CN113267275B - Piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and preparation method thereof - Google Patents

Abstract

The invention provides a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and a preparation method thereof, including: a piezoelectric unit for collecting multi-point dynamic piezoelectric signals and a piezoelectric unit for collecting static or low-frequency piezoresistive signals Piezoresistive unit, wherein the piezoelectric unit includes a first electrode array layer, a piezoelectric sensitive layer and a second common electrode layer; the piezoelectric unit includes a piezoresistive sensitive layer, an upper and lower encapsulation layer, and symmetrically arranged on both sides of the piezoresistive sensitive layer. A first electrode, a second electrode; the lower surface of the second common electrode layer of the piezoelectric unit is bonded with the upper surface of the upper encapsulation layer of the piezoresistive unit, so that the piezoelectric unit and the piezoresistive unit are bonded into an integral structure. The invention unifies the piezoelectric and piezoresistive effects in a single device, utilizes the sensitivity of the piezoelectric unit to high dynamic pressure behavior and the applicability of the piezoresistive unit to static and low-frequency pressure behavior, and can capture and analyze signals in real time. A single flexible tactile sensor can be used in the field of dynamic and static cooperative detection at the same time.

Description

Piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and preparation method

technical field

The invention relates to the field of flexible tactile sensors, in particular to a piezoelectric-piezoresistive dual-mechanism flexible sensor for dynamic and static cooperative detection.

Background technique

With the popularization of smart terminals, flexible electronic devices have flourished due to their potential in human-computer interaction and soft robotics. Among them, flexible tactile sensors have broad applications in electronic skin, medical care and other fields. market prospects. The tactile sensor imitates the tactile perception function of human skin, and completes the perception of the physical properties of the measured object or the monitoring of the action behavior of the applier itself through the mutual contact between the sensor and the measured object, or the specific deformation that the sensor itself undergoes.

In terms of mechanism of action, currently the most studied and applied flexible tactile sensors are piezoelectric and piezoresistive sensors. Piezoelectric tactile sensors rely on the piezoelectric effect. In piezoelectric materials, when subjected to an external force in a certain direction, the dipoles in the material are reoriented and arranged under the action of external pressure and an electric polarization is formed inside, resulting in The upper and lower surfaces of the crystal generate opposite charges proportional to the applied pressure. When the direction of the external force changes, the polarity of the charge also changes. Piezoelectric materials commonly used in flexible pressure sensors include polypropylene, PVDF, and P(VDF-TrFE), among others. Similarly, piezoresistive tactile sensors rely on the piezoresistive effect, which occurs when the resistive response of a material changes regularly with applied pressure. Active materials commonly used in piezoresistive flexible sensors are mainly based on elastomeric composites containing conductive fillers, such as graphene, carbon nanotubes, metal particles, and conductive polymers, which are added to elastomers such as PDMS and polyurethane ) to produce piezoresistive properties.

Due to the simple, scalable, large-area, and low-cost fabrication process and the comprehensive advantages of good flexibility, ductility, mechanical stability, and high sensitivity, flexible tactile sensors based on these two mechanisms have been extensively studied. In general, much work has been done to improve the performance of a single piezoelectric or piezoresistive sensor due to the respective advantages of piezoelectric and piezoresistive sensors in dynamic monitoring and static detection, respectively. However, limited by a single mechanism, piezoelectric tactile sensors generally cannot achieve static measurements and have relatively poor sensitivity and reliability at low frequencies. In contrast, flexible piezoresistive tactile sensors typically have poor dynamic responsiveness. Therefore, it is difficult for these two sensors to meet the requirements of a single flexible pressure sensor to achieve high dynamic and static detection capabilities in the full frequency range. At the same time, how to use the most simplified process to realize multi-point detection of tactile sensors, improve the preparation efficiency and Detection accuracy is also an important problem and challenge in this field.

