阅读说明：本技术 柔性压力传感器及其制备方法、可穿戴设备 (Flexible pressure sensor, preparation method thereof and wearable device ) 是由 刘静 李文博 李静 王佳伟 李炯利 王旭东 罗圭纳 王刚 于 2021-11-15 设计创作，主要内容包括：本发明涉及传感器技术领域,具体而言,涉及一种柔性压力传感器及其制备方法、可穿戴设备。柔性压力传感器包括叉指电极层、压感层及位于叉指电极层与压感层之间的粘附层；叉指电极层相邻叉指间的距离有任意一种关系：(a)由叉指电极层中心向外,相邻叉指间的距离从0.2mm～0.6mm逐渐增大至0.6mm～1.2mm；(b)由叉指电极层中心向外,相邻叉指间的距离从0.6mm～1.2mm逐渐减小至0.2mm～0.6mm；压感层中石墨烯的质量百分含量为0.6%～2%,粘附层的中部留空将叉指电极层与压感层的边缘部位粘接以使叉指电极层与压感层之间形成气腔,粘附层还有缺口以使气腔与外界连通。传感器检测灵敏度较高。(The invention relates to the technical field of sensors, in particular to a flexible pressure sensor, a preparation method of the flexible pressure sensor and wearable equipment. The flexible pressure sensor comprises an interdigital electrode layer, a pressure sensing layer and an adhesion layer positioned between the interdigital electrode layer and the pressure sensing layer; the distance between adjacent interdigital electrodes of the interdigital electrode layer has any relation: (a) the distance between adjacent interdigital electrodes gradually increases from 0.2 mm-0.6 mm to 0.6 mm-1.2 mm from the center of the interdigital electrode layer to the outside; (b) the distance between adjacent interdigital electrodes is gradually reduced from 0.6 mm-1.2 mm to 0.2 mm-0.6 mm from the center of the interdigital electrode layer to the outside; the mass percentage of graphene in the pressure-sensitive layer is 0.6% -2%, the middle part of the adhesion layer is reserved with a space to bond the interdigital electrode layer and the edge part of the pressure-sensitive layer so as to form an air cavity between the interdigital electrode layer and the pressure-sensitive layer, and the adhesion layer is also provided with a notch so as to communicate the air cavity with the outside. The sensor has high detection sensitivity.)

1. The flexible pressure sensor is characterized by comprising an interdigital electrode layer, a pressure sensing layer and an adhesion layer positioned between the interdigital electrode layer and the pressure sensing layer;

the distance between adjacent interdigital electrodes in the interdigital electrode layer has any one of the following relations:

(a) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is gradually increased from 0.2 mm-0.6 mm to 0.6 mm-1.2 mm;

(b) the distance between adjacent interdigital electrodes is gradually reduced from 0.6 mm-1.2 mm to 0.2 mm-0.6 mm from the center of the interdigital electrode layer to the outside;

the mass percentage of graphene in the pressure-sensitive layer is 0.6% -2%, the middle of the adhesion layer is left empty, the interdigital electrode layer is bonded with the edge part of the pressure-sensitive layer so that an air cavity is formed between the interdigital electrode layer and the pressure-sensitive layer, and the adhesion layer is also provided with a notch so that the air cavity is communicated with the outside.

2. The flexible pressure sensor of claim 1 wherein the distance between adjacent interdigitated fingers in said interdigitated electrode layer has any of the following relationships:

(a) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is 0.2 mm-0.6 mm firstly and then 0.6 mm-1.2 mm, and the logarithm ratio of interdigital electrode pairs is (1-5): 1-5);

(b) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is 0.6 mm-1.2 mm firstly and then 0.2 mm-0.6 mm, and the logarithm ratio of the interdigital electrode pair is (1-5): 1-5).

3. The flexible pressure sensor according to claim 1, wherein the interdigital electrode layer has a thickness of 0.02mm to 0.2mm, the pressure-sensitive layer has a thickness of 0.04mm to 0.5mm, and the adhesive layer has a thickness of 0.02mm to 0.1 mm.

4. The flexible pressure sensor according to claim 1, wherein the mass percentage of graphene in the interdigital electrode layer is 2.5% -5%.

5. The flexible pressure sensor according to any one of claims 1 to 4, wherein the adhesive layer is a double-sided tape or a hot-melt adhesive film.

6. The flexible pressure sensor according to any one of claims 1 to 4, wherein the interdigital electrode layer and the pressure sensing layer are both circular, the adhesion layer is a notched ring, and the arc length of the notch of the adhesion layer is 1mm to 3 mm.

7. A method of manufacturing a flexible pressure sensor according to any of claims 1 to 6, comprising the steps of:

forming an interdigital electrode with a preset structure on a first flexible substrate by using the graphene composite slurry, and drying to prepare an interdigital electrode layer;

coating a sensing raw material containing graphene on a second flexible substrate and drying to prepare a pressure sensing layer; and

and adhering the interdigital electrode layer and the edge of the pressure-sensitive layer by using an adhesive layer with a gap.

