CN113267275A - Piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and preparation method thereof - Google Patents
Piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and preparation method thereof Download PDFInfo
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- G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
Abstract
The invention provides a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and a preparation method thereof, wherein the piezoelectric-piezoresistive flexible sensor comprises the following steps: the piezoelectric unit is used for acquiring a multi-point dynamic piezoelectric signal and the piezoresistive unit is used for acquiring a static or low-frequency piezoresistive signal, wherein the piezoelectric unit comprises a first electrode array layer, a piezoelectric sensitive layer and a second common electrode layer; the piezoresistive unit comprises a piezoresistive sensitive layer, an upper packaging layer, a lower packaging layer, a first electrode and a second electrode, wherein the first electrode and the second electrode are symmetrically arranged on two sides of the piezoresistive sensitive layer; the lower surface of the second common electrode layer of the piezoelectric unit is bonded with the upper surface of the upper packaging layer of the piezoresistive unit, so that the piezoelectric unit and the piezoresistive unit are bonded into an integral structure. The invention integrates the piezoelectric effect and the piezoresistive effect in a single device, and can realize the field that the single flexible touch sensor is simultaneously used for dynamic and static cooperative detection by capturing and analyzing signals in real time by utilizing the sensitivity of the piezoelectric unit to high dynamic pressure behaviors and the applicability of the piezoresistive unit to static and low frequency pressure behaviors.
Description
Technical Field
The invention relates to the field of flexible touch sensors, in particular to a piezoelectric-piezoresistive dual-mechanism flexible sensor for dynamic and static cooperative detection.
Background
With the popularization of intelligent terminals, flexible electronic devices are developed vigorously due to the potential of the flexible electronic devices in the fields of human-computer interaction, soft robots and the like, and the flexible touch sensor has wide market prospects due to the wide application of the flexible touch sensor in the fields of electronic skin, medical care and the like. The tactile sensor simulates the tactile sensing function of human skin, and the sensing of the physical property of the measured object or the monitoring of the action of an applicator is completed through the mutual contact between the sensor and the measured object or the specific deformation borne by the sensor.
In terms of mechanism of action, the most widely studied and used flexible tactile sensors are piezoelectric and piezoresistive sensors, respectively. Piezoelectric tactile sensors rely on the piezoelectric effect, in which, when subjected to an external force in a fixed direction, dipoles in the material reorient under the action of an external pressure and form an electric polarization phenomenon inside, resulting in the generation of opposite charges on the upper and lower surfaces of the crystal in proportion to the applied pressure. When the direction of the external force action is changed, the polarity of the charge is changed. Piezoelectric materials commonly used for flexible pressure sensors include polypropylene, PVDF, and P (VDF-TrFE), among others. Similarly, piezoresistive tactile sensors rely on piezoresistive effects, which occur when the resistance response of a material changes regularly with the applied pressure. The active materials commonly used in piezoresistive flexible sensors are mainly based on elastomer 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 create piezoresistive properties.
Due to the combined advantages of simple, scalable, large area, and low cost manufacturing processes, as well as good flexibility, ductility, mechanical stability, and high sensitivity, flexible tactile sensors based on these two mechanisms have been extensively studied by people. In general, much work has been done to improve the performance of individual piezoelectric or piezoresistive sensors due to their respective advantages in dynamic monitoring and static detection. However, limited by a single mechanism, piezoelectric tactile sensors typically do not enable static measurements and have relatively poor sensitivity and reliability at low frequencies. In contrast, flexible piezoresistive tactile sensors typically have poor dynamic response capabilities. Therefore, the two sensors are difficult to meet the requirement that a single flexible pressure sensor realizes high dynamic and static detection capability in the full frequency range, and meanwhile, how to realize multi-point detection of the touch sensor by using the simplest process and improve the preparation efficiency and the detection precision is also an important difficult problem and challenge in the field.
The search of the prior art patent discloses a chinese patent with application number 202011035525.0, which discloses a piezoelectric piezoresistive composite tactile sensor, which also comprises a piezoelectric layer and a piezoresistive layer, but both upper and lower electrodes of the piezoelectric layer are surface electrodes, which cannot realize multi-point array detection, and the other disadvantage is that the electrodes of the piezoresistive layer are designed to be arranged in an upper and lower structure, on one hand, the requirement on the flatness of the surface of the piezoresistive sensitive layer is high, which increases the difficulty of the preparation process, and on the other hand, when the upper and lower electrodes are deposited, the upper and lower electrodes are easily conducted due to the structural defect of the porous piezoresistive sensitive layer, which causes the device to fail.
