CN110987248B - Flexible touch sensor and preparation method thereof - Google Patents

Abstract

Translated fromChinese

本发明涉及一种柔性触觉传感器，包括相互导电连接的压电驻极体电缆传感单元和压电薄膜传感单元，所述的压电驻极体电缆传感单元包括从内到外依次同轴连接的芯电极、压电驻极体层和屏蔽层以及护套保护层，所述的压电薄膜传感单元包括纵向分布并依次连接的第一电极层、压电材料层和第二电极层，所述屏蔽层连接压电电缆接地引线，所述第一电极层连接压电薄膜第一电极引线，所述第二电极层连接压电薄膜第二电极引线。与现有技术相比，可同时测量正应力和切应力。

The invention relates to a flexible tactile sensor, comprising a piezoelectric electret cable sensing unit and a piezoelectric thin film sensing unit which are electrically connected to each other. A shaft-connected core electrode, a piezoelectric electret layer, a shielding layer, and a sheath protective layer, the piezoelectric thin-film sensing unit includes a first electrode layer, a piezoelectric material layer, and a second electrode that are longitudinally distributed and connected in sequence The shielding layer is connected to the ground lead of the piezoelectric cable, the first electrode layer is connected to the first electrode lead of the piezoelectric film, and the second electrode layer is connected to the second electrode lead of the piezoelectric film. In contrast to the prior art, both normal stress and shear stress can be measured simultaneously.

Description

Flexible touch sensor and preparation method thereof

Technical Field

The invention relates to the technical field of sensing, in particular to a flexible touch sensor and a preparation method thereof.

Background

With the rapid development of the flexible sensor technology and the wireless communication technology, the development of intelligentization, good flexibility and ductility, wearable sensors and sensing systems is promoted, and particularly in the fields of artificial intelligent robots, industrial equipment, medical instruments, remote medical treatment, health monitoring and the like, the application prospect of the flexible touch sensor is very wide. Therefore, the performance requirements for flexible sensors are increasing. At present, most of the existing piezoelectric sensors only use rigid sensing materials as transduction materials, and the relative rigidity of the sensors is large, so that the overall flexibility of the sensors is restricted. On the other hand, although most of flexible sensors using flexible piezoelectric materials as transduction materials can measure normal stress and shear stress, the separation of the normal stress and the shear stress has certain difficulty, and the three-dimensional stress of a contact interface cannot be accurately measured and analyzed, so that the further application field of the sensors is limited.

Disclosure of Invention

The present invention is directed to overcome the above-mentioned drawbacks of the prior art and to provide a flexible tactile sensor capable of measuring normal stress and shear stress simultaneously and a method for manufacturing the same.

The purpose of the invention can be realized by the following technical scheme:

the utility model provides a flexible touch sensor, includes piezoelectric electret cable sensing unit and piezoelectric film sensing unit of mutual conductive connection, piezoelectric electret cable sensing unit include core electrode, piezoelectric electret layer, the shielding layer of coaxial coupling in proper order from inside to outside to and the sheath protective layer, piezoelectric film sensing unit including longitudinal distribution and the first electrode layer, piezoelectric material layer and the second electrode layer that connect gradually, piezoelectric cable ground lead is connected to the shielding layer, the first electrode layer is connected the first electrode lead of piezoelectric film, the second electrode layer is connected piezoelectric film second electrode lead.

The polarization direction of the piezoelectric electret layer takes the core electrode as the center and is distributed in the radial direction.

The piezoelectric electret cable sensing unit and the electrode lead of the piezoelectric film sensing unit are bonded through a conductive material.

The piezoelectric electret cable sensing units are arranged on the piezoelectric film sensing units in a V-shaped, U-shaped, S-shaped, spiral-shaped and other wiring modes.

The piezoelectric electret cable sensing unit and the piezoelectric film sensing unit are packaged by polymers.

The piezoelectric electret of the piezoelectric electret layer is a unipolar or bipolar piezoelectric electret.

A preparation method of the flexible touch sensor comprises the following steps:

step S1: making a microporous structure film by using a polymer;

step S2: charging the film to obtain a piezoelectric electret layer;

step S3: the piezoelectric electret layer is coaxially connected to the outer side of the core electrode, and the shielding layer is coaxially connected to the outer side of the piezoelectric electret layer;

step S4: leading out a piezoelectric cable grounding lead from the shielding layer to obtain a piezoelectric electret cable sensing unit;

step S5: covering a layer of thin film electrode on each of the upper surface and the lower surface of the piezoelectric material layer to obtain a first electrode layer and a second electrode layer;

step S6: leading out a first electrode lead from the first electrode layer, and leading out a second electrode lead from the second electrode layer to obtain a piezoelectric film sensing unit;

step S7: the piezoelectric film sensing unit is in conductive connection with the piezoelectric electret cable sensing unit.

