阅读说明：本技术 一种灵敏度可调的柔性压力传感器及其制备方法和应用 (Flexible pressure sensor with adjustable sensitivity and preparation method and application thereof ) 是由 应义斌 彭博 平建峰 于 2021-06-24 设计创作，主要内容包括：本发明公开了一种灵敏度可调的柔性压力传感器及其制备方法和应用。方法包括以下步骤：制备得到碳化钛纳米片分散液；将海绵浸泡在碳化钛纳米片分散液中,并真空干燥,得到第一状态的导电海绵；将第一状态的导电海绵浸入硝酸银溶液中,并真空干燥,得到第二状态的导电海绵；利用激光诱导技术在聚酰亚胺薄膜上制备叉指电极；将第二状态的导电海绵粘贴在叉指电极上,使导电海绵与叉指电极接触,然后将导线连接于叉指电极的两端,得到灵敏度可调的柔性压力传感器。本发明制备的柔性压力传感器成本较低,制备过程简单,且灵敏度可调,能适应不同场合检测的需求。(The invention discloses a flexible pressure sensor with adjustable sensitivity and a preparation method and application thereof. The method comprises the following steps: preparing titanium carbide nanosheet dispersion liquid; soaking sponge in titanium carbide nanosheet dispersion liquid, and drying in vacuum to obtain conductive sponge in a first state; immersing the conductive sponge in the first state into a silver nitrate solution, and performing vacuum drying to obtain the conductive sponge in the second state; preparing an interdigital electrode on a polyimide film by using a laser induction technology; and pasting the conductive sponge in the second state on the interdigital electrode to enable the conductive sponge to be in contact with the interdigital electrode, and then connecting the lead to two ends of the interdigital electrode to obtain the flexible pressure sensor with adjustable sensitivity. The flexible pressure sensor prepared by the invention has the advantages of low cost, simple preparation process and adjustable sensitivity, and can meet the detection requirements of different occasions.)

1. A preparation method of a flexible pressure sensor with adjustable sensitivity is characterized by comprising the following steps:

step S1: dispersing titanium carbide nanosheets in water to prepare titanium carbide nanosheet dispersion liquid;

step S2: soaking the sponge into the titanium carbide nanosheet dispersion liquid obtained in the step S1, and then performing vacuum drying to obtain a conductive sponge in a first state;

step S3: soaking the conductive sponge in the first state obtained in the step S2 in a silver nitrate solution, and then drying in vacuum to obtain the conductive sponge in the second state;

step S4: etching an interdigital electrode on the polyimide film by using a laser induction method;

step S5: and (4) attaching the conductive sponge in the second state obtained in the step (S3) to the interdigital electrode obtained in the step (S4), so that the conductive sponge is in contact with the interdigital electrode, and then connecting wires to two ends of the interdigital electrode, so as to prepare the flexible pressure sensor with adjustable sensitivity.

2. The method for preparing the adjustable-sensitivity flexible pressure sensor according to claim 1, wherein the method comprises the following steps: in step S1, a liquid phase stripping method is adopted to strip and obtain a titanium carbide nanosheet dispersion liquid, wherein the concentration of the titanium carbide nanosheet dispersion liquid is 4 mg/mL.

3. The method for preparing the adjustable-sensitivity flexible pressure sensor according to claim 1, wherein the method comprises the following steps: step S2 specifically includes: soaking the sponge into the titanium carbide nanosheet dispersion liquid, standing for 1-6 h at the temperature of 4 ℃, and then vacuum-drying for 60min at the temperature of 60 ℃ to obtain the conductive sponge in the first state.

4. The method for preparing the adjustable-sensitivity flexible pressure sensor according to claim 1, wherein the method comprises the following steps: in step S3, the concentration of silver nitrate solution is 0.5-5 mmol/L, the vacuum drying time is 90min, and the temperature is 60 ℃.

