereof.
Background
With the development of science and technology and society, robots have gradually advanced into daily life from the aspects of scientific research, industrial automation, medical treatment and the like. Moreover, the emerging of emerging robots puts higher requirements on equipment hardware, and flexible sensors are a popular emerging research field for the development of modern electronic systems due to good flexibility and stretchability, and a series of electronic products with powerful functions, such as electronic skins, medical implant equipment, bionic artificial limbs, man-machine interaction interfaces, non-invasive personal health monitoring electronic equipment and the like, are developed by combining frontier interdisciplines such as biomechanics, medical engineering, computer technology, robot technology and the like. Flexible devices have their own strong advantages in terms of weight reduction, reliability, etc. compared to earlier rigid connection assemblies, which is the main reason for the rapid development of flexible electronic devices. The flexible electronic device can be deformed into a complex shape by stretching, compressing, bending, twisting and the like, and still keeps higher reliability, excellent functions and integration level under the action of external force. These flexible electronic products also face a number of challenges, such as low sensitivity, small dynamic range, etc. The traditional capacitive sensor has the advantages of high sensitivity, good dynamic response, higher resolution and the like, is widely applied to measuring physical parameters such as displacement, acceleration, pressure and the like, and cannot meet the requirements in the aspects of shape retention, flexibility, stretchability and the like. Compared with the traditional capacitive sensor, the flexible capacitive sensor has the advantages of good stretchability, shape retention and flexibility, can be used for detecting on a complex surface, and is widely applied to the fields of electronic skin, contact measurement, flexible antennas, biosensors and the like. High accuracy, high resolution and high flexibility are hot spots in the research of flexible capacitive sensors. How the three features are compatible is the focus of current research. Typical flexible capacitive sensors can increase resolution by reducing the electrode width and the distance between the two plates, but this will reduce the capacitance capacity and result in a lower signal-to-noise ratio. Meanwhile, due to the influence of various electrical noises such as wires and circuit boards, it becomes more difficult to measure the minute pressure.
At present, flexible electronic skin of a fully flexible and multifunctional robot is mostly focused on touch sensing, but the approach sensing capability is adopted, and the reaction cannot be made when an acting object approaches.
The flexible electronic technology is separated from the solid electronic technology, so that the traditional semiconductor process is also adopted in a large amount, but the adaptability of some flexible materials to the traditional process is not good, so that the improvement of the process is necessary, and the invention provides the high-sensitivity flexible capacitive sensor and the preparation method thereof.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a high-sensitivity flexible capacitance sensor and a preparation method thereof.
To achieve the above object, according to the present invention, there is provided a high-sensitivity flexible capacitive sensor characterized by comprising an upper electrode layer, an intermediate dielectric layer and a lower electrode layer, wherein:
the upper electrode layer and the lower electrode layer have the same structure and both comprise flexible base materials and liquid metal embedded in the base materials; the middle dielectric layer is arranged between the upper electrode layer and the lower electrode layer, is made of the same flexible base material as the upper electrode layer and the lower electrode layer, and has a multi-layer stepped mesoporous microstructure on the middle surface;
when the sensor is stressed by pressure, tension or is approached by a conductor, the capacitance between the upper electrode layer and the lower electrode layer changes, and the magnitude of the pressure, the tension or the distance between the conductor and the sensor, which is stressed by the sensor, is obtained by measuring the change of the capacitance of the sensor.
When the sensor is stressed by pressure, tension or is close to a conductor, the multilayer stepped mesoporous microstructure of the middle dielectric layer controls the thickness change rate under compression through a layered structure, and the linearity of the sensor is improved; the compressibility of the middle dielectric layer is improved through pores in the mesoporous structure, and the sensitivity of the sensor is improved.
Further preferably, the distance between the upper and lower electrode layers is preferably 50um to 200um, and the thickness of the upper and lower electrode layers is preferably 100um to 200 um.
Further preferably, the preparation process of the intermediate electrode layer selects a gel injection molding method to centrifugally prepare a multilayer stepped mesoporous microstructure, and flexible base materials identical to the upper electrode layer and the lower electrode layer are used as dielectric layer materials.
Further preferably, the thickness of the intermediate dielectric layer is preferably 100um to 200 um.
Further preferably, the flexible matrix material is preferably PDMS, ecoflex, PI, PTFE or PET.
Further preferably, the liquid metal is preferably a gallium alloy.
According to another aspect of the present invention, there is provided a method for preparing the above-mentioned flexible sensor, the method comprising the steps of:
(a) preparing upper and lower electrode layers
(a1) Selecting a substrate and a sacrificial layer solution, spin-coating the sacrificial layer solution on the substrate, forming a sacrificial layer on the matrix after the sacrificial layer solution is solidified, spin-coating the solution of the flexible matrix material on the sacrificial layer, forming a flexible matrix layer on the sacrificial layer after the solidification,
(a2) attaching a mask plate to the flexible substrate layer, sputtering an adhesion layer on the mask plate, filling liquid metal in the adhesion layer, and removing the mask plate, wherein the adhesion layer is used for bonding the flexible substrate layer and the liquid metal;
(a3) spin-coating the solution of the flexible matrix layer on the flexible matrix layer sputtered with the liquid metal again, embedding the liquid metal in the flexible matrix layer after solidification, putting the substrate into water, and dissolving the sacrificial layer in the water to separate the flexible matrix layer from the substrate so as to obtain an upper electrode or a lower electrode;
(b) preparing an intermediate dielectric layer
(b1) Mixing polydimethylsiloxane and deionized water, adjusting the mass ratio of the deionized water to the polydimethylsiloxane to generate different pores, and then stirring the mixture for a period of time;
(b2) the well-stirred suspension is poured into a centrifugal tube, the centrifugal tube is centrifuged by a centrifuge, the centrifugal force is kept parallel to the length of the centrifugal tube, the deionized water is guaranteed to form mesopores with different sizes in the moving process, and the multilayer stepped mesoporous film produced from the centrifugal tube has a stepped mesoporous structure with different sizes along the gravity direction. After a layered structure is formed, drying the suspension to remove deionized water, and then stripping the polydimethylsiloxane film from the surface of the centrifugal tube to obtain an intermediate dielectric layer with a multi-layer stepped mesoporous microstructure;
(c) and bonding the upper electrode layer, the middle dielectric layer and the lower electrode layer together in sequence from top to bottom by adopting a reactive ion etching mode, thereby obtaining the required flexible sensor.