After searching for prior art documents and patents, it was found that the Chinese patent with the application number of 202011035525.0 discloses a piezo-voltage-resistive composite tactile sensor. The sensor also includes a piezoelectric layer and a piezo-resistive layer. However, the piezoelectric layer The upper and lower electrodes are both surface electrodes, which cannot realize multi-point array detection. Another disadvantage is that the electrodes of the piezoresistive layer are designed to be arranged in an upper and lower structure. On the other hand, when the upper and lower electrodes are deposited, due to the porous structure of the piezoresistive sensitive layer, it is easy to cause the upper and lower electrodes to be turned on, resulting in device failure.

Based on the above viewpoints, a flexible tactile sensor with simple process, high yield, and customizable array structure design for multi-point dynamic and static detection needs to be developed.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and a preparation method thereof.

A first aspect of the present invention provides a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection, comprising:

A piezoelectric unit for collecting multi-point dynamic piezoelectric signals, the piezoelectric unit includes a first electrode array layer, a piezoelectric sensitive layer and a second common electrode layer, wherein the first electrode array layer is arranged on the the upper surface of the piezoelectric sensitive layer, the first electrode array layer is composed of a plurality of electrode points distributed in an array; the second common electrode layer is arranged on the lower surface of the piezoelectric sensitive layer;

A piezoresistive unit for collecting static or low-frequency piezoresistive signals, the piezoresistive unit includes a piezoresistive sensitive layer, a first electrode, a second electrode, an upper encapsulation layer and a lower encapsulation layer, wherein the first electrode, all the The second electrodes are symmetrically arranged on both sides of the piezoresistive sensitive layer, and the upper encapsulation layer and the lower encapsulation layer are respectively arranged on the piezoresistive sensitive layer, the first electrode and the second electrode. upper surface, lower surface;

The lower surface of the second common electrode layer of the piezoelectric unit and the upper surface of the upper encapsulation layer of the piezoresistive unit are bonded face-to-face, so that the piezoelectric unit and the piezoresistive unit are bonded into an integral structure .

Preferably, the piezoelectric unit and the piezoresistive unit are made of flexible polymer or polymer-based composite material, so that the flexible tactile sensor can deform correspondingly as a whole when subjected to external force, and generate piezoelectricity respectively. Array signals and piezoresistive signals.

Preferably, the material of the piezoresistive sensitive layer is a porous networked polyvinylidene fluoride composite material modified by graphite nanosheets, and the two-dimensional graphite nanosheets embedded in the porous networked structure are overlapped with each other to form a sensitive three-dimensional conductive network.

Preferably, the thickness of the piezoresistive sensitive layer is 10 micrometers to 200 micrometers, wherein the diameter of a single nanofiber of the porous network structure is 50 nanometers to 2 micrometers.

Preferably, the total thickness of the piezoresistive unit is 50-500 microns;

The materials of the upper encapsulation layer and the lower encapsulation layer are both polydimethylsiloxane (PDMS).

Preferably, the piezoelectric sensitive layer adopts a polyvinylidene fluoride (PVDF) film.

Preferably, the second common electrode layer is a polyethylene terephthalate film coated with indium tin oxide on the surface;

The thickness of the second common electrode layer is 20 micrometers to 100 micrometers.

Preferably, the materials of the first electrode array layer, the first electrodes and the second electrodes are all selected from any one of gold, silver, copper or conductive polymers.

A second aspect of the present invention provides a method for preparing the piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection, comprising:

A metal electrode is patterned and deposited on the upper surface of the piezoelectric sensitive layer to obtain a plurality of electrode points distributed in an array on the upper surface of the piezoelectric sensitive layer, that is, a first electrode array layer is obtained;

bonding the lower surface of the piezoelectric sensitive layer with the upper surface of the second common electrode layer to obtain a piezoelectric unit;

Preparation of piezoresistive sensitive layer;

A first electrode and a second electrode are respectively prepared symmetrically on both sides of the prepared piezoresistive sensitive layer, that is, the left and right electrodes are drawn from the piezoresistive sensitive layer;

An encapsulation layer and a lower encapsulation layer are spin-coated on the piezoresistive sensitive layer, the upper surface and the lower surface of the first electrode and the second electrode, respectively, to obtain a piezoresistive unit;

The piezoelectric unit and the piezoresistive unit are modified to have the same size, and then the lower surface of the second common electrode layer of the piezoelectric unit and the upper encapsulation layer of the piezoresistive unit are bonded together face-to-face to obtain the flexible tactile sensor.