8. The method for preparing the flexible pressure sensor according to claim 7, wherein the sensing raw materials further comprise 5-25% by mass of vinyl chloride-vinyl acetate copolymer, 0.5-5% by mass of silica aerogel and a first organic solvent.

9. The method for preparing the flexible pressure sensor according to claim 7, wherein the graphene composite slurry further comprises a vinyl chloride-vinyl acetate copolymer and a second organic solvent besides the graphene, and the vinyl chloride-vinyl acetate copolymer is 5-25% by mass.

10. The method of any one of claims 7 to 9, wherein the first flexible substrate and the second flexible substrate are independently selected from a PET film, a PI film, or a PDMS film.

11. A wearable device comprising the flexible pressure sensor of any of claims 1-6.

Technical Field

The invention relates to the technical field of sensors, in particular to a flexible pressure sensor, a preparation method of the flexible pressure sensor and wearable equipment.

Background

The flexible sensor has the characteristics of good flexibility, free bending, even folding, convenience in carrying and the like, and can adapt to a more complex application scene. Has wide application prospect in the fields of health management, medical treatment, sports science and the like. At present, researchers mostly adopt sensing mechanisms such as resistance type, capacitance type, piezoelectric type, and triboelectric type to prepare pressure sensors with high sensitivity. Among them, the resistive sensor is widely noticed by researchers due to the advantages of simple preparation process, easy signal reading, high sensitivity, fast response time, low cost, and the like. Most of traditional flexible piezoresistive sensors are formed by taking a polymer substrate with a micro-nano structure as a surface conductive coating or compounding conductive filler into a polymer frame, so that the change of a conductive path under different pressures is realized, and the output of an electric signal is achieved. However, the design and processing of the micro-nano structure increase the preparation process and the manufacturing cost of the sensor, and meanwhile, the technology mainly aims at improving the sensitivity under micro deformation and limits the detection range of the sensor. The sensor which compounds the conductive filler into the polymer (such as rubber and the like) matrix to be used as the pressure sensing layer is generally suitable for detecting larger deformation, and has limited detection range and low sensitivity, thereby limiting the application range of the sensor. Meanwhile, due to the viscoelasticity and creep behavior of the polymer, the response time of the sensor has a lag problem, and after a large acting force is applied, the recovery time of the sensor is long, the initial resistance value cannot be recovered, and the sensor has slow response time and poor stability.

Disclosure of Invention

Based on the above, the invention provides a flexible pressure sensor capable of improving detection sensitivity and widening detection range, a preparation method thereof and wearable equipment.

In one aspect of the invention, a flexible pressure sensor is provided, which comprises an interdigital electrode layer, a pressure-sensitive layer and an adhesion layer located between the interdigital electrode layer and the pressure-sensitive layer;

the distance between adjacent interdigital electrodes in the interdigital electrode layer has any one of the following relations:

(a) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is gradually increased from 0.2 mm-0.6 mm to 0.6 mm-1.2 mm;

(b) the distance between adjacent interdigital electrodes is gradually reduced from 0.6 mm-1.2 mm to 0.2 mm-0.6 mm from the center of the interdigital electrode layer to the outside;

the mass percentage of graphene in the pressure-sensitive layer is 0.6% -2%, the middle of the adhesion layer is left empty, the interdigital electrode layer is bonded with the edge part of the pressure-sensitive layer so that an air cavity is formed between the interdigital electrode layer and the pressure-sensitive layer, and the adhesion layer is also provided with a notch so that the air cavity is communicated with the outside.

Optionally, in the flexible pressure sensor as described above, the distance between adjacent interdigital electrodes in the interdigital electrode layer has any one of the following relationships:

(a) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is 0.2 mm-0.6 mm firstly and then 0.6 mm-1.2 mm, and the logarithm ratio of interdigital electrode pairs is (1-5): 1-5);

(b) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is 0.6 mm-1.2 mm firstly and then 0.2 mm-0.6 mm, and the logarithm ratio of the interdigital electrode pair is (1-5): 1-5).

Optionally, as for the flexible pressure sensor, the thickness of the interdigital electrode layer is 0.02 mm-0.2 mm, the thickness of the pressure sensing layer is 0.04 mm-0.5 mm, and the thickness of the adhesion layer is 0.02 mm-0.1 mm.

Optionally, in the flexible pressure sensor, the mass percentage of the graphene in the interdigital electrode layer is 2.5% -5%.

Optionally, as for the flexible pressure sensor, the adhesive layer is a double-sided tape or a hot-melt adhesive film.