Further preferably, in the step (a2), the adhesion layer preferably includes an upper layer and a lower layer, the lower layer is gold, and the upper layer is chromium, wherein the gold is used for connecting the flexible base material and the chromium, and the chromium is used for connecting the gold and the flexible base material.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
1. compared with a sensor without the middle dielectric layer, the middle dielectric layer arranged on the sensor provided by the invention has higher sensitivity in a high-pressure stage (67.5 kPa-140 kPa); the medium-pressure stage (12 kPa-67.5 kPa) shows better linearity; the sensitivity of the low-pressure stage (0 kPa-12 kPa) is obviously improved; the integral linearity is obviously improved;
2. the flexible sensor provided by the invention can measure two parameters of pressure and space positioning distance, is based on a capacitance sensing principle, and can realize real-time monitoring and feedback of the whole process from positioning to grabbing of a robot when being applied to the field of robots;
3. the flexible sensor provided by the invention is tightly attached to the surface of an object to be measured and can keep common contact, so that the gap between the sensor and the surface of the robot is reduced to the maximum extent, and the strength of the sensor and the accuracy of measurement are improved.
Drawings
FIG. 1 is a flow chart of the preparation of a flexible capacitive sensor electrode layer constructed in accordance with a preferred embodiment of the invention;
FIG. 2 is a flow chart of the fabrication of an interlayer dielectric layer of a flexible capacitive sensor constructed in accordance with a preferred embodiment of the present invention;
fig. 3 is a flow chart of the packaging of a flexible capacitive sensor constructed in accordance with a preferred embodiment of the invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-silicon wafer, 2-sacrificial layer, 3-solidified polydimethylsiloxane film, 4-chromium, 5-gold, 6-ultraviolet light, 7-mask, 8-photoresist, 9-etching solution of gold, 10-etching solution of chromium, 11-acetone, 12-isopropanol, 13-polydimethylsiloxane film with liquid metal electrode, 14-liquid metal, 15-crystallizing dish with deionized water, 16-small amount of deionized water, 17-polydimethylsiloxane, and 18-polydimethylsiloxane film with multilayer stepped mesoporous microstructure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 3, the flexible sensor based on the multifunctional sensing principle has a three-layer structure, which can be divided into an upper electrode layer, a middle dielectric layer and a lower electrode layer, wherein the upper and lower electrodes are made of liquid metal materials, so that the tensile property of the electrode layers is improved; the intermediate dielectric layer adopts a multilayer stepped mesoporous microstructure, the elastic modulus is reduced along with the increase of the porosity of the multilayer stepped mesoporous film, the rigidity of a dielectric material is effectively reduced, the intermediate dielectric is easier to deform under the same load, the sensitivity of the sensor for pressure sensing based on a capacitance sensing principle is enhanced, and a layered stepped mesoporous structure is formed as the diameter of a stepped hole is reduced along the vertical direction, so that the thickness change rate under compression is effectively controlled, and the linearity of a capacitance change curve is improved.
The upper electrode substrate, the lower electrode substrate and the middle dielectric layer are made of flexible and stretchable high polymer materials such as PDMS, ecoflex, PI, PTFE or PET and serve as a supporting layer and a dielectric layer of the sensor. The material has good stretchability to ensure the effectiveness of the electrode in working in a stretchable state, and simultaneously has a higher relative dielectric constant as a dielectric layer, thereby ensuring a larger initial capacitance value of the sensor. The functional layers of the upper electrode and the lower electrode are used for collecting and transmitting voltage and capacitance signals, and a liquid metal material is adopted, and comprises the following components in percentage by mass: 68.5 percent of gallium, 21.5 percent of indium and 10 percent of tin, and the material has good conductive performance and tensile property. The upper electrode layer, the middle dielectric layer and the lower electrode layer of the sensor are made of stretchable materials, so that the sensor has good stretchable performance. By adjusting the process parameters, the overall thickness of the sensor can be reduced so that the sensor can be closely attached to the robot surface by van der waals forces and maintain good conformal contact.