5. The method for preparing the adjustable-sensitivity flexible pressure sensor according to claim 1, wherein the method comprises the following steps: in step S3, the soaking time of the conductive sponge in the first state in the silver nitrate solution is 1-5S.

6. The method for preparing the adjustable-sensitivity flexible pressure sensor according to claim 1, wherein the method comprises the following steps: in step S4, the thickness of the polyimide film is 130 μm, the laser power is 4W during laser induction, and the etching speed is 3 cm/S.

7. The utility model provides a sensitivity adjustable flexible pressure sensor which characterized in that: the preparation method is characterized by being prepared by the preparation method of any one of claims 1 to 5.

8. Use of the adjustable sensitivity flexible pressure sensor of claim 1, wherein: the application in monitoring human joint movement, pulse and crop fruit growth.

Technical Field

The invention relates to the technical field of biosensors, in particular to a flexible pressure sensor with adjustable sensitivity and a preparation method and application thereof.

Background

In recent years, flexible pressure sensors are widely applied to the fields of human joint movement, soft robots and the like. The flexible pressure sensor mainly comprises three types, namely a piezoresistive type, a piezoelectric type and a pressure-capacitance type. Under the action of the external pressure, the electrical property of the active functional material changes, so that the output of the electrical signal (resistance, capacitance or voltage) of the sensor changes. And establishing a linear relation between the output of the electric signal and the external pressure, and measuring the external pressure. The substrate material of the early flexible pressure sensor is mostly Polydimethylsiloxane (PDMS), Polyimide (PI) and other polymers, and the active functional material and the conductive material are transferred to the surface of the substrate material by various methods to form a planar structure. In recent years, higher requirements have been placed on the structure and material of the flexible pressure sensor for high detection accuracy and high sensitivity detection.

Among the numerous structures, flexible pressure sensors of three-dimensional porous structure have been extensively studied in recent years. Compared with the traditional structure, the three-dimensional porous structure has relatively lower compression modulus, so that the three-dimensional porous structure obtains larger deformation under lower external pressure. In the piezoresistive sensor, the surface of the material of the three-dimensional porous structure is decorated with a conductive material to impart conductivity. When it is compressed, the conductive materials come into contact with each other, so that the number of conductive paths increases and the resistance of the sensor decreases. The common methods for preparing the sensor with the three-dimensional porous structure mainly comprise a freeze-drying and high-temperature annealing method, a template method and the like. The methods are complicated and time-consuming to operate, and the performance of the obtained sensor cannot meet the requirements of various test occasions. Therefore, it is necessary to develop a flexible pressure sensor with simple manufacturing steps and diversified performances.

Disclosure of Invention

Aiming at the characteristics that the existing flexible pressure sensor is complex in preparation process and can only meet the single detection requirement, the invention provides the flexible pressure sensor with the adjustable sensitivity of the sponge structure.

The invention provides the following technical scheme:

preparation method of flexible pressure sensor with adjustable sensitivity

The method comprises the following steps:

step S1: dispersing titanium carbide (Ti3C2) nanosheets in water to prepare a titanium carbide nanosheet dispersion liquid;

step S1, the specific method is as follows:

(1-1) to 10mL of 9mol/L concentrated hydrochloric acid was added 0.8g of LiF to obtain a LiF/HCl mixed solution. Subsequently, 0.5g of Ti was slowly added to the mixed solution₃AlC₂The powder was stirred at 50 ℃ for 48 h.

(1-2) the above solution was washed several times with deionized water until the solution pH was > 6. Then, the mixture was centrifuged at 3500r/min for 3min to obtain a precipitate.

(1-3) adding a proper amount of deionized water into the precipitate, and carrying out ultrasonic treatment for 1 hour in an ice bath. And centrifuging at 8000r/min for 1h, taking supernatant to obtain titanium carbide nanosheet dispersion, and adjusting the concentration to 4 mg/mL.