Optionally, as for the flexible pressure sensor, the interdigital electrode layer and the pressure sensing layer are both circular, the adhesion layer is a notched ring, and the arc length of the notch of the adhesion layer is 1 mm-3 mm.

The invention also provides a preparation method of the flexible pressure sensor, which comprises the following steps:

forming an interdigital electrode with a preset structure on a first flexible substrate by using the graphene composite slurry, and drying to prepare an interdigital electrode layer;

coating a sensing raw material containing graphene on a second flexible substrate and drying to prepare a pressure sensing layer; and

and adhering the interdigital electrode layer and the edge of the pressure-sensitive layer by using an adhesive layer with a gap.

Optionally, in the preparation method of the flexible pressure sensor, the sensing raw materials further include, by mass, 5% to 25% of vinyl chloride-vinyl acetate copolymer, and 0.5% to 5% of silica aerogel, and a first organic solvent.

Optionally, in the preparation method of the flexible pressure sensor, the graphene composite slurry further includes, in addition to graphene, a vinyl chloride-vinyl acetate copolymer and a second organic solvent, and the vinyl chloride-vinyl acetate copolymer is 5% to 25% by mass.

Optionally, in the method for manufacturing a flexible pressure sensor, the first flexible substrate and the second flexible substrate are independently selected from a PET film, a PI film, or a PDMS film.

In another aspect of the present invention, there is further provided a wearable device including the flexible pressure sensor described above.

The flexible pressure sensor provided by the invention has the advantages that:

(1) the detection range of the sensor can be regulated and controlled by regulating the content of graphene in the pressure-sensitive layer (namely the resistance value of the pressure-sensitive layer) and the distance between adjacent interdigital electrodes in the interdigital electrode layer, and the sensor has high sensitivity in a wider detection range.

(2) The interdigital electrode layer and the pressure-sensitive layer can be integrally assembled through the adhesion layer, so that the subsequent packaging process is omitted, the operation process is simplified, and the cost is reduced. And the existence of the adhesion layer can enable an air cavity to be formed between the interdigital electrode layer and the pressure sensing layer, and the gap of the adhesion layer is convenient for the discharge and filling of air in the air cavity. The interdigital electrode layer and the pressure sensing layer can be quickly separated by timely filling of gas, so that the recovery time of the flexible pressure sensor is shortened, and the stability and repeatability of the flexible pressure sensor are ensured.

(3) The method avoids the use of a polymer substrate with a microstructure, and has the characteristics of high response speed, short recovery time, good stability, easy regulation and control of a detection range and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 (a) is a schematic structural diagram of the interdigital electrode layer prepared in example 1, (b) is a schematic structural diagram of the pressure-sensitive layer, and (c) is a schematic structural diagram of the adhesion layer;

FIG. 2 is a graph showing the results of a sensitivity test of the flexible pressure sensor manufactured in example 1 under a stress of 50g to 200g, and (b) showing the results of a sensitivity test of the flexible pressure sensor under a stress of 1kg to 4 kg;

FIG. 3 is a schematic structural view of an interdigital electrode layer obtained in example 2;

FIG. 4 (a) is a graph showing the results of the sensitivity test of the flexible pressure sensor manufactured in example 2 under a stress of 30g to 200g, and (b) is a graph showing the results of the sensitivity test of the flexible pressure sensor under a stress of 1kg to 4 kg;

FIG. 5 is a schematic structural view of an interdigital electrode layer obtained in example 3;

FIG. 6 is a graph showing the resistance of the flexible pressure sensor manufactured in example 3 as a function of force;

FIG. 7 is a graph showing the results of a sensitivity test of the flexible pressure sensor manufactured in example 3 under a stress of 50g to 200g, and (b) showing the results of a sensitivity test of the flexible pressure sensor under a stress of 1kg to 4 kg;

FIG. 8 is a graph showing the response of the flexible pressure sensor made in example 3 to a pressure signal;

FIG. 9 is a graph showing the results of a cycle performance test of the flexible pressure sensor manufactured in example 3;

FIG. 10 is an enlarged view of the area A in FIG. 9;

FIG. 11 is a graph showing the resistance of the flexible pressure sensor manufactured in example 4 as a function of force;

FIG. 12 is a graph of resistance versus force for the flexible pressure sensor made in example 5;

fig. 13 is a graph showing the resistance value of the flexible pressure sensor manufactured in comparative example 1 as a function of the force.

Detailed Description

Reference will now be made in detail to embodiments of the invention, one or more examples of which are described below. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment.