In order to improve the success rate and the quality of the sensor, the preparation method of the flexible capacitive sensor with high sensitivity mainly comprises a multilayer stepped mesoporous microstructure process, an electrode process, a sacrificial layer process and a reactive ion etching process. The multilayer stepped mesoporous microstructure technology is used for preparing a middle dielectric layer, the electrode technology is used for preparing an upper electrode layer and a lower electrode layer, the sacrificial layer technology is used for releasing the sensor from a silicon wafer 1, and the reactive ion etching technology is used for bonding and packaging the upper electrode layer, the middle dielectric layer and the lower electrode layer. The multilayer stepped mesoporous microstructure technology adopts a centrifugal method to prepare a multilayer ordered microstructure with gradually increased pore diameters on polydimethylsiloxane. The electrode process directly injects liquid metal on the gold electrode pattern by utilizing the hydrophobicity of the liquid metal to polydimethylsiloxane and the hydrophilicity to gold, and the process method simplifies the experimental steps. The sacrificial layer process adopts polyvinyl alcohol as a material, which is an organic high polymer material dissolved in water, is colorless, transparent, nontoxic and harmless, and has good film forming property. The solvent for dissolving the polyvinyl alcohol sacrificial layer is water, so that the silicon wafer 1 and the sensor cannot be damaged, and the environment cannot be polluted. The reactive ion etching process can well bond the upper electrode layer, the middle dielectric layer and the lower electrode layer, and has high packaging strength. The method comprises the following steps:
first, upper and lower electrodes are prepared, wherein the steps (5) to (10) are photolithography
(1) Washing a clean 2-inch silicon wafer 1 by using acetone 11, isopropanol 12 and deionized water in sequence, and then drying by using nitrogen;
(2) spin-coating a sacrificial layer solution, namely a 10% polyvinyl alcohol aqueous solution, on the polished surface of the silicon wafer 1 at a spin-coating speed of 500-800 rpm for 30-60 seconds, then placing the silicon wafer 1 on a hot plate for heating at 80-100 ℃ for 5-15 minutes to evaporate water by heating, and curing the polyvinyl alcohol into a film to form a sacrificial layer 2;
(3) spin-coating polydimethylsiloxane on the silicon wafer 1 coated with the sacrificial layer 2 to serve as an underlayer 3 at a spin-coating speed of 800-1200 rpm for 50-100 s, then placing the silicon wafer 1 on a hot plate to be heated at a heating temperature of 80-100 ℃ for 10-30 min, and curing the polydimethylsiloxane to form a film so as to form a cured polydimethylsiloxane film 3;
(4) putting the silicon wafer 1 in a magnetron cavity to sputter a layer of chromium 4 and gold 5, wherein the thickness of the chromium 4 sputtered is 10-40 nm, the thickness of the gold 5 sputtered is 50-250 nm, and the chromium serves as an adhesion layer between the gold and the polydimethylsiloxane 3;
(5) spin-coating a photoresist 8 (positive photoresist) on the sputtered gold thin film, and adopting multi-step spin-coating, wherein the spin-coating speed is 500-1000 rpm, and the spin-coating time is 5-10 s; then, the spin coating speed is 1000-2500 rpm, the spin coating time is 45-80 s, and the photoresist 8 with the thickness of about 2-4 um is obtained;
(6) prebaking, volatilizing most of solvent in the photoresist, and heating the silicon wafer 1 coated with the photoresist 8 on a hot plate at 50-80 ℃ for 40-100 s;
(7) ultraviolet exposure, namely performing ultraviolet exposure under ultraviolet rays 6 under a prepared pattern of a mask plate 7 by adopting a contact type exposure technology, wherein the photoetching power is 10-20 mW/m2Setting the exposure time to be 5-10 s;
(8) developing for about 15-25 s in a special developing solution for the AZ5214 photoresist, cleaning floating glue on the surface of the gold film by using absolute ethyl alcohol, drying by using nitrogen, observing whether the electrode pattern is developed cleanly under a microscope with a super depth of field, and continuing developing until the photoresist is completely removed from the surface of the gold film if the photoresist remains;
(9) preparing a gold etching solution 9 and a chromium etching solution 10, wherein the adopted gold etching solution 9 is KI and I2Preparing etching solution 9 of gold by potassium iodide, iodine and deionized water according to the mass ratio of 6.64:1.77:60 (1.66: 0.44:60, 3.32:0.89:60 and 8.3:2.22: 60); preparing a chromium etching solution 10, and preparing the chromium etching solution 10 from ammonium ceric nitrate, glacial acetic acid and deionized water according to the proportion of 4g:1mL:20 mL;
(10) wet etching, namely soaking the silicon wafer sputtered with gold 5 and chromium 4 in gold etching solution 9 for 60-120 s, then washing the etching solution on the surface of the silicon wafer with deionized water, and drying the silicon wafer with nitrogen; then, placing the silicon wafer in a chromium etching solution 10, wherein the etching time is 30-50 s, then washing the etching solution on the surface of the silicon wafer, and drying the silicon wafer by using nitrogen to obtain a required gold electrode pattern;
(11) filling liquid metal 14 on the electrode pattern sputtered with gold 5 by using an injector in an oxygen-free glove box, wherein the thickness of the filled liquid metal 14 is 20-50 um, and sucking away redundant liquid metal by using the injector;
(12) spin coating polydimethylsiloxane again on the silicon wafer 1 subjected to the steps at the spin coating speed of 800-1000 rpm for 50-100 s, then placing the silicon wafer on a hot plate for heating at the heating temperature of 80-100 ℃ for 10-30 min, solidifying the polydimethylsiloxane into a film 2 with the thickness of 50-200 um, then placing the silicon wafer into a crystallizing dish 15 filled with deionized water for water bath heating, dissolving the polyvinyl alcohol sacrificial layer 2, and forming a polydimethylsiloxane film 13 with a liquid metal electrode to finish the preparation of the electrode layer;
fig. 2 is a flow chart for preparing an intermediate dielectric layer, constructed in accordance with a preferred embodiment of the present invention, as shown in fig. 2.
(13) Taking 2 clean 20ml centrifuge tubes of the centrifuge tube, pouring 8 ml-12 ml of polydimethylsiloxane 17 with the same volume, adding 200 ul-500 ul of deionized water 16 by using a liquid transfer device, and stirring the mixture for 20-30 minutes to generate uniformly mixed polydimethylsiloxane/deionized water suspension;
(14) putting a centrifugal tube filled with polydimethylsiloxane/deionized water suspension into a symmetrical horizontal rotor centrifugal machine, checking whether a rotor and a cavity are clean, screwing a rotor cover, setting the centrifugal temperature to be 25 ℃ and the centrifugal force to be 3000-4000 g, screwing the rotor cover, and starting centrifugation, wherein the centrifugation time is 40-60 minutes;
(15) after centrifugation, putting the centrifuged centrifugal tube into an oven, heating at 90 ℃ for 15-20 minutes to remove deionized water and form a gap in polydimethylsiloxane;
(16) stripping the polydimethylsiloxane film 18 with the multilayer stepped mesoporous microstructure from the centrifugal tube to complete the preparation of the polydimethylsiloxane film with the multilayer stepped mesoporous microstructure;
finally, the upper and lower electrode layers, the friction layer and the middle dielectric layer are packaged
(17) Adhering an upper electrode layer, a polydimethylsiloxane membrane 18 with a multilayer stepped mesoporous microstructure and a lower electrode layer together by reactive ion etching, then heating the upper electrode layer, the polydimethylsiloxane membrane and the lower electrode layer on a hot plate at the heating temperature of 80-100 ℃ for 20-30 minutes to accelerate the bonding and bonding process, wherein the reactive ion etching parameters are as follows: the flow rate of oxygen is 20 ml/min, the pressure in the reaction chamber is 70 Pa, the radio frequency power is 90W, and the reaction time is 90 seconds, thus completing the preparation of the sensor.