Step S2: soaking the sponge into the titanium carbide nanosheet dispersion liquid obtained in the step S1, and then performing vacuum drying to obtain a conductive sponge in a first state;

step S3: soaking the conductive sponge in the first state obtained in the step S2 in a silver nitrate solution, and then drying in vacuum to obtain the conductive sponge in the second state;

step S4: etching an interdigital electrode on the polyimide film by using a laser induction method;

step S5: and (4) attaching the conductive sponge in the second state obtained in the step (S3) to the interdigital electrode obtained in the step (S4), so that the conductive sponge is in contact with the interdigital electrode, and then connecting wires to two ends of the interdigital electrode, so as to prepare the flexible pressure sensor with adjustable sensitivity.

In step S1, a liquid phase stripping method is adopted to strip and obtain a titanium carbide nanosheet dispersion liquid, wherein the concentration of the titanium carbide nanosheet dispersion liquid is 4 mg/mL.

Step S2 specifically includes: soaking sponge with the size of 10 multiplied by 2mm into the titanium carbide nanosheet dispersion liquid, standing for 1-6 h at the temperature of 4 ℃, and then vacuum-drying for 60min at the temperature of 60 ℃ to obtain the conductive sponge in the first state.

In step S2, titanium carbide nanosheets are adsorbed onto the surface of the sponge. When the soaking time is too short, the conductivity is poor, and when the soaking time reaches a certain value, the adsorption amount of the titanium carbide reaches saturation, and at the moment, the conductivity of the conductive sponge in the first state reaches stability.

In step S3, the concentration of silver nitrate solution is 0.5-5 mmol/L, the vacuum drying time is 90min, and the temperature is 60 ℃.

In step S3, the soaking time of the conductive sponge in the first state in the silver nitrate solution is 1-5S. The conductive sponge in the first state is soaked in the silver nitrate solution for different time periods to generate different numbers of silver nanoparticles, so that the sensors with different sensitivities are obtained.

In step S3, after the conductive sponge in the first state is immersed in a silver nitrate solution, the titanium carbide nanosheets reduce silver ions in the solution into silver nanoparticles. The generation amount of the silver nanoparticles can be controlled by controlling the concentration of the silver nitrate solution and the soaking time.

The concentration of the silver nitrate solution in the step S3 is 1 mmol/L; further preferably, when the joint movement of the human body is monitored, the soaking time is 1 s. When the human body pulse is monitored, the soaking time is 3 s. When tomato fruit growth was monitored, the soaking time was 1 s.

In step S4, the thickness of the polyimide film is 130 μm, the laser power is 4W during laser induction, and the etching speed is 3 cm/S.

Application of flexible pressure sensor with adjustable sensitivity

The application in monitoring human joint movement, pulse and crop fruit growth.

In the invention, when the titanium carbide nanosheets are adsorbed on the surface of the sponge, the sponge is endowed with conductivity. When the sponge is compressed under certain external pressure, the titanium carbide nano sheets contact with each other, so that the conductive path is increased. In the process, more conductive paths are formed between the conductive sponge and the interdigital electrodes, so that the resistance is reduced. When the external force continues to increase, the number of the conductive paths does not increase any more, the stability is maintained, and the resistance does not decrease any more. When the conductive sponge in the first state is soaked in a silver nitrate solution, the reduction performance of the titanium carbide nanosheets enables silver ions in the solution to be reduced into silver nanoparticles which are distributed on the surface of the conductive sponge, and therefore the roughness of the surface of the conductive sponge is increased. Under the action of smaller external force, the contact between the silver nano particles can form more conductive paths, so that the sensitivity of the sensor is improved. The greater the number of silver nanoparticles, the higher the sensitivity. The invention utilizes the property to construct the flexible pressure sensor with different sensitivities by adjusting the roughness of the conductive sponge by the silver nano-particles, thereby realizing the monitoring of different application scenes such as human joint movement, pulse, fruit growth and the like.