It is therefore intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present invention are disclosed in or are apparent from the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

The invention provides a flexible pressure sensor, which comprises an interdigital electrode layer, a pressure sensing layer and an adhesion layer positioned between the interdigital electrode layer and the pressure sensing layer;

wherein, the distance between adjacent interdigital in the interdigital electrode layer has any one of the following relations:

(a) the distance between adjacent interdigital electrodes gradually increases from 0.2 mm-0.6 mm to 0.6 mm-1.2 mm from the center of the interdigital electrode layer to the outside;

(b) the distance between adjacent interdigital electrodes is gradually reduced from 0.6 mm-1.2 mm to 0.2 mm-0.6 mm from the center of the interdigital electrode layer to the outside;

the mass percentage of graphene in the pressure-sensitive layer is 0.6% -2%, the middle of the adhesion layer is left empty, the interdigital electrode layer and the edge part of the pressure-sensitive layer are bonded to form an air cavity between the interdigital electrode layer and the pressure-sensitive layer, and the adhesion layer is further provided with a notch so that the air cavity is communicated with the outside.

The detection range of the sensor can be regulated and controlled by regulating the distance between adjacent interdigital electrodes in the interdigital electrode layer or the content of graphene in the pressure-sensitive layer (namely the resistance value of the pressure-sensitive layer), and the sensor has high sensitivity in a wider detection range. In addition, the interdigital electrode layer and the pressure-sensitive layer can be integrally assembled through the adhesion layer, so that the subsequent packaging process is omitted, the operation process is simplified, and the cost is reduced. And the existence of the adhesion layer can enable an air cavity to be formed between the interdigital electrode layer and the pressure sensing layer, and the gap of the adhesion layer is convenient for the discharge and filling of air in the air cavity. The interdigital electrode layer and the pressure sensing layer can be quickly separated by timely filling of gas, so that the recovery time of the flexible pressure sensor is shortened, and the stability and repeatability of the flexible pressure sensor are ensured. And the use of a polymer substrate with a microstructure is avoided, and the method has the characteristics of high response speed, short recovery time, good stability, easy regulation and control of a detection range and the like.

In some embodiments, the distance between adjacent fingers in the interdigitated electrode layer has any of the following relationships:

(a) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is 0.2 mm-0.6 mm firstly and then 0.6 mm-1.2 mm, and the logarithmic ratio of the interdigital electrode pair is (1-5): 1-5);

(b) from the center of the interdigital electrode layer to the outside, the distance between adjacent interdigital electrodes is 0.6 mm-1.2 mm firstly and then 0.2 mm-0.6 mm, and the logarithm ratio of the interdigital electrode pair is (1-5): 1-5).

In some embodiments, the pair ratio of the interdigitated electrode pairs may also be independently 1:2, 1:3, 1:4, 2:1, 2:2, 2:3, 2:4, 2:5, 3:1, 3:2, 3:3, 3:4, 3:5, 4:1, 4:2, 4:3, 4:4, 4:5, 5:2, 5:3, 5:4, and the like.

In some embodiments, the thickness of the interdigital electrode layer, the pressure-sensitive layer and the adhesion layer can be any thickness, for example, the thickness of the interdigital electrode layer is 0.02mm to 0.2mm, the thickness of the pressure-sensitive layer is 0.04mm to 0.5mm, and the thickness of the adhesion layer is 0.02mm to 0.1 mm.

In some embodiments, the width of the fingers in the interdigital electrode layer is not limited too much, and may be 0.2mm to 0.5 mm.

In some embodiments, the mass percentage of graphene in the interdigital electrode layer is 2.5% to 5%.

In some embodiments, the adhesive layer may be a double-sided tape or a hot melt adhesive film. The kind of the double-sided tape can be any known double-sided tape, including but not limited to a mesh double-sided tape, a reinforced double-sided tape, a Rubber double-sided tape, a high-temperature double-sided tape, a non-woven double-sided tape, a non-adhesive double-sided tape, a tissue double-sided tape, a double-sided glass cloth tape, a PET double-sided tape, a foam double-sided tape, and the like. The hot melt adhesive film can be EVA hot melt adhesive.

In some embodiments, the shapes of the interdigital electrode layer and the pressure-sensitive layer can be designed according to practical application scenarios, for example, the shapes can be circular or regular polygons, wherein the regular polygons can be squares, rectangles, pentagons, hexagons, etc., and the adhesion layer is a ring with a notch, and the shape of the ring is the same as the shape of the interdigital electrode layer and the pressure-sensitive layer. In a specific embodiment, the interdigital electrode layer and the pressure-sensitive layer are both circular, the adhesion layer is a notched ring, and the arc length of a notch of the adhesion layer is 1 mm-3 mm. The arc length of the notch is limited within the range, so that excellent adhesion between the interdigital electrode layer and the pressure-sensitive layer can be ensured, and good filling and discharging of air between the interdigital electrode layer and the pressure-sensitive layer can be ensured.

The invention also provides a preparation method of the flexible pressure sensor, which comprises the following steps:

forming an interdigital electrode with a preset structure on a first flexible substrate by using the graphene composite slurry, and drying to prepare an interdigital electrode layer;

coating a sensing raw material containing graphene on a second flexible substrate and drying to prepare a pressure sensing layer; and

and sticking the interdigital electrode layer and the edge of the pressure-sensitive layer by using an adhesive layer with a gap.