Preferably, the electrode material adopts gallium alloy, and the mass fractions of gallium, indium and tin are respectively 68.5%, 21.5% and 10%.
As optimization, the filling of the liquid metal is carried out in a glove box with the oxygen content less than or equal to 10 ppm.
As optimization, the upper electrode and the lower electrode are manufactured by AZ5214 photoresist, and the thickness of the photoresist is controlled to be 2 +/-0.5 microns.
As an optimization, the intermediate dielectric layer multi-layer stepped mesoporous microstructure is prepared by a centrifugal processing technology, as described in steps (13) - (16), firstly, polydimethylsiloxane and deionized water are mixed, the mass ratio of the deionized water to the polydimethylsiloxane is adjusted to obtain different pores, then the mixture is stirred, then the mixture is poured into a centrifuge tube, the centrifuge tube is centrifuged by a horizontal rotor centrifuge, then heating is carried out, and finally, the polydimethylsiloxane membrane 18 with the multi-layer stepped mesoporous microstructure is peeled off from the centrifuge tube, so that the intermediate dielectric layer is prepared.
As optimization, before the polydimethylsiloxane film is subjected to hydrophobic treatment, the polydimethylsiloxane film and oxygen are subjected to reactive ion etching.
As optimization, the distance between the upper electrode layer and the lower electrode layer is preferably 50um ~ 200um, and the thickness of upper electrode layer and lower electrode layer is preferably 100um ~ 200um, and the distance and the thickness of upper electrode layer and lower electrode layer are used for guaranteeing great electric capacity, promote sensor interference killing feature, and the thickness of middle dielectric layer is preferably 100um ~ 200um to this reduces the middle dielectric layer rigidity of sensor, promotes sensor sensitivity, guarantees sensor stability simultaneously.
Preferably, the flexible matrix material is PDMS, ecoflex, PI, PTFE or PET, so as to ensure the stretchability of the sensor.
The liquid metal is preferably gallium alloy, so as to ensure that the electrode is liquid at normal temperature, ensure the stretchability of the sensor, and simultaneously have no toxicity and are relatively safe
The present invention will be further illustrated with reference to specific examples.
Example 1:
first, upper and lower electrodes are prepared, wherein steps (5) to (10) are photolithography techniques.
(1) Cleaning the polished surface of the 2-inch silicon wafer 1 by using acetone 11, isopropanol 12 and deionized water in sequence, and then drying by using nitrogen;
(2) spin-coating 10% polyvinyl alcohol aqueous solution on the polished surface of the silicon wafer 1 at a spin-coating speed of 500 rpm for 60 seconds, then placing the silicon wafer 1 on a hot plate and heating at 80 ℃ for 15 minutes, and curing the polyvinyl alcohol to form a film to form a sacrificial layer 2;
(3) spin-coating polydimethylsiloxane on the silicon wafer 1 coated with the sacrificial layer at the spin-coating speed of 1000 rpm for 60 seconds, then placing the silicon wafer 1 on a hot plate to be heated at the heating temperature of 90 ℃ for 20 minutes, and curing the polydimethylsiloxane into a film to form a cured polydimethylsiloxane film 3;
(4) putting the silicon wafer 1 coated with the polydimethylsiloxane and the sacrificial layer in a magnetron cavity to sputter a layer of chromium 4 and gold 5, wherein the thickness of the chromium 4 sputtered is 10nm, the thickness of the gold 5 sputtered is 100nm, and the chromium serves as an adhesion layer between the gold and the polydimethylsiloxane;
(5) spin-coating AZ5214 photoresist 8 (positive photoresist) on the sputtered gold thin film, and adopting multi-step spin-coating, wherein the spin-coating speed is 500 r/min, and the spin-coating time is 8 s; then, the spin coating speed is 2500 rpm, the spin coating time is 45s, and the photoresist with the thickness of 2um is obtained;
(6) pre-baking, namely heating the silicon wafer coated with the AZ5214 photoresist 8 on a hot plate at the temperature of 60 ℃ for 60 s;
(7) ultraviolet exposure, namely performing ultraviolet 6 exposure under a prepared mask 7 pattern, wherein a contact exposure technology is adopted, the photoetching power is 15mW/m2, and the exposure time is set to be 7 s;
(8) developing to obtain a required pattern, developing for 20s in a special developing solution for AZ5214 photoresist, cleaning floating glue on the surface of the gold 5 film by using absolute ethyl alcohol, and blow-drying by using nitrogen to completely remove the photoresist from the surface of the gold 5 film;
(9) preparing a gold etching solution 9 and a chromium etching solution 10, wherein the adopted gold etching solution 9 is KI and I2Preparing etching solution 9 of gold from potassium iodide, iodine and deionized water according to the mass ratio of 6.64:1.77: 60; preparing a chromium etching solution 10, and preparing the chromium etching solution 10 from ammonium ceric nitrate, glacial acetic acid and deionized water according to the proportion of 4g:1mL:20 mL;
(10) wet etching to remove gold and chromium outside the photoresist pattern, firstly soaking the silicon wafer sputtered with gold and chromium in gold etching solution for 75s, then washing the silicon wafer surface etching solution with deionized water, and drying with nitrogen; then, the silicon wafer is placed in a chromium etching solution, the etching time is 30s, then the etching solution on the surface of the silicon wafer is washed clean, and the silicon wafer is dried by nitrogen to obtain a required gold electrode pattern;
(11) filling liquid metal 14 on the electrode pattern sputtered with gold by using an injector in an oxygen-free glove box, and sucking away redundant liquid metal by using the injector, wherein the thickness of the liquid metal 14 is about 40 micrometers;