The action principle of the flexible pressure sensor is as follows: when the conductive sponge in the first state is soaked in a silver nitrate solution, the reduction performance of the titanium carbide nanosheets enables silver ions in the solution to be reduced into silver nanoparticles which are distributed on the surface of the conductive sponge, and therefore the roughness of the surface of the conductive sponge is increased. Under the action of smaller external force, the contact between the silver nano particles can form more conductive paths, so that the sensitivity of the sensor is improved. The greater the number of silver nanoparticles, the higher the sensitivity. The relative rate of change of resistance is linear with ambient pressure. The magnitude of the ambient pressure can be calculated from the relative rate of change of resistance.

The invention has the beneficial effects that:

the invention utilizes the property to construct the flexible pressure sensor with different sensitivities, which can monitor different application scenes such as human joint movement, pulse, fruit growth and the like, and the flexible pressure sensor prepared by the invention has the advantages of lower cost for monitoring the indexes, simple preparation process and adjustable sensitivity, and can meet the detection requirements of different occasions.

Drawings

FIG. 1 is a graph of resistance after sponge soaking as a function of soaking time;

FIG. 2 is a graph of the rate of change of resistance versus pressure for a flexible pressure sensor made from a second state of conductive sponge (different silver nitrate solution concentrations);

FIG. 3 is a graph showing the variation of resistance rate with pressure of a flexible pressure sensor made of a second state of conductive sponge (different soaking times in silver nitrate solution)

FIG. 4 is a graph of the rate of change of resistance of a flexible pressure sensor made from a second state of conductive sponge to monitor knee flexion;

FIG. 5 is a graph of the rate of change of resistance of a flexible pressure sensor made of a second state of conductive sponge when monitoring pulse;

FIG. 6 is a graph of the rate of change of resistance of a flexible pressure sensor made from a second state of conductive sponge as it monitors the growth of tomato fruit.

Detailed Description

The invention will be described in further detail below with reference to the drawings and examples, which are intended to facilitate the understanding of the invention without limiting it in any way.

Example 1

Step S1: the titanium carbide nanosheet dispersion is prepared by stripping with a liquid phase stripping method, and the specific method is as follows:

1) to 10mL of 9mol/L concentrated hydrochloric acid was added 0.8g of lithium fluoride (LiF) to obtain a lithium fluoride/hydrochloric acid (LiF/HCl) mixed solution, and subsequently, to the lithium fluoride/hydrochloric acid mixed solution was slowly added 0.5g of titanium aluminum carbide (Ti)₃AlC₂) The powder was stirred at 50 ℃ for 48 h.

2) The above solution was washed several times with deionized water until the solution pH >6, followed by centrifugation at 3500r/min for 3min and the pellet taken.

3) Adding a proper amount of deionized water into the precipitate, carrying out ultrasonic treatment for 1 hour in an ice bath, centrifuging for 1 hour at 8000r/min, taking supernatant to obtain titanium carbide nanosheet dispersion, and adjusting the concentration to 4 mg/mL.

Step S2: soaking sponge with the size of 10mm multiplied by 2mm into the titanium carbide nanosheet dispersion liquid, taking out after soaking for different time at the temperature of 4 ℃, then carrying out vacuum drying in a vacuum drying oven with the temperature of 60 ℃ for 60min, obtaining the conductive sponge in the first state after drying, taking out the conductive sponge in the first state from the vacuum drying oven, and measuring the resistance between two points on the diagonal line of the sponge. The resistances of the conductive sponges with soaking times of 1, 2, 3, 4, 5, and 6h were measured as shown in fig. 1. It can be seen that in the initial stage of soaking, the resistance of the conductive sponge in the first state shows a trend of decreasing with the increase of the soaking time, which indicates that the titanium carbide nanosheets are continuously adsorbed on the surface of the sponge in the process. When the soaking time reaches 4h, the adsorption capacity of the titanium carbide nanosheets reaches saturation, and when the soaking time is longer, the resistance of the conductive sponge reaches a stable state and is not reduced any more. Therefore, the soaking time of the sponge is preferably 4 h.