Preferably, the above-mentioned preparation of the piezoresistive sensitive layer comprises:

Polyvinylidene fluoride film with porous network structure was prepared by electrospinning method;

dispersing the graphite nanosheets in a deionized aqueous solution for ultrasonic treatment to form a uniformly mixed graphite nanosheet aqueous solution, wherein the mass fraction of the graphite nanosheets is 0.5%-2%;

The prepared polyvinylidene fluoride film is immersed in the graphite nanosheet aqueous solution, and the graphite nanosheet is modified and inserted into the porous network of the polyvinylidene fluoride film by ultrasound to construct a conductive network, wherein the ultrasonic modification time 0.5h-2h.

Compared with the prior art, the present invention has at least one of the following beneficial effects:

The above-mentioned sensor of the present invention, by bonding the piezoelectric unit and the piezoresistive element in a face-to-face manner, realizes the dynamic and static action detection by using the piezoelectric-piezoresistive dual mechanism, and realizes the detection of the dynamic and static effects through the electrode pattern design of the piezoelectric unit. Multi-point array detection with external dynamic action; at the same time, the piezoresistive unit is arranged with the left and right electrodes on the piezoresistive sensitive layer design structure, which reduces the requirement for the surface flatness of the piezoresistive sensitive layer, simplifies the process, and avoids sputtering. In the process of upper and lower electrodes, the electrodes are turned on and the device fails.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

1 is a schematic diagram of a three-dimensional overall structure of a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to a preferred embodiment of the present invention;

2 is a cross-sectional view of a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to a preferred embodiment of the present invention;

The marks in the figure are respectively indicated as: 1 is the first electrode array layer, 2 is the piezoelectric sensitive layer, 3 is the second common electrode layer, 4A is the upper encapsulation layer, 4B is the lower encapsulation layer, 5 is the piezoresistive sensitive layer, 6 for the first electrode.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Referring to FIG. 1 , it is a schematic diagram of a three-dimensional overall structure of a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to a preferred embodiment of the present invention, including a piezoelectric unit and a piezoresistive unit.

The piezoelectric unit is used to collect multi-point dynamic piezoelectric signals. The piezoelectric unit includes a first electrode array layer 1, a piezoelectric sensitive layer 2 and a second common electrode layer 3, wherein the first electrode array layer 1 is arranged on the upper surface of the piezoelectric sensitive layer 2, and the first electrode array layer 1 is composed of It is composed of several electrode points distributed in an array to realize multi-channel detection; the first electrode array layer 1 can be prepared by screen printing technology; the second common electrode layer 3 is arranged on the lower surface of the piezoelectric sensitive layer 2 . In an example, the first electrode array layer 1 prepared on the piezoelectric sensitive layer 2 is N*N independent circular gold electrodes, where N is an integer greater than 1; N*N mutually independent electrode arrays can be used for Collect the distribution of dynamic piezoelectric signals; for example, when N is equal to 3, a 3*3 array piezoelectric sensing electrode is realized. When deformed by external force, the first electrode array layer 1 can feedback different array point pressures. The electrical signal is then used to accurately detect the dynamic distribution of the external force.

Piezoresistive units are used to acquire static or low frequency piezoresistive signals. The piezoresistive unit includes a piezoresistive sensitive layer 5 , a first electrode 6 , a second electrode, an upper encapsulation layer 4A and a lower encapsulation layer 4B.