Based on the above viewpoints, a flexible tactile sensor oriented to multi-point dynamic and static detection, which has a simple process, a high yield and a customizable array structure design, needs to be developed urgently.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection and a preparation method thereof.
The invention provides a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection, which comprises:
the piezoelectric unit is used for collecting multipoint dynamic piezoelectric signals and comprises 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 upper surface of the piezoelectric sensitive layer and consists of a plurality of electrode points which are distributed in an array manner; the second common electrode layer is arranged on the lower surface of the piezoelectric sensitive layer;
the piezoresistive unit is used for acquiring static or low-frequency piezoresistive signals and comprises a piezoresistive sensitive layer, a first electrode, a second electrode, an upper packaging layer and a lower packaging layer, wherein the first electrode and the second electrode are respectively and symmetrically arranged on two sides of the piezoresistive sensitive layer, and the upper packaging layer and the lower packaging layer are respectively arranged on the upper surface and the lower surface of the piezoresistive sensitive layer, the first electrode and the second electrode;
the lower surface of the second common electrode layer of the piezoelectric unit is bonded with the upper surface of the upper packaging layer of the piezoresistive unit in a face-to-face manner, 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 polymers or polymer-based composite materials, so that the flexible tactile sensor can be deformed correspondingly to generate a piezoelectric array signal and a piezoresistive signal respectively when being subjected to an external force.
Preferably, the piezoresistive sensitive layer is made of polyvinylidene fluoride composite materials with porous networking structures modified by graphite nanosheets, and the graphite nanosheets with two-dimensional structures embedded into the porous networking structures are mutually overlapped 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 the single nanofiber of the porous network structure is 50 nanometers to 2 micrometers.
Preferably, the piezoresistive unit has a total thickness of 50-500 microns;
the upper packaging layer and the lower packaging layer are made of Polydimethylsiloxane (PDMS).
Preferably, the piezoelectric sensitive layer is a polyvinylidene fluoride (PVDF) film.
Preferably, the second common electrode layer is a polyethylene terephthalate film plated with indium tin oxide on the surface;
the thickness of the second common electrode layer is 20-100 microns.
Preferably, the material of the first electrode array layer, the first electrode and the second electrode is any one of gold, silver, copper or conductive polymer.
The second aspect of the present invention provides a method for preparing the piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection, including:
patterning and depositing a metal electrode on the upper surface of the piezoelectric sensitive layer to obtain a plurality of electrode points which are distributed on the upper surface of the piezoelectric sensitive layer in an array manner, namely obtaining a first electrode array layer;
bonding the lower surface of the piezoelectric sensitive layer and the upper surface of the second common electrode layer together to obtain a piezoelectric unit;
preparing a piezoresistive sensitive layer;
respectively and symmetrically preparing a first electrode and a second electrode on two sides of the prepared piezoresistive sensitive layer, namely leading out a left electrode and a right electrode on the piezoresistive sensitive layer;
respectively spin-coating an upper packaging layer and a lower packaging layer on the upper surface and the lower surface of the piezoresistive sensitive layer, the first electrode and the second electrode to obtain a piezoresistive unit;
and modifying the piezoelectric unit and the piezoresistive unit into the same size, and bonding the lower surface of the second common electrode layer of the piezoelectric unit and the upper packaging layer of the piezoresistive unit together in a face-to-face mode to obtain the flexible touch sensor.
Preferably, the above-mentioned preparing a piezoresistive sensitive layer comprises:
preparing a polyvinylidene fluoride film with a porous network structure by adopting an electrostatic spinning method;
dispersing graphite nano sheets in a deionized water solution, and carrying out ultrasonic treatment to form a uniformly mixed graphite nano sheet water solution, wherein the graphite nano sheets have a mass fraction of 0.5% -2%;
dipping the prepared polyvinylidene fluoride film into the aqueous solution of the graphite nanosheets, inserting the graphite nanosheet modification skewers into the porous network of the polyvinylidene fluoride film by utilizing ultrasound to construct a conductive network, wherein the ultrasound modification time is 0.5h-2 h.