In some embodiments, the specific steps of preparing the interdigitated electrode layer include: printing or printing the graphene composite paste on a first flexible substrate to form an interdigital electrode with a preset structure, and drying. The printing may be ink-direct-write printing, and the printing may be screen printing.

In some embodiments, the method of coating may be screen printing, blade coating, direct ink writing printing techniques, and the like.

In some embodiments, the sensing raw material further comprises 5-25% by mass of a vinyl chloride-vinyl acetate copolymer, 0.5-5% by mass of a silica aerogel and a first organic solvent.

In some embodiments, the graphene composite slurry further comprises, in addition to graphene, a vinyl chloride-vinyl acetate copolymer and a second organic solvent, wherein the vinyl chloride-vinyl acetate copolymer is 5-25% by mass.

In some embodiments, the material of the first flexible substrate and the second flexible substrate may be any material known in the art, for example, the first flexible substrate and the second flexible substrate are independently selected from a PET film, a PI film, or a PDMS film.

In some embodiments, it is within the ability of one skilled in the art to select the first organic solvent and the second organic solvent as desired, and may be, for example, a dibasic ester (DBE), Propylene Glycol Methyl Ether Acetate (PGMEA), cyclohexanone (CYC), isophorone 783, ethylene glycol monobutyl ether (BCS), diacetone alcohol (DAA), and the like, and the first organic solvent and the second organic solvent may be the same or different. In order to reduce VOC and ensure safety and health, the first organic solvent and the second organic solvent are dibasic esters.

In another aspect of the present invention, there is further provided a wearable device including the flexible pressure sensor described above. The wearable device is suitable for detection of applied force of a flexible non-planar object, such as detection of finger touch force or detection of plantar pressure distribution.

In some embodiments, the wearable device includes smart footwear, a control glove, a wrist band, a neck band, a watch, and the like.

The flexible pressure sensor, the method for manufacturing the same, and the wearable device according to the present invention will be described in further detail with reference to specific examples and comparative examples.

The trigger force in the following examples is defined as the resistance reachedThe minimum force applied is as follows.

Example 1

1) Preparation of interdigital electrode layer

20g of vinyl chloride-vinyl acetate copolymer is put into 80g of dibasic ester solvent, heated and stirred at 60 ℃ until the vinyl chloride-vinyl acetate copolymer is completely dissolved to form vinyl chloride-vinyl acetate copolymer solution. And then taking 20g of vinyl chloride-vinyl acetate copolymer solution, adding 0.8g of graphene, uniformly dispersing, defoaming in vacuum, and stirring for 10min to obtain the graphene composite slurry. Printing the graphene composite slurry on a PET film by using a screen printing plate to form interdigital electrodes with a preset structure shown in (a) in figure 1, wherein the interdigital width of the interdigital electrode is 0.25mm, the electrode diameter is within 8.5mm, and the distance between adjacent interdigital electrodes is 0.75mm, and the number of pairs is 2; the diameter of the electrodes is 8.5 mm-13.75 mm, the distance between adjacent interdigital electrodes is 0.375mm, and the total number of the interdigital electrodes is 4. Then, placing the PET film containing the interdigital electrode structure in a 95 ℃ oven to heat for 15h to prepare an electrode layer;

2) preparation of pressure-sensitive layers

Weighing 20g of the vinyl chloride-vinyl acetate copolymer solution obtained in the step 1), adding 0.25g of silicon dioxide aerogel and 0.2g of graphene, and carrying out vacuum defoaming and stirring for 10min to obtain a uniformly dispersed sensing raw material. Printing sensing raw materials on a PET film by using a silk screen printing plate, and then drying in an oven at 80 ℃ for 15h to obtain a pressure-sensitive layer shown as (b) in figure 1, wherein the diameter of the pressure-sensitive layer is 17mm, and the measured resistance value of the pressure-sensitive layer is；

3) Preparation of adhesive layer

Cutting the EVA hot melt adhesive film with the thickness of 0.05mm into a circular ring with a notch by adopting a laser cutting technology, wherein the outer diameter of the circular ring is 17mm, the inner diameter of the circular ring is 14.5mm, and the arc length at the notch is 2mm to prepare an adhesive layer shown in (c) in figure 1;

4) preparation of flexible pressure sensor

Adhering the interdigital electrode layer prepared in the step 1) and the edge of the pressure-sensitive layer prepared in the step 2) by using the adhesive layer in the step 3), and then heating and pressing at 100 ℃ to synthesize the flexible pressure sensor.