Referring to FIG. 2 , the first electrode 6 and the second electrode are symmetrically arranged on both sides of the piezoresistive sensitive layer 5 , so that the first electrode 6 , the second electrode and the piezoresistive sensitive layer 5 are located on the same layer. Since the piezoresistive sensitive layer 5 has a porous structure, the upper and lower surfaces of the piezoresistive sensitive layer 5 will inevitably have low flatness; , there will be electrode conduction. Due to the low flatness and porous structure of the piezoresistive sensitive layer 5, the preparation of the upper and lower electrodes on and below the piezoresistive sensitive layer 5 is prone to conduction, that is, the increase in the two aspects. The difficulty of the process reduces the yield. Therefore, the above-mentioned piezoresistive unit adopts the strategy of arranging left and right symmetrical electrodes, which effectively avoids these two problems, which not only satisfies the high sensitivity brought by the porous structure of the piezoresistive sensitive layer 5, but also at the same time It also ensures the efficiency and yield in the preparation process, and greatly reduces the difficulty of the process.

The upper encapsulation layer 4A and the lower encapsulation layer 4B are respectively disposed on the upper and lower surfaces of the piezoresistive sensitive layer 5 , the first electrode 6 and the second electrode. The upper encapsulation layer 4A and the lower encapsulation layer 4B may use flexible materials. The upper encapsulation layer 4A and the lower encapsulation layer 4B not only play the role of protecting the flexible tactile sensor, but also realize the role of avoiding crosstalk with piezoelectric signals.

The lower surface of the second common electrode layer 3 of the piezoelectric unit and the upper surface of the upper encapsulation layer 4A of the piezoresistive unit are bonded together in a face-to-face manner, so that the piezoelectric unit and the piezoresistive unit are bonded into an integral structure.

In other preferred embodiments, the materials of the piezoelectric unit and the piezoresistive unit are flexible polymers or polymer-based composite materials, so that when the flexible tactile sensor is subjected to external force, the whole can be deformed correspondingly to generate piezoelectric arrays respectively. signal and piezoresistive signal.

As a preferred method, the piezoresistive sensitive layer is an electrospun polyvinylidene fluoride (PVDF) composite material modified by a highly conductive graphite nanosheet (GN), composed of two-dimensional graphite embedded in an electrospinning network. The nanosheets overlap each other to form a sensitive three-dimensional conductive network. The piezoresistive sensitive layer can be made of a porous piezoresistive sensitive film by an electrospinning method. Since the porous piezoresistive sensitive film is prepared by an electrospinning method, the porous piezoresistive sensitive film will deform when subjected to external action. The GN nanosheets (graphite nanosheets) with two-dimensional structure will approach or move away with the deformation, which will cause the resistance of the piezoresistive sensitive layer to change. The thickness of the piezoresistive sensitive layer is 10 micrometers to 200 micrometers, wherein the diameter of a single nanofiber of the porous network structure is 50 nanometers to 2 micrometers.

In other preferred embodiments, the materials of the upper encapsulation layer 4A and the lower encapsulation layer 4B are both polydimethylsiloxane (PDMS). The total thickness of the piezoresistive elements is 50 microns to 500 microns.

In other preferred embodiments, the piezoelectric sensitive layer adopts polyvinylidene fluoride (PVDF) film.

In other preferred embodiments, the second common electrode layer is a polyethylene terephthalate (PET) film coated with indium tin oxide (ITO) on the surface. The thickness of the second common electrode layer is 20 micrometers to 100 micrometers.

In other preferred embodiments, the materials of the first electrode array layer, the first electrode and the second electrode are all selected from any one of gold, silver, copper or conductive polymers. The first electrode array layer, the first electrode and the second electrode can be prepared by any method of screen printing, magnetron sputtering, electron beam evaporation or brush coating.

In another embodiment, a method for preparing a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection is provided, comprising: performing the following steps:

S1: Select a PVDF film with a thickness of 28 microns as the piezoelectric sensitive layer, and bond the lower surface of the PVDF film with the ITO/PET flexible substrate with conductive glue to complete the preparation of the second common electrode.