Compared with the prior art, the invention has at least one of the following beneficial effects:
according to the sensor, the piezoelectric unit and the piezoresistive unit are bonded into a whole in a face-to-face mode, dynamic and static action detection is realized by utilizing a piezoelectric-piezoresistive double mechanism, and multi-point array detection of external dynamic action is realized by patterning the electrode of the piezoelectric unit; meanwhile, the piezoresistance units are arranged on the piezoresistance sensitive layer by the electrodes on the left side and the right side, so that the requirement on the surface flatness of the piezoresistance sensitive layer is lowered, the process is simplified, and the problems of electrode conduction and device failure in the process of sputtering the upper electrode and the lower electrode are solved.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 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 invention;
FIG. 2 is a cross-sectional view of a piezo-piezoresistive flexible sensor for dynamic and static cooperative detection in accordance with a preferred embodiment of the present invention;
the scores in the figure are indicated as: 1 is a first electrode array layer, 2 is a piezoelectric sensitive layer, 3 is a second common electrode layer, 4A is an upper packaging layer, 4B is a lower packaging layer, 5 is a piezoresistive sensitive layer, and 6 is a first electrode.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Referring to fig. 1, 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 is shown, including: a piezoelectric unit and a piezoresistive unit.
The piezoelectric unit is used for collecting multi-point dynamic piezoelectric signals. The piezoelectric unit comprises 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 consists of a plurality of electrode points distributed in an array manner so as to realize multi-channel detection; the first electrode array layer 1 may be prepared by a screen printing technique; the second common electrode layer 3 is arranged on the lower surface of the piezoelectric sensitive layer 2. In one example, the first electrode array layer 1 is prepared on the piezoelectric sensitive layer 2 as N × N independent circular gold electrodes, N being an integer greater than 1; n × N mutually independent electrode arrays can be used for acquiring the distribution condition of the dynamic piezoelectric signals; for example: n equals 3, has realized 3 × 3 array piezoelectricity sensing electrode promptly, when receiving external force to take place deformation, this first electrode array layer 1 can feed back out different array point piezoelectricity signal, and then accurately detect external force dynamic action distribution.
The piezoresistive unit is used for acquiring static or low-frequency piezoresistive signals. The piezoresistive unit comprises 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 disposed on two 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. Because the piezoresistive sensitive layer 5 is of a porous structure, the upper surface and the lower surface of the piezoresistive sensitive layer are inevitably low in flatness; in addition, if metal electrodes are deposited or sputtered on the upper and lower surfaces of the porous structure of the piezoresistive sensitive layer 5 in a face-to-face manner, the electrode conduction condition can occur, and due to the low flatness and the porous structure characteristics of the piezoresistive sensitive layer 5, the upper and lower electrodes prepared on the upper and lower surfaces of the piezoresistive sensitive layer 5 are easy to conduct, namely, the process difficulty is increased from two aspects, and the yield is reduced.
The upper packaging layer 4A and the lower packaging layer 4B are respectively disposed on the upper surface and the lower surface of the piezoresistive sensitive layer 5, the first electrode 6 and the second electrode. The upper and lower encapsulation layers 4A and 4B may be made of a flexible material. The upper packaging layer 4A and the lower packaging layer 4B both play a role in protecting the flexible touch sensor and also achieve a role in avoiding crosstalk with the piezoelectric signal.
The lower surface of the second common electrode layer 3 of the piezoelectric unit and the upper surface of the upper packaging 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 piezoelectric unit and the piezoresistive unit are made of flexible polymers or polymer-based composite materials, so that the flexible tactile sensor can be deformed correspondingly to generate a piezoelectric array signal and a piezoresistive signal respectively when being subjected to an external force.
As a preferable mode, the piezoresistive sensitive layer is an electrostatic spinning polyvinylidene fluoride (PVDF) composite material modified by Graphite Nanosheets (GN) with high conductivity, and the Graphite nanosheets of two-dimensional structures embedded in the electrostatic spinning network are mutually overlapped to form a sensitive three-dimensional conductive network. The porous piezoresistive sensitive film is prepared by adopting an electrostatic spinning method, when the porous piezoresistive sensitive film is acted by the outside, the porous piezoresistive sensitive film can deform, GN (graphite nanosheet) with a two-dimensional structure can approach or depart along with the deformation, the resistance of the piezoresistive sensitive layer is promoted to change, and the detection of the outside acting force is realized by measuring the resistance change. The thickness of the piezoresistive sensitive layer is 10 micrometers-200 micrometers, wherein the diameter of each nanofiber of the porous network structure is 50 nanometers-2 micrometers.
In other preferred embodiments, Polydimethylsiloxane (PDMS) is used as the material of the upper and lower encapsulation layers 4A and 4B. The total thickness of the piezoresistive elements is 50-500 microns.