And (3) carrying out performance test on the prepared flexible pressure sensor:

as shown in fig. 2, when the inter-finger distance of the inter-finger electrodes is sparse first and dense second, the trigger force is 50 g. As shown in FIG. 2 (a), the sensitivity S of the sensor is calculated at a micro stress of 50g to 200g₁Is 4.37kg^-1(ii) a As shown in FIG. 2 (b), the sensitivity S of the sensor is within the range of 1kg to 4kg under a large stress₂Is 0.24kg^-1。

Example 2

This example is prepared substantially identically to example 1, except that: the parameters of the interdigital electrodes are different. The method comprises the following specific steps:

1) preparation of interdigital electrode layer

20g of vinyl chloride-vinyl acetate copolymer is put into 80g of dibasic ester solvent, heated and stirred at 60 ℃ until the vinyl chloride-vinyl acetate copolymer is completely dissolved to form vinyl chloride-vinyl acetate copolymer solution. And then taking 20g of vinyl chloride-vinyl acetate copolymer solution, adding 0.8g of graphene, uniformly dispersing, defoaming in vacuum, and stirring for 10min to obtain the graphene composite slurry. Printing the graphene composite slurry on a PET film by using a silk screen printing plate to form interdigital electrodes with a preset structure as shown in FIG. 3, wherein the interdigital width of the interdigital electrode is 0.25mm, the electrode diameter is within 8.5mm, and the distance between adjacent interdigital electrodes is 0.375mm, and 4 pairs in total; the diameter of each electrode is 8.5 mm-13.75 mm, and the distance between adjacent interdigital electrodes is 0.75mm, so that 2 pairs are formed. Then, placing the PET film containing the interdigital electrode structure in a 95 ℃ oven to heat for 15h to prepare an electrode layer;

2) preparation of pressure-sensitive layers

Weighing 20g of the vinyl chloride-vinyl acetate copolymer solution obtained in the step 1), adding 0.25g of silicon dioxide aerogel and 0.2g of graphene, and carrying out vacuum defoaming and stirring for 10min to obtain a uniformly dispersed sensing raw material. Printing sensing raw materials on a PET (polyethylene terephthalate) film with a diameter by adopting a silk screen printing plate, and then drying the PET film in an oven with the temperature of 80 ℃ for 15 hours to prepare a pressure-sensitive layer, wherein the diameter of the pressure-sensitive layer is 17mm, and the resistance value of the pressure-sensitive layer is measured to be；

3) Preparation of adhesive layer

Cutting an EVA hot melt adhesive film with the thickness of 0.05mm into a circular ring with a notch by adopting a laser cutting technology, wherein the outer diameter of the circular ring is 17mm, the inner diameter of the circular ring is 14.5mm, and the arc length at the notch is 2mm to prepare an adhesive layer;

4) preparation of flexible pressure sensor

Adhering the interdigital electrode layer prepared in the step 1) and the edge of the pressure-sensitive layer prepared in the step 2) by using the adhesive layer in the step 3), and then heating and pressing at 100 ℃ to synthesize the flexible pressure sensor.

And (3) carrying out performance test on the prepared flexible pressure sensor:

as shown in fig. 4, when the inter-finger distance of the inter-finger electrodes is dense first and then sparse, the trigger force is 30 g. As shown in FIG. 4 (a), the sensitivity S of the sensor is calculated at a micro stress of 30g to 200g₃Is 5.25kg^-1(ii) a As shown in FIG. 4 (b), the sensitivity S of the sensor is within the range of 1kg to 4kg under a large stress₄Is 0.17kg^-1。

Example 3

This example is prepared substantially identically to example 1, except that: the parameters of the interdigital electrodes are different. The method comprises the following specific steps:

1) preparation of interdigital electrode layer

20g of vinyl chloride-vinyl acetate copolymer is put into 80g of dibasic ester solvent, heated and stirred at 60 ℃ until the vinyl chloride-vinyl acetate copolymer is completely dissolved to form vinyl chloride-vinyl acetate copolymer solution. And then taking 20g of vinyl chloride-vinyl acetate copolymer solution, adding 0.8g of graphene, uniformly dispersing, defoaming in vacuum, and stirring for 10min to obtain the graphene composite slurry. And printing the graphene composite slurry on the PET film by using a screen printing plate to form the interdigital electrode with a preset structure shown in FIG. 5, wherein the interdigital width of the interdigital electrode is 0.25mm, and the distance between adjacent interdigital electrodes is 0.75mm, and the total number of pairs is 4. Then, placing the PET film containing the interdigital electrode structure in a 95 ℃ oven to heat for 15h to prepare an electrode layer;