Step S3: and (4) completely immersing the conductive sponge in the first state prepared in the step S2 into a silver nitrate solution with the concentration of 0.5mmol/L for 3S, taking out, and performing vacuum drying at 60 ℃ for 90min to obtain the conductive sponge in the second state.

Step S4: and etching the interdigital electrode on the polyimide film by using a laser induction method, wherein the thickness of the polyimide film is 130 micrometers, the laser power is 4W, and the etching speed is 3 cm/s.

Step S5: and (4) attaching the conductive sponge in the second state obtained in the step (S3) to the interdigital electrode in the step (S4), so that the conductive sponge is in contact with the interdigital electrode, and then connecting conducting wires to two ends of the interdigital electrode, so as to prepare the flexible pressure sensor with adjustable sensitivity.

Example 2

The procedure of example 2 is the same as that of example 1, except that:

in step S3, the concentration of the silver nitrate solution is 1 mmol/L.

Example 3

The procedure of example 3 is the same as that of example 1, except that:

in step S3, the concentration of the silver nitrate solution is 3 mmol/L.

Example 4

The procedure of example 4 is the same as that of example 1, except that:

in step S3, the concentration of the silver nitrate solution is 5 mmol/L.

The flexible pressure sensors with adjustable sensitivity obtained in the embodiments 1 to 4 are respectively connected with a multimeter, the initial resistance of the flexible pressure sensor with adjustable sensitivity is recorded, a certain pressure is applied to the flexible pressure sensor with adjustable sensitivity, the resistance value of the flexible pressure sensor with adjustable sensitivity is recorded after the pressure is applied, and the resistance change rate is calculated. (the resistance variation is the difference between the resistance of the sensor after applying pressure and the initial resistance, and the ratio of the resistance variation to the initial resistance is the resistance variation rate), drawing a standard curve of the resistance variation rate changing with the external pressure, and obtaining the sensitivity of the sensor. The conductive sponge in the first state is soaked in silver nitrate solution, so that silver nanoparticles are generated on the surface of the conductive sponge. The different concentrations of silver nitrate solutions produce different quantities of silver nanoparticles, and the different sensitivities of the resulting sensors. As a result, as shown in fig. 2, the sensor sensitivity showed a tendency to increase as the concentration of the silver nitrate solution increased. Meanwhile, the linear range of the detection of the sensor gradually decreases along with the increase of the concentration of the silver nitrate solution. The two indexes of sensitivity and linear range are integrated, and the concentration of the selected silver nitrate solution is 1 mmol/L.

Example 5

Step S1: the titanium carbide nanosheet dispersion is prepared by stripping with a liquid phase stripping method, and the specific method is as follows:

1) to 10mL of 9mol/L concentrated hydrochloric acid was added 0.8g of lithium fluoride (LiF) to obtain a lithium fluoride/hydrochloric acid (LiF/HCl) mixed solution, and subsequently, to the lithium fluoride/hydrochloric acid mixed solution was slowly added 0.5g of titanium aluminum carbide (Ti)₃AlC₂) The powder was stirred at 50 ℃ for 48 h.

2) The above solution was washed several times with deionized water until the solution pH >6, followed by centrifugation at 3500r/min for 3min and the pellet taken.

3) Adding a proper amount of deionized water into the precipitate, carrying out ultrasonic treatment for 1 hour in an ice bath, centrifuging for 1 hour at 8000r/min, taking supernatant to obtain titanium carbide nanosheet dispersion, and adjusting the concentration to 4 mg/mL.