In other preferred embodiments, the piezoelectric sensitive layer is made of polyvinylidene fluoride (PVDF) film.
In some other preferred embodiments, the second common electrode layer is a polyethylene terephthalate (PET) film coated with Indium Tin Oxide (ITO). The thickness of the second common electrode layer is 20 micrometers to 100 micrometers.
In some other preferred embodiments, the material of the first electrode array layer, the first electrode and the second electrode is any one of gold, silver, copper or conductive polymer. The first electrode array layer, the first electrode and the second electrode can be prepared by any one 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, which comprises the following steps:
s1: and selecting a PVDF film with the thickness of 28 microns as a piezoelectric sensitive layer, and bonding the lower surface of the PVDF film with the ITO-bearing surface of the ITO/PET flexible substrate by using conductive adhesive to finish the preparation of the second common electrode.
S2: preparing a 3 x 3 array circular hard mask by using a laser cutting method, wherein the diameter of each unit is 3 mm, pressing the hard mask and the upper surface of the PVDF film tightly, carrying out magnetron sputtering, and depositing chromium with the thickness of 20 nanometers and a gold array electrode with the thickness of 200 nanometers on the upper surface of the PVDF film in sequence to finish the preparation of a first electrode array to obtain a piezoelectric unit; the piezoelectric unit can meet the multi-point detection of external dynamic action by a method of patterning the upper electrode array, and the accuracy and the recognition degree are improved.
S3: the porous structure in the piezoresistive sensitive layer is prepared by adopting flexible high-molecular PVDF, and specifically, the PVDF porous fiber membrane is prepared by adopting an electrostatic spinning method; firstly, a certain amount of PVDF is dissolved in a mixed solution of N, N-Dimethylformamide (DMF) and acetone (the volume ratio is 2:3), and the proper concentration is adjusted, so that the subsequent spinning work is facilitated.
S4: preparing a PVDF membrane with a porous network structure by adopting an electrostatic spinning method; wherein, in the electrostatic spinning process, the distance between the spinneret and the collecting cylinder is set to be 12 cm, the voltage is 15kV, the extrusion speed is 2mL/h-3mL/h, the rotating speed of the collecting cylinder is 400rpm, the humidity is controlled not to exceed 55% in the electrostatic spinning process, the thickness of the spinning film is in direct proportion to the spinning time, and in general, the spinning time is controlled to be 1-3 hours according to different solution extrusion speeds.
S5: the method is characterized in that an ultrasonic dispersion method is adopted to prepare a conductive GN solution, specifically, a certain amount of GN (graphite nanosheet) is dispersed in a deionized water solution and subjected to ultrasonic treatment for 1h-2h to form a uniformly mixed GN aqueous solution, the GN aqueous solution is used for the next ultrasonic modification treatment, the GN mass fraction is generally between 0.5 wt% and 2 wt%, and the GN mass fraction can be adjusted according to different conditions.
S6: and (2) soaking the PVDF film with the porous networking structure prepared in the step S4 in the GN aqueous solution prepared in the step S5, modifying and cutting two-dimensional GN nanosheets into the porous network of the PVDF film by ultrasonic treatment to construct a sensitive conductive network, wherein the ultrasonic treatment time is related to the ultrasonic power, and in addition, under the condition of the same power, the initial resistance and the sensitivity of the piezoresistive sensitive layer can be controlled and improved by adjusting the ultrasonic treatment time, wherein the ultrasonic modification time is usually 0.5h-2 h.
S7: in order to reduce the requirement of the deposited electrode on the flatness of the film, simplify the process and avoid the problem that the upper and lower electrodes are easy to conduct, a left and right electrode arrangement design is adopted when the piezoresistive layer electrode is prepared, and electrode wires are led out from the left and right ends of the piezoresistive sensitive layer prepared in the step S6.
S8: selecting a PDMS solution as a material of the flexible piezoresistive packaging layer, specifically, mixing a PDMS solution body and a curing agent according to a mass ratio of 10:1, uniformly stirring, pumping out bubbles introduced in the stirring process by using a vacuum oven, then spin-coating on the upper surface and the lower surface of the piezoresistive sensitive layer obtained in S7, wherein the rotating speed is controlled at 500pm-800rpm, the rotating time is 1 minute, then placing the piezoresistive sensitive layer into the vacuum oven, curing for 3 hours at 80 ℃, and performing flexible packaging treatment.