2) preparation of pressure-sensitive layers

Weighing 20g of the vinyl chloride-vinyl acetate copolymer solution obtained in the step 1), adding 0.25g of silicon dioxide aerogel and 0.2g of graphene, and carrying out vacuum defoaming and stirring for 10min to obtain a uniformly dispersed sensing raw material. Printing sensing raw materials on a PET film by adopting a screen printing plate, and then drying the PET film in a drying oven at 80 ℃ for 15 hours to prepare a pressure-sensitive layer, wherein the diameter of the pressure-sensitive layer is 17mm, and the resistance value of the pressure-sensitive layer is measured to be；

3) Preparation of adhesive layer

Cutting an EVA hot melt adhesive film with the thickness of 0.05mm into a circular ring with a notch by adopting a laser cutting technology, wherein the outer diameter of the circular ring is 17mm, the inner diameter of the circular ring is 14.5mm, and the arc length at the notch is 2mm to prepare an adhesive layer;

4) preparation of flexible pressure sensor

Adhering the interdigital electrode layer prepared in the step 1) and the edge of the pressure-sensitive layer prepared in the step 2) by using the adhesive layer in the step 3), and then heating and pressing at 100 ℃ to synthesize the flexible pressure sensor.

And (3) carrying out performance test on the prepared flexible pressure sensor:

as can be seen from FIG. 6, when the inter-finger distances of the inter-finger electrodes are the same, the trigger force of the sensor is 50g, and the measurement range is about 0.05kg to 7 kg.

As shown in FIG. 7 (a), the sensitivity S of the sensor is calculated at a minute stress of 50g to 200g₅Is 4.26kg^-1(ii) a As shown in FIG. 7 (b), the sensitivity S of the sensor is within the range of 1kg to 4kg under a large stress₆Is 0.19kg^-1。

As can be seen from the relevant test data of embodiments 1 to 3, the present invention can flexibly adjust and control the performance of the sensor by designing the distance between adjacent interdigital electrodes (i.e., the density of the interdigital electrodes) of the same interdigital electrode. When the resistance values of the pressure-sensitive layers are the same, when the interdigital electrodes which are first sparse and then dense are used, compared with the interdigital electrodes with the same density, the number of the electrodes which are in contact with the pressure-sensitive layers in the sensor under larger stress is increased, the change rate of the resistance values is increased, and the sensitivity under larger stress is improved while the detection sensitivity under small stress is maintained (as shown in fig. 2); when the interdigital electrodes are dense and then sparse, the number of the electrodes contacting with the pressure sensing layer under small stress is increased, the sensitivity is higher, but the resistance value does not change along with the pressure when reaching a certain value (which is caused by the intrinsic piezoresistance of the sensing material), and the method is suitable for detecting the micro stress (as shown in fig. 4). When the interdigital electrodes with the same density are used, the resistance value is rapidly reduced firstly under smaller stress, and then a platform area appears along with the increase of the stress, so that the sensitivity is reduced (as shown in figures 6 and 7).

FIG. 8 is a graph of the response of a flexible pressure sensor to a pressure signal. As can be seen from fig. 8, when a pressure of 1kg is applied to the flexible pressure sensor at a rate of 300mm/s and the pressure is released after 5 seconds, the signal response time is 30.08ms and the recovery time is 29.71 ms. The sensor prepared by the invention has the characteristic of quick response.

Fig. 9 is a graph showing the results of the cycle performance test of the flexible pressure sensor, and fig. 10 is an enlarged view of a portion a in fig. 9. As can be seen from fig. 9 and 10, the flexible pressure sensor manufactured by the present invention has excellent cycle stability.

The reason is that after the notch design is carried out on the adhesion layer, the sensor can be quickly restored to the initial state after the stress is released, and the cycle stability of the sensor is ensured.

Example 4

This example is prepared substantially identically to example 3, except that: the content of graphene in the pressure-sensitive layer is different. The method comprises the following specific steps:

1) preparation of interdigital electrode layer

20g of vinyl chloride-vinyl acetate copolymer is put into 80g of dibasic ester solvent, heated and stirred at 60 ℃ until the vinyl chloride-vinyl acetate copolymer is completely dissolved to form vinyl chloride-vinyl acetate copolymer solution. And then taking 20g of vinyl chloride-vinyl acetate copolymer solution, adding 0.8g of graphene, uniformly dispersing, defoaming in vacuum, and stirring for 10min to obtain the graphene composite slurry. The method comprises the steps of loading graphene composite slurry into a needle cylinder, printing the graphene composite slurry on a PET (polyethylene terephthalate) film by using a needle head with the diameter of 200 mu m under the conditions that the pressure is 20Psi and the linear speed is 6mm/s, and forming the interdigital electrode with a preset structure, wherein the interdigital width of the interdigital electrode is 0.25mm, and the distance between adjacent interdigital electrodes is 0.75mm, and 4 pairs in total. Then, placing the PET film containing the interdigital electrode structure in a 95 ℃ oven to heat for 15h to prepare an electrode layer;