(12) spin coating polydimethylsiloxane again on the silicon wafer 1 subjected to the steps, wherein the spin coating speed is 1000 rpm, and the spin coating time is 60 seconds, then placing the silicon wafer 1 on a hot plate to be heated, the heating temperature is 90 ℃, the heating time is 20 minutes, and the polydimethylsiloxane is cured into a film, wherein the film thickness obtained under the conditions is 100 micrometers;
second, an intermediate dielectric is prepared
(13) Taking 2 clean 20ml centrifuge tubes with centrifuge tubes, pouring 8ml polydimethylsiloxane 17, adding 200ul deionized water 16 by using a pipette, and stirring the mixture for 20 minutes to generate uniformly mixed polydimethylsiloxane/deionized water suspension;
(14) putting the centrifugal tube filled with the polydimethylsiloxane/deionized water suspension into a symmetrical horizontal rotor centrifugal machine, checking whether a rotor and a cavity are clean, screwing a rotor cover, setting the centrifugal temperature to be 25 ℃ and the centrifugal force to be 3000g, screwing the rotor cover, and starting centrifugation, wherein the centrifugation time is 40 minutes;
(15) after the centrifugation is finished, putting the centrifuged centrifugal tube into an oven, heating the centrifugal tube at 90 ℃ for 15 minutes to remove deionized water and form a gap in polydimethylsiloxane;
(16) stripping the polydimethylsiloxane film 18 with the multilayer stepped mesoporous microstructure from the centrifugal tube to complete the preparation of the polydimethylsiloxane film with the multilayer stepped mesoporous microstructure;
finally, the upper and lower electrode layers, the friction layer and the middle dielectric layer are packaged
(17) Adhering the upper electrode layer, the polydimethylsiloxane film 18 with the multilayer stepped mesopores and the lower electrode layer together by reactive ion etching, and then heating the mixture on a hot plate at the heating temperature of 80 ℃ for 30 minutes, wherein the reactive ion etching parameters are as follows: the oxygen flow is 20 ml/min, the pressure in the reaction chamber is 70 Pa, the radio frequency power is 90W, and the reaction time is 90 seconds; and accelerating the bonding and adhering process to finish the preparation of the sensor.
Example 2:
first, upper and lower electrodes are prepared, wherein steps (5) to (10) are photolithography techniques.
(1) Cleaning the polished surface of the 2-inch silicon wafer 1 by using acetone 11, isopropanol 12 and deionized water in sequence, and then drying by using nitrogen;
(2) spin-coating a 10% polyvinyl alcohol aqueous solution on the polished surface of the silicon wafer 1 at a spin-coating speed of 600 rpm for 50 seconds, then placing the silicon wafer 1 on a hot plate and heating at a heating temperature of 80 ℃ for 12 minutes to solidify the polyvinyl alcohol into a film, and forming a sacrificial layer 2;
(3) spin-coating polydimethylsiloxane on the silicon wafer 1 coated with the sacrificial layer at the speed of 900 rpm for 70 seconds, then placing the silicon wafer 1 on a hot plate for heating at the temperature of 80 ℃ for 25 minutes, and curing the polydimethylsiloxane into a film to form a cured polydimethylsiloxane film 3;
(4) putting the silicon wafer 1 coated with the polydimethylsiloxane and the sacrificial layer in a magnetron cavity, and sputtering a layer of chromium 4 and 5-gold, wherein the thickness of the chromium 4 is 20nm in a sputtering mode, the thickness of the gold 5 is 150nm in a sputtering mode, and the chromium 4 serves as an adhesion layer between the gold 5 and the polydimethylsiloxane;
(5) spin-coating AZ5214 photoresist 8 (positive photoresist) on the sputtered gold thin film, and adopting multi-step spin-coating, wherein the spin-coating speed is 800 r/min, and the spin-coating time is 5 s; then spin-coating speed is 2000 rpm, spin-coating time is 60s, and photoresist 8 with thickness of about 3um is obtained;
(6) prebaking, namely putting the silicon wafer coated with the AZ5214 photoresist 8 on a hot plate for heating at 70 ℃ for 50 seconds;
(7) ultraviolet exposure, which is ultraviolet 6 exposure under a prepared pattern of a reticle 7, herein used is a contact exposure technique, wherein the photolithography power is 20mW/m2, and the exposure time is set to 5 s;
(8) developing to obtain a required pattern, developing for 20s in a special developing solution for AZ5214 photoresist, cleaning floating glue on the surface of the gold film by absolute ethyl alcohol, and blow-drying by nitrogen to completely remove the photoresist from the surface of the gold film;
(9) preparing gold etching liquid 9 and chromium etching liquid 10, wherein the adopted gold etching liquid is KI and I2Preparing etching solution 9 of gold from potassium iodide, iodine and deionized water according to the mass ratio of 1.66:0.44: 60; preparing a chromium etching solution 10, and preparing the chromium etching solution from ammonium ceric nitrate, glacial acetic acid and deionized water according to the proportion of 4g:1mL:20 mL;
(10) wet etching to remove gold and chromium outside the photoresist pattern, firstly soaking the silicon wafer sputtered with gold and chromium in a gold etching solution for 90 seconds, then washing the silicon wafer surface etching solution with deionized water, and drying with nitrogen; then, the silicon wafer is placed in a chromium etching solution, the etching time is 35 seconds, then the etching solution on the surface of the silicon wafer is washed clean, and the silicon wafer is dried by nitrogen to obtain a required gold electrode pattern;
(11) filling the liquid metal 14 on the electrode pattern sputtered with gold by using an injector in an oxygen-free glove box, and sucking away the redundant liquid metal 14 by using the injector, wherein the thickness of the liquid metal is about 30 micrometers;
(12) spin coating polydimethylsiloxane again on the silicon wafer 1 subjected to the steps at the spin coating speed of 900 rpm for 70 seconds, then placing the silicon wafer 1 on a hot plate for heating at the heating temperature of 80 ℃ for 25 minutes, and curing the polydimethylsiloxane into a film, wherein the thickness of the obtained film is 120 micrometers;
second, an intermediate dielectric is prepared