S9: and bonding the piezoelectric unit obtained in the step S2 and the packaged piezoresistive unit obtained in the step S8 in a face-to-face mode by using flexible glue, and finally packaging the whole device by using parylene-C to obtain the piezoelectric-piezoresistive double-mechanism flexible touch sensor.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (10)
1. A piezo-piezoresistive flexible sensor for dynamic and static co-detection, comprising:
the piezoelectric unit is used for collecting multipoint dynamic piezoelectric signals and comprises 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 upper surface of the piezoelectric sensitive layer and consists of a plurality of electrode points which are distributed in an array manner; the second common electrode layer is arranged on the lower surface of the piezoelectric sensitive layer;
the piezoresistive unit is used for acquiring static or low-frequency piezoresistive signals and comprises a piezoresistive sensitive layer, a first electrode, a second electrode, an upper packaging layer and a lower packaging layer, wherein the first electrode and the second electrode are respectively and symmetrically arranged on two sides of the piezoresistive sensitive layer, and the upper packaging layer and the lower packaging layer are respectively arranged on the upper surface and the lower surface of the piezoresistive sensitive layer, the first electrode and the second electrode;
the lower surface of the second common electrode layer of the piezoelectric unit is bonded with the upper surface of the upper packaging layer of the piezoresistive unit in a face-to-face manner, 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 composite materials, so that the flexible tactile sensor can be deformed correspondingly to generate the piezoelectric array signal and the piezoresistive signal respectively when being subjected to an external force.
3. The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 2, wherein the piezoresistive sensitive layer is made of a polyvinylidene fluoride composite material with a porous network structure modified by graphite nanosheets, and the graphite nanosheets with two-dimensional structures embedded in the porous network structure are mutually overlapped to form a sensitive three-dimensional conductive network.
4. The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 3, wherein the thickness of the piezoresistive sensitive layer is 10 microns to 200 microns, and the diameter of the single nanofiber of the porous network structure is 50 nanometers to 2 microns.
5. The piezo-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1, wherein the total thickness of the piezoresistive unit is 50 microns to 500 microns;
the upper packaging layer and the lower packaging layer are made of polydimethylsiloxane.
6. The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1, wherein the piezoelectric sensitive layer is a polyvinylidene fluoride film.
7. The piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 1, wherein the second common electrode layer is a polyethylene terephthalate film coated with indium tin oxide;
the thickness of the second common electrode layer is 20-100 microns.
8. The piezoelectric-piezoresistive flexible sensor for dynamic-static cooperative detection according to any one of claims 1 to 7, wherein the material of the first electrode array layer, the first electrode and the second electrode is any one of gold, silver, copper or conductive polymer.
9. A method for preparing a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to any one of claims 1 to 8, comprising:
patterning and depositing a metal electrode on the upper surface of the piezoelectric sensitive layer to obtain a plurality of electrode points which are distributed on the upper surface of the piezoelectric sensitive layer in an array manner, namely obtaining a first electrode array layer;
bonding the lower surface of the piezoelectric sensitive layer and the upper surface of the second common electrode layer together to obtain a piezoelectric unit;
preparing a piezoresistive sensitive layer;
respectively and symmetrically preparing a first electrode and a second electrode on two sides of the prepared piezoresistive sensitive layer, namely leading out a left electrode and a right electrode on the piezoresistive sensitive layer;
respectively spin-coating an upper packaging layer and a lower packaging layer on the upper surface and the lower surface of the piezoresistive sensitive layer, the first electrode and the second electrode to obtain a piezoresistive unit;
and modifying the piezoelectric unit and the piezoresistive unit into the same size, and bonding the lower surface of the second common electrode layer of the piezoelectric unit and the upper packaging layer of the piezoresistive unit together in a face-to-face mode to obtain the flexible touch sensor.
10. The method for manufacturing a piezoelectric-piezoresistive flexible sensor for dynamic and static cooperative detection according to claim 9,
the preparation of the piezoresistive sensitive layer comprises the following steps:
preparing a polyvinylidene fluoride film with a porous network structure by adopting an electrostatic spinning method;
dispersing graphite nano sheets in a deionized water solution, and carrying out ultrasonic treatment to form a uniformly mixed graphite nano sheet water solution, wherein the graphite nano sheets have a mass fraction of 0.5% -2%;
dipping the prepared polyvinylidene fluoride film into the aqueous solution of graphite nanosheets, inserting the graphite nanosheet modification skewers into the porous network of the polyvinylidene fluoride film by utilizing ultrasound to construct a conductive network, wherein the ultrasound modification time is 0.5h-2 h.
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