2) preparation of pressure-sensitive layers

Weighing 20g of the vinyl chloride-vinyl acetate copolymer solution obtained in the step 1), adding 0.25g of silicon dioxide aerogel and 0.25g of graphene, and carrying out vacuum defoaming and stirring for 10min to obtain a uniformly dispersed sensing raw material. Printing sensing raw materials on a PET film by adopting a screen printing plate, and then drying the PET film in a drying oven at 80 ℃ for 15 hours to prepare a pressure-sensitive layer, wherein the resistance value of the pressure-sensitive layer is measured to be；

3) Preparation of adhesive layer

Cutting an EVA hot melt adhesive film with the thickness of 0.05mm into a circular ring with a notch by adopting a laser cutting technology, wherein the outer diameter of the circular ring is 17mm, the inner diameter of the circular ring is 14.5mm, and the arc length at the notch is 2mm to prepare an adhesive layer;

4) preparation of flexible pressure sensor

Adhering the interdigital electrode layer prepared in the step 1) and the edge of the pressure-sensitive layer prepared in the step 2) by using the adhesive layer in the step 3), and then heating and pressing at 100 ℃ to synthesize the flexible pressure sensor.

The graph of the resistance value of the manufactured flexible pressure sensor along with the change of the force value is shown in fig. 11. As can be seen from FIG. 11, the trigger force of the sensor is 13g, and the measuring range is about 0.015kg to 5 kg.

Example 5

This example is prepared substantially identically to example 3, except that: the content of graphene in the pressure-sensitive layer is different. The method comprises the following specific steps:

1) preparation of interdigital electrode layer

20g of vinyl chloride-vinyl acetate copolymer is put into 80g of dibasic ester solvent, heated and stirred at 60 ℃ until the vinyl chloride-vinyl acetate copolymer is completely dissolved to form vinyl chloride-vinyl acetate copolymer solution. And then taking 20g of vinyl chloride-vinyl acetate copolymer solution, adding 0.8g of graphene, uniformly dispersing, defoaming in vacuum, and stirring for 10min to obtain the graphene composite slurry. The method comprises the steps of loading graphene composite slurry into a needle cylinder, printing the graphene composite slurry on a PET (polyethylene terephthalate) film by using a needle head with the diameter of 200 mu m under the conditions that the pressure is 20Psi and the linear speed is 6mm/s, and forming the interdigital electrode with a preset structure, wherein the interdigital width of the interdigital electrode is 0.25mm, and the distance between adjacent interdigital electrodes is 0.75mm, and 4 pairs in total. Then, placing the PET film containing the interdigital electrode structure in a 95 ℃ oven to heat for 15h to prepare an electrode layer;

2) preparation of pressure-sensitive layers

Weighing 20g of the vinyl chloride-vinyl acetate copolymer solution obtained in the step 1), adding 0.25g of silicon dioxide aerogel and 0.3g of graphene, and carrying out vacuum defoaming and stirring for 10min to obtain a uniformly dispersed sensing raw material. Printing sensing raw materials on a PET film by adopting a screen printing plate, and then drying the PET film in a drying oven at 80 ℃ for 15 hours to prepare a pressure-sensitive layer, wherein the resistance value of the pressure-sensitive layer is measured to be；

3) Preparation of adhesive layer

Cutting an EVA hot melt adhesive film with the thickness of 0.05mm into a circular ring with a notch by adopting a laser cutting technology, wherein the outer diameter of the circular ring is 17mm, the inner diameter of the circular ring is 14.5mm, and the arc length at the notch is 2mm to prepare an adhesive layer;

4) preparation of flexible pressure sensor

Adhering the interdigital electrode layer prepared in the step 1) and the edge of the pressure-sensitive layer prepared in the step 2) by using the adhesive layer in the step 3), and then heating and pressing at 100 ℃ to synthesize the flexible pressure sensor.

The graph of the resistance value of the manufactured flexible pressure sensor along with the change of the force value is shown in fig. 12. As can be seen from FIG. 12, the trigger force of the sensor is 10g, and the measuring range is about 0.010kg to 2 kg.

From the embodiments 3 to 5, when the interdigital electrode layer with the same density is used, the adjustment and control of the detection range of the sensor can be realized by adjusting the resistance value (graphene content of the pressure-sensitive layer) of the pressure-sensitive layer. That is to say, the invention can realize the regulation and control of the detection range of the sensor and the improvement of the sensitivity by regulating and controlling the density of the interdigital electrode and the resistance value of the pressure sensitive layer.

Comparative example 1

This comparative example was prepared substantially the same as example 3, except that: the graphene content in the pressure-sensitive layer was 0.5 g. Measuring the resistance of the pressure-sensitive layer as. As can be seen from FIG. 13, the trigger force of the sensor is 3g, and the measuring range is about 0.003kg to 0.05 kg. This indicates that the detection range of the sensor is small, and it is difficult to apply detection in a wide range.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.