(13) Taking 2 clean 20ml centrifuge tubes with centrifuge tubes, pouring 8ml polydimethylsiloxane, adding 300ul deionized water by using a pipette, and stirring the mixture for 25 minutes to generate uniformly mixed polydimethylsiloxane/deionized water suspension;
(14) putting the centrifugal tube filled with the polydimethylsiloxane/deionized water suspension into a symmetrical horizontal rotor centrifugal machine, checking whether a rotor and a cavity are clean, screwing a rotor cover, setting the centrifugal temperature to be 25 ℃ and the centrifugal force to be 3000g, screwing the rotor cover, and starting centrifugation, wherein the centrifugation time is 45 minutes;
(15) after the centrifugation is finished, putting the centrifuged centrifugal tube into an oven, heating the centrifugal tube at 90 ℃ for 20 minutes to remove deionized water and form a gap in polydimethylsiloxane;
(16) stripping the polydimethylsiloxane film 18 with the multilayer stepped mesoporous microstructure from the centrifugal tube to complete the preparation of the polydimethylsiloxane film with the multilayer stepped mesoporous microstructure;
finally, the upper and lower electrode layers, the friction layer and the middle dielectric layer are packaged
(17) Adhering the upper electrode layer, the polydimethylsiloxane film 18 with the multilayer stepped mesopores and the lower electrode layer together by reactive ion etching, and then heating the mixture on a hot plate at the heating temperature of 100 ℃ for 20 minutes, wherein the reactive ion etching parameters are as follows: the oxygen flow is 20 ml/min, the pressure in the reaction chamber is 70 Pa, the radio frequency power is 90W, and the reaction time is 90 seconds; and accelerating the bonding and adhering process to finish the preparation of the sensor.
Example 3:
first, upper and lower electrodes are prepared, wherein steps (5) to (10) are photolithography techniques.
(1) Cleaning the polished surface of the 2-inch silicon wafer 1 by using acetone 11, isopropanol 12 and deionized water in sequence, and then drying by using nitrogen;
(2) spin-coating a 10% polyvinyl alcohol aqueous solution on the polished surface of the silicon wafer 1 at a spin-coating speed of 800 rpm for 40 seconds, then placing the silicon wafer 1 on a hot plate and heating at a heating temperature of 80 ℃ for 15 minutes, and curing the polyvinyl alcohol to form a film to form a sacrificial layer 2;
(3) spin-coating polydimethylsiloxane on the silicon wafer 1 coated with the sacrificial layer at the spin-coating speed of 800 rpm for 80 seconds, then placing the silicon wafer 1 on a hot plate to be heated at the heating temperature of 100 ℃ for 15 minutes, and curing the polydimethylsiloxane into a film to form a cured polydimethylsiloxane film 3;
(4) putting the silicon wafer 1 coated with the polydimethylsiloxane and the sacrificial layer in a magnetron cavity, and sputtering a layer of chromium 4 and gold 5, wherein the thickness of the chromium 4 is sputtered to be 30nm, the thickness of the gold 5 is sputtered to be 50nm, and the chromium 4 serves as an adhesion layer between the gold 5 and the polydimethylsiloxane;
(5) spin-coating AZ5214 photoresist 8 (positive photoresist) on the sputtered gold 4 film, and adopting multi-step spin-coating, wherein the spin-coating speed is 600 revolutions per minute, and the spin-coating time is 7 s; then, the spin coating speed is 1500 rpm, the spin coating time is 70s, and the photoresist 8 with the thickness of 3.5um is obtained;
(6) pre-baking, namely heating the silicon wafer coated with the AZ5214 photoresist 8 on a hot plate for 100s at the temperature of 50 ℃;
(7) ultraviolet exposure, namely performing ultraviolet 6 exposure under a prepared mask 7 pattern, wherein a contact exposure technology is adopted, the photoetching power is 10mW/m2, and the exposure time is set to be 10 s;
(8) developing to obtain a required pattern, developing for 25s in a special developing solution for AZ5214 photoresist, cleaning floating glue on the surface of the gold film by absolute ethyl alcohol, and blow-drying by nitrogen to completely remove the photoresist 8 from the surface of the gold film;
(9) preparing gold etching liquid 9 and chromium etching liquid 10, wherein the adopted gold etching liquid is KI and I2Preparing etching solution 9 of gold from potassium iodide, iodine and deionized water according to the mass ratio of 3.32:0.89: 60; preparing a chromium etching solution 10, and preparing the chromium etching solution 10 from ammonium ceric nitrate, glacial acetic acid and deionized water according to the proportion of 4g:1mL:20 mL;
(10) wet etching, namely removing gold 5 and chromium 4 outside the photoresist pattern, firstly soaking the silicon wafer sputtered with the gold 5 and the chromium 4 in gold etching solution for 60s, then washing the etching solution on the surface of the silicon wafer with deionized water, and drying the silicon wafer with nitrogen; then, the silicon wafer is placed in a chromium etching solution, the etching time is 40s, then the etching solution on the surface of the silicon wafer is washed clean, and the silicon wafer is dried by nitrogen to obtain a required gold electrode pattern;
(11) filling the liquid metal 14 on the electrode pattern sputtered with gold by using an injector in an oxygen-free glove box, and sucking away the redundant liquid metal 14 by using the injector, wherein the thickness of the liquid metal is about 25 micrometers;
(12) spin coating polydimethylsiloxane again on the silicon wafer 1 subjected to the steps, wherein the spin coating speed is 800 revolutions per minute and the spin coating time is 80 seconds, then placing the silicon wafer 1 on a hot plate to be heated, the heating temperature is 100 ℃, the heating time is 15 minutes, and the polydimethylsiloxane is solidified into a film, wherein the film thickness obtained under the conditions is 110 micrometers;
second, an intermediate dielectric is prepared
(13) Taking 2 clean 20ml centrifuge tubes of the centrifuge tube, pouring 10ml polydimethylsiloxane 17, adding 400ul deionized water 16 by using a pipette, and stirring the mixture for 30 minutes to generate uniformly mixed polydimethylsiloxane/deionized water suspension;