S2: Use laser cutting to prepare a 3*3 array of circular hard masks, each with a diameter of 3 mm, press the hard mask and the upper surface of the PVDF film, and perform magnetron sputtering, successively on the upper surface of the PVDF film Depositing 20 nanometers of chromium and 200 nanometers of gold array electrodes to complete the preparation of the first electrode array to obtain a piezoelectric unit; the method of patterning the upper electrode array enables the piezoelectric unit to satisfy multiple points of external dynamic action detection to improve accuracy and recognition.

S3: The porous structure in the piezoresistive sensitive layer is prepared by flexible polymer PVDF. Specifically, the PVDF hollow fiber membrane is prepared by electrospinning method; a certain amount of PVDF is first dissolved in N,N-dimethylformamide (DMF) and acetone in the mixed solution (volume ratio of 2:3), adjusting the appropriate concentration is conducive to the next spinning work.

S4: PVDF membrane with porous network structure is prepared by electrospinning method; wherein, during the electrospinning process, the distance between the spinneret and the collecting cylinder is set to 12 cm, the voltage is 15 kV, and the extrusion speed is 2 mL /h-3mL/h, the speed of the collecting cylinder is 400rpm, the humidity during the electrospinning process is controlled not to exceed 55%, the thickness of the spinning film is proportional to the spinning time, in general, according to different solution extrusion speeds, spinning Silk time is controlled between 1-3 hours.

S5: The conductive GN solution is prepared by ultrasonic dispersion method. Specifically, a certain amount of GN (graphite nanosheets) is dispersed in a deionized aqueous solution for 1h-2h ultrasonic treatment to form a uniformly mixed GN aqueous solution, and the GN aqueous solution is used for the next ultrasonic modification Treatment, the mass fraction of GN is generally between 0.5wt% and 2wt%, which can be adjusted according to different situations.

S6: Immerse the PVDF membrane with porous network structure prepared in step S4 in the GN aqueous solution prepared in step S5, and use ultrasonic treatment to modify the two-dimensional GN nanosheets into the porous network of the PVDF membrane to construct a sensitive conductive network. , among which, the ultrasonic treatment time is related to the ultrasonic power. In addition, under the same power, the initial resistance of the piezoresistive sensitive layer can be controlled and the sensitivity can be improved by adjusting the ultrasonic treatment time. Generally speaking, the ultrasonic modification time is 0.5h -2h.

S7: In order to reduce the requirements for the film flatness of the deposition electrodes, simplify the process, and avoid the problem that the upper and lower electrodes are easily turned on, the left and right electrode layout design is adopted when preparing the piezoresistive layer electrodes, and the piezoresistive sensitive electrodes prepared in step S6 Electrode lines are drawn from the left and right ends of the layer.

S8: Select the PDMS solution as the material of the flexible piezoresistive encapsulation layer. Specifically, the PDMS solution body and the curing agent are mixed in a mass ratio of 10:1, and after stirring evenly, the bubbles introduced during the stirring process are extracted by a vacuum oven, and then spin-coated The upper and lower surfaces of the piezoresistive sensitive layer obtained in S7, wherein the rotation speed is controlled at 500pm-800rpm, the rotation time is 1 minute, and then placed in a vacuum oven, cured at 80°C for 3h, and flexible packaging is performed.

S9: The piezoelectric unit obtained in S2 and the packaged piezoresistive unit obtained in S8 are bonded face-to-face with flexible glue, and finally the whole device is packaged with parylene-C to obtain a piezoelectric-piezoresistive dual-mechanism flexible tactile sensor.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (7)