Step S2: soaking sponge with the size of 10mm multiplied by 2mm into the titanium carbide nanosheet dispersion liquid at the temperature of 4 ℃ for 4 hours, taking out, then carrying out vacuum drying in a vacuum drying oven at the temperature of 60 ℃ for 60 minutes, and drying to obtain the conductive sponge in the first state.

Step S3: and (4) completely soaking the conductive sponge in the first state prepared in the step (S2) into a silver nitrate solution with the concentration of 1mmol/L for 1S, taking out, and performing vacuum drying at 60 ℃ for 90min to obtain the conductive sponge in the second state.

Step S4: and etching the interdigital electrode on the polyimide film by using a laser induction method, wherein the thickness of the polyimide film is 130 micrometers, the laser power is 4W, and the etching speed is 3 cm/s.

Step S5: and (4) attaching the conductive sponge in the second state obtained in the step (S3) to the interdigital electrode in the step (S4), so that the conductive sponge is in contact with the interdigital electrode, and then connecting conducting wires to two ends of the interdigital electrode, so as to prepare the flexible pressure sensor with adjustable sensitivity.

Example 6

The procedure of example 6 is the same as that of example 5, except that:

in step S3, the soaking time was 3 seconds.

Example 7

The procedure of example 7 is the same as that of example 5, except that:

in step S3, the soaking time is 5 seconds.

The flexible pressure sensors with adjustable sensitivity prepared in the embodiments 5 to 7 are respectively connected with a multimeter, the initial resistance of the flexible pressure sensor with adjustable sensitivity is recorded, a certain pressure is applied to the flexible pressure sensor with adjustable sensitivity, the resistance value of the flexible pressure sensor with adjustable sensitivity is recorded after the pressure is applied, the resistance change rate is calculated, and a curve of the resistance change rate changing along with the external pressure is drawn, so that the sensitivity of the flexible pressure sensor with adjustable sensitivity can be obtained. The soaking time in the silver nitrate solution can also affect the amount of silver nanoparticles produced, which in turn affects the sensitivity of the sensor. The results are shown in FIG. 3. In this example, the longer the soaking time of the conductive sponge in the first state in the silver nitrate solution, the higher the sensitivity of the resulting sensor, but the narrower the linear range. According to the time length of soaking in the silver nitrate solution, the sensors with different sensitivities are obtained, and therefore the function of adjusting the sensitivity is achieved.

Application of the flexible pressure sensor with adjustable sensitivity:

1) application to knee joint

The flexible sensor with adjustable sensitivity prepared in example 5 is pasted at the knee joint, a universal meter is connected to enable the knee to bend or straighten freely, the resistance change of the knee during free bending and straightening is recorded, and a curve of the resistance change rate changing with time is drawn.

The results are shown in FIG. 4. When the knee is bent, the joint part generates certain pressure on the sensor, so that the resistance of the sensor is reduced. When the knee is extended, the pressure disappears and the sensor resistance returns to the initial resistance.

2) Application to wrist pulse beating

The flexible sensor with adjustable sensitivity prepared in the embodiment 6 is pasted at the wrist pulse jumping position, a universal meter is connected, the resistance change is recorded, and a curve of the resistance change rate changing along with time is drawn.

The pulsation of the pulse gives the sensor some pressure, so that the sensor resistance decreases. The results are shown in FIG. 5. Note that, in order to fit the resistance change rate curve to the pulse waveform, the ordinate in fig. 5 is the inverse of the resistance change rate.

3) Application on tomato fruit surface

The flexible sensor with adjustable sensitivity prepared in example 5 is adhered to the surface of a tomato fruit, a universal meter is connected, the resistance change is recorded, and a curve of the resistance change rate changing along with time is drawn.

The results are shown in FIG. 6. Fruit swelling puts some pressure on the sensor, causing the sensor resistance to decrease. Thereby reflecting the growth state of the fruit.

The above-mentioned embodiments are intended to illustrate the technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, additions, equivalents, etc. made within the scope of the principles of the present invention should be included in the scope of the present invention.