(14) putting the centrifugal tube filled with the polydimethylsiloxane/deionized water suspension into a symmetrical horizontal rotor centrifugal machine, checking whether a rotor and a cavity are clean, screwing a rotor cover, setting the centrifugal temperature to be 25 ℃ and the centrifugal force to be 3000g, screwing the rotor cover, and starting centrifugation, wherein the centrifugation time is 40 minutes;
(15) after the centrifugation is finished, putting the centrifuged centrifugal tube into an oven, heating the centrifugal tube at 90 ℃ for 15 minutes to remove deionized water and form a gap in polydimethylsiloxane;
(16) stripping the polydimethylsiloxane film 18 with the multilayer stepped mesoporous microstructure from the centrifugal tube to complete the preparation of the polydimethylsiloxane film with the multilayer stepped mesoporous microstructure;
finally, the upper and lower electrode layers, the friction layer and the middle dielectric layer are packaged
(17) Adhering the upper electrode layer, the polydimethylsiloxane film 18 with the multilayer stepped mesopores and the lower electrode layer together by reactive ion etching, and then heating the mixture on a hot plate at the heating temperature of 80 ℃ for 30 minutes, wherein the reactive ion etching parameters are as follows: the oxygen flow is 20 ml/min, the pressure in the reaction chamber is 70 Pa, the radio frequency power is 90W, and the reaction time is 90 seconds; and accelerating the bonding and adhering process to finish the preparation of the sensor.
Example 4:
first, upper and lower electrodes are prepared, wherein steps (5) to (10) are photolithography techniques.
(1) Cleaning the polished surface of the 2-inch silicon wafer 1 by using acetone 11, isopropanol 12 and deionized water in sequence, and then drying by using nitrogen;
(2) spin-coating a 10% polyvinyl alcohol aqueous solution on the polished surface of the silicon wafer 1 at a spin-coating speed of 700 rpm for 45 seconds, then placing the silicon wafer 1 on a hot plate to be heated at a heating temperature of 90 ℃ for 10 minutes, and curing the polyvinyl alcohol to form a film to form a sacrificial layer 2;
(3) spin-coating polydimethylsiloxane on the silicon wafer 1 coated with the sacrificial layer at the spin-coating speed of 1200 rpm for 50 seconds, then placing the silicon wafer 1 on a hot plate for heating at the heating temperature of 95 ℃ for 18 minutes, and curing the polydimethylsiloxane into a film to form a cured polydimethylsiloxane film 3;
(4) putting the silicon wafer 1 coated with the polydimethylsiloxane and the sacrificial layer in a magnetron cavity, and sputtering a layer of chromium 4 and gold 5, wherein the thickness of the chromium 4 is 40nm in a sputtering mode, the thickness of the gold 5 is 200nm in a sputtering mode, and the chromium 4 serves as an adhesion layer between the gold 5 and the polydimethylsiloxane;
(5) spin-coating AZ5214 photoresist 8 (positive photoresist) on the sputtered gold 4 film, and adopting multi-step spin-coating, wherein the spin-coating speed is 700 r/min, and the spin-coating time is 6 s; then spin-coating at a speed of 1000 rpm for 80s to obtain a photoresist with a thickness of 4 um;
(6) pre-baking, namely heating the silicon wafer coated with the AZ5214 photoresist 8 on a hot plate at the temperature of 80 ℃ for 40 s;
(7) ultraviolet exposure, namely performing ultraviolet 6 exposure under a prepared mask 7 pattern, wherein a contact exposure technology is adopted, the photoetching power is 15mW/m2, and the exposure time is set to be 7 s;
(8) developing to obtain a required pattern, developing for 20s in a special developing solution for AZ5214 photoresist, cleaning floating glue on the surface of the gold thin film 4 by using absolute ethyl alcohol, and blow-drying by using nitrogen to completely remove the photoresist 8 from the surface of the gold thin film 4;
(9) preparing a gold etching solution 9 and a chromium etching solution 10, wherein the adopted gold etching solution 9 is KI and I2Preparing etching solution 9 of gold from potassium iodide, iodine and deionized water according to the mass ratio of 8.3:2.22: 60; preparing a chromium etching solution 10, and preparing the chromium etching solution 10 from ammonium ceric nitrate, glacial acetic acid and deionized water according to the proportion of 4g:1mL:20 mL;
(10) wet etching, namely removing gold 5 and chromium 4 outside the photoresist pattern, firstly soaking the silicon wafer sputtered with the gold 5 and the chromium 4 in gold etching solution 10 for 120s, then washing the etching solution on the surface of the silicon wafer with deionized water, and drying the silicon wafer with nitrogen; then, the silicon wafer is placed in a chromium etching solution 9, the etching time is 50s, then the etching solution on the surface of the silicon wafer is washed clean, and the silicon wafer is dried by nitrogen to obtain a required gold electrode pattern;
(11) filling liquid metal 14 on the electrode pattern sputtered with gold by using an injector in an oxygen-free glove box, and sucking away redundant liquid metal by using the injector, wherein the thickness of the liquid metal 14 is about 20 microns;
(12) spin-coating polydimethylsiloxane again on the silicon wafer 1 subjected to the steps at the spin-coating speed of 1200 rpm for 50 seconds, then placing the silicon wafer 1 on a hot plate for heating at the heating temperature of 95 ℃ for 18 minutes, and curing the polydimethylsiloxane into a film, wherein the thickness of the film obtained under the conditions is 90 micrometers;
second, an intermediate dielectric is prepared
(13) Taking 2 clean 20ml centrifuge tubes of the centrifuge tube, pouring 10ml polydimethylsiloxane 17, adding 500ul deionized water 16 by using a pipette, and stirring the mixture for 30 minutes to generate uniformly mixed polydimethylsiloxane/deionized water suspension;