1. A piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection, characterized in that, comprising: A piezoelectric unit for collecting multi-point dynamic piezoelectric signals, the piezoelectric unit includes a first electrode array layer, a piezoelectric sensitive layer and a second common electrode layer, wherein the first electrode array layer is arranged on the the upper surface of the piezoelectric sensitive layer, the first electrode array layer is composed of a plurality of electrode points distributed in an array; the second common electrode layer is arranged on the lower surface of the piezoelectric sensitive layer; A piezoresistive unit for collecting static or low-frequency piezoresistive signals, the piezoresistive unit includes a piezoresistive sensitive layer, a first electrode, a second electrode, an upper encapsulation layer and a lower encapsulation layer, wherein the first electrode, all the The second electrodes are symmetrically arranged on both sides of the piezoresistive sensitive layer, and the upper encapsulation layer and the lower encapsulation layer are respectively arranged on the piezoresistive sensitive layer, the first electrode and the second electrode. The upper surface and the lower surface; the material of the piezoresistive sensitive layer is a porous networked polyvinylidene fluoride composite material modified by graphite nanosheets, and the graphite nanosheets are fixed on the porous networked structure polyvinylidene by ultrasonic cutting. In the vinylidene fluoride composite material, the two-dimensional graphite nanosheets embedded in the porous network structure overlap each other to form a sensitive three-dimensional conductive network; the thickness of the piezoresistive sensitive layer is 10 μm-200 μm, wherein, the The diameter of a single nanofiber of the porous networked structure is 50 nanometers to 2 micrometers; The lower surface of the second common electrode layer of the piezoelectric unit and the upper surface of the upper encapsulation layer of the piezoresistive unit are bonded face-to-face, so that the piezoelectric unit and the piezoresistive unit are bonded into an integral structure . 2 . The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1 , wherein the piezoelectric unit and the piezoresistive unit are made of flexible polymer or polymer-based materials. 3 . The composite material enables the flexible sensor to undergo corresponding deformation as a whole when it is subjected to external force, generating piezoelectric array signals and piezoresistive signals respectively. 3. The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1, wherein the total thickness of the piezoresistive unit is 50-500 microns; Both the upper encapsulation layer and the lower encapsulation layer are made of polydimethylsiloxane. 4 . The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1 , wherein the piezoelectric sensitive layer adopts a polyvinylidene fluoride film. 5 . 5 . The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1 , wherein the second common electrode layer is polyethylene terephthalate whose surface is plated with indium tin oxide. 6 . Alcohol ester film; The thickness of the second common electrode layer is 20 micrometers to 100 micrometers. 6. The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to any one of claims 1-5, wherein the first electrode array layer, the first electrode and the first electrode The material of the two electrodes is any one of gold, silver, copper or conductive polymer. 7. A method for preparing a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to any one of claims 1-6, characterized in that, comprising: A metal electrode is patterned and deposited on the upper surface of the piezoelectric sensitive layer to obtain a plurality of electrode points distributed in an array on the upper surface of the piezoelectric sensitive layer, that is, a first electrode array layer is obtained; bonding the lower surface of the piezoelectric sensitive layer with the upper surface of the second common electrode layer to obtain a piezoelectric unit; The preparation of the piezoresistive sensitive layer includes: preparing a polyvinylidene fluoride film with a porous network structure by an electrospinning method; dispersing the graphite nanosheets in a deionized aqueous solution for ultrasonic treatment to form a uniformly mixed graphite nanosheet aqueous solution, wherein, The mass fraction of the graphite nanosheet is 0.5%-2%; the prepared polyvinylidene fluoride film is immersed in the graphite nanosheet aqueous solution, and the graphite nanosheet is modified and inserted into the polyvinylidene by ultrasonic In the porous network of the vinyl fluoride film, a conductive network is constructed, wherein the ultrasonic modification time is 0.5h-2h; the thickness of the piezoresistive sensitive layer is 10 μm-200 μm, wherein the single nanometer of the porous network structure is The fiber diameter is 50 nanometers to 2 micrometers; A first electrode and a second electrode are respectively prepared symmetrically on both sides of the prepared piezoresistive sensitive layer, that is, the left and right electrodes are drawn from the piezoresistive sensitive layer; An encapsulation layer and a lower encapsulation layer are spin-coated on the piezoresistive sensitive layer, the upper surface and the lower surface of the first electrode and the second electrode, respectively, to obtain a piezoresistive unit; The piezoelectric unit and the piezoresistive unit are modified to have the same size, and then the lower surface of the second common electrode layer of the piezoelectric unit and the upper encapsulation layer of the piezoresistive unit are bonded together face-to-face to obtain Flexible sensor.

Images