(14) putting the centrifugal tube filled with the polydimethylsiloxane/deionized water suspension into a symmetrical horizontal rotor centrifugal machine, checking whether a rotor and a cavity are clean, screwing a rotor cover, setting the centrifugal temperature to be 25 ℃ and the centrifugal force to be 4000g, screwing the rotor cover, and starting centrifugation, wherein the centrifugation time is 50 minutes;
(15) after the centrifugation is finished, putting the centrifuged centrifugal tube into an oven, heating the centrifugal tube at 90 ℃ for 20 minutes to remove deionized water and form a gap in polydimethylsiloxane;
(16) stripping the polydimethylsiloxane film 18 with the multilayer stepped mesoporous microstructure from the centrifugal tube to complete the preparation of the polydimethylsiloxane film with the multilayer stepped mesoporous microstructure;
finally, the upper and lower electrode layers, the friction layer and the middle dielectric layer are packaged
(17) Adhering the upper electrode layer, the polydimethylsiloxane film 18 with the multilayer stepped mesopores and the lower electrode layer together by reactive ion etching, and then heating the mixture on a hot plate at the heating temperature of 90 ℃ for 25 minutes, wherein the reactive ion etching parameters are as follows: the oxygen flow is 20 ml/min, the pressure in the reaction chamber is 70 Pa, the radio frequency power is 90W, and the reaction time is 90 seconds; and accelerating the bonding and adhering process to finish the preparation of the sensor.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A polydimethylsiloxane film, characterized in that: the preparation method of the multilayer stepped mesoporous microstructure comprises the following steps:
(b1) stirring and mixing polydimethylsiloxane and deionized water to obtain a suspension;
(b2) and (3) centrifuging the suspension, drying the suspension to remove deionized water after a layered structure is formed, and then stripping the polydimethylsiloxane film.
2. A high-sensitivity flexible capacitive sensor, characterized by: the sensor includes an upper electrode layer, an intermediate dielectric layer, and a lower electrode layer; the upper electrode layer and the lower electrode layer have the same structure and both comprise a flexible base material and liquid metal embedded in the flexible base material; the intermediate dielectric layer is interposed between the upper and lower electrode layers, and the dielectric layer is the polydimethylsiloxane film of claim 1.
3. A high sensitivity flexible capacitive sensor as claimed in claim 2 wherein: the distance between the upper electrode layer and the lower electrode layer is preferably 20um to 250um, the thickness of the upper electrode layer and the lower electrode layer is 50um to 250um, and the thickness of the middle dielectric layer is 20um to 250 um.
4. A high sensitivity flexible capacitive sensor as claimed in claim 2 wherein: the flexible matrix material is preferably PDMS, ecoflex, PI, PTFE or PET.
5. A high sensitivity flexible capacitive sensor as claimed in claim 2 wherein: the liquid metal is gallium indium tin alloy.
6. A method of manufacturing a high sensitivity flexible capacitive sensor according to any one of claims 2 to 5, wherein: the method comprises the following steps:
(a) preparing an upper electrode layer and a lower electrode layer
(a1) Selecting a substrate and a sacrificial layer solution, spin-coating the sacrificial layer solution on the substrate, forming a sacrificial layer on the substrate after the sacrificial layer solution is solidified, spin-coating the solution of the flexible substrate material on the sacrificial layer, and forming a flexible substrate layer on the sacrificial layer after the solution of the flexible substrate material is solidified;
(a2) manufacturing a mask plate on the surface of the flexible substrate layer by adopting a photoetching technology, sputtering an adhesion layer on the mask plate, filling liquid metal on the adhesion layer, and removing the mask plate, wherein the adhesion layer is used for bonding the flexible substrate layer and the liquid metal;
(a3) spin-coating the solution of the flexible matrix layer on the flexible matrix layer filled with the liquid metal again, embedding the liquid metal in the flexible matrix layer after curing, putting the substrate into water, and dissolving the sacrificial layer in the water to separate the flexible matrix layer from the substrate so as to obtain an upper electrode layer and a lower electrode layer respectively;
(b) preparing an intermediate dielectric layer
(b1) Stirring and mixing polydimethylsiloxane and deionized water to obtain a suspension;
(b2) centrifuging the suspension, drying the suspension to remove deionized water after a layered structure is formed, and then stripping the polydimethylsiloxane film;
(c) and bonding the upper electrode layer, the middle dielectric layer and the lower electrode layer together in sequence from top to bottom by adopting a reactive ion etching mode, thereby obtaining the required high-sensitivity flexible capacitive sensor.
7. The method for preparing a high-sensitivity flexible capacitive sensor according to claim 6, wherein: in the step (a2), the adhesion layer preferably includes an upper layer and a lower layer, the lower layer is chromium with a thickness of 10 nm-40 nm, and the upper layer is gold with a thickness of 50 nm-250 nm, wherein the gold is used for connecting the gallium indium tin alloy and the chromium, and the chromium is used for connecting the gold and the flexible base material.
8. The method for preparing a high-sensitivity flexible capacitive sensor according to claim 6, wherein: the sacrificial layer solution is polyvinyl alcohol solution.
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| CN113091811A (en) * | 2021-03-31 | 2021-07-09 | 电子科技大学 | Flexible temperature and pressure integrated sensor and preparation method and application thereof |
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| CN113670487B (en) * | 2021-07-14 | 2022-07-19 | 西南交通大学 | A kind of composite flexible piezoresistive sensor based on bionic multilevel structure and preparation method thereof |
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