Compared with the prior art, the invention has the following advantages:

(1) the piezoelectric electret cable sensing unit and the piezoelectric film sensing unit are in conductive connection, when the sensor is pressed, the piezoelectric electret cable sensing unit on the upper portion and the piezoelectric film sensing unit on the lower portion can simultaneously generate electric signals, when the sensor is subjected to shearing force, only the piezoelectric electret cable sensing unit on the upper portion can generate the electric signals, and therefore positive stress and shearing stress of an interface can be separated.

(2) The piezoelectric material of the piezoelectric sensing unit is a porous piezoelectric electret, and has better piezoelectric performance.

(3) The device has the remarkable advantages of wide measurement range, high sensitivity, simple structure, high flexibility, low cost, long service life and the like, and can be applied to the emerging fields of embedded and implantable biosensors, medical health detection equipment, robot sliding sensors, robot electronic skins and the like.

(4) The sheath layer can strengthen the intensity of the piezoelectric electret cable sensing unit and prevent the piezoelectric electret cable sensing unit from being damaged.

(5) The piezoelectric electret can be wound on the core electrode in a spiral mode, the bending performance can be improved, the tensile strength is improved, the piezoelectric electret cable sensing unit is more round, and the appearance is more attractive.

(6) The piezoelectric electret cable sensing unit and the electrode lead of the piezoelectric film sensing unit are bonded through the conductive material, so that the implementation is convenient, and good conductive performance can be provided.

(7) The piezoelectric electret cable sensing units are arranged in the piezoelectric film sensing units in a V-shaped, U-shaped, S-shaped, spiral and other wiring modes, and compared with linear arrangement, the piezoelectric electret cable sensing units have the advantages that the area capable of measuring pressure is larger, and flexibility is better.

(8) By adopting the polymer encapsulation, the touch sensor can keep good flexibility, is acid-resistant, corrosion-resistant and aging-resistant, and can well protect devices.

Drawings

FIG. 1 is a schematic diagram of a flexible tactile sensor according to the present invention;

FIG. 2 is a schematic diagram of a U-shaped wiring scheme according to the present invention;

FIG. 3 is a schematic view of a V-shaped wiring scheme according to the present invention;

reference numerals:

1 is a sheath layer; 2 is a shielding layer; 3 is a piezoelectric electret layer; 4 is a core electrode; 5 is a first electrode layer; 6 is a piezoelectric material layer; 7 is a second electrode layer; 8 is a piezoelectric cable grounding lead; 9 is a first electrode lead; and 10, a second electrode lead.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Examples

The embodiment provides a flexible touch sensor, which is composed of two parts connected by conductive adhesive, and has an upper structure and a lower structure, wherein the upper part is a piezoelectric electret cable sensing unit, and the lower part is a piezoelectric film sensing unit. The piezoelectric electret cable sensing unit consists of four parts, is coaxially connected with a structure and sequentially comprises acore electrode 4, apiezoelectric electret layer 3, a shielding layer 2 and a sheath layer 1 from inside to outside. The innermost layer is acore electrode 4, thepiezoelectric electret layer 3 is a porous piezoelectric electret film, the porous piezoelectric electret film is spirally wound and wraps thecore electrode 4, the porous piezoelectric electret film is woven and wrapped by a shielding layer 2 made of conductive materials (such as copper or aluminum), the outermost layer is a high-density polyethylene protective sleeve and is used for protecting the whole cable, and the polarization direction of thepiezoelectric electret layer 3 takes thecore electrode 4 as the center and is radially and symmetrically distributed. The piezoelectric film sensing unit is composed of three parts, wherein the piezoelectric film sensing unit is of a vertically symmetrical structure, the upper surface and the lower surface are respectively afirst electrode layer 5 and asecond electrode layer 7, the middle part is apiezoelectric material layer 6, the piezoelectric material can be PVDF polymer, piezoelectric electret and the like, a shielding layer 2 is connected with a piezoelectriccable grounding lead 8, thefirst electrode layer 5 is connected with a piezoelectric filmfirst electrode lead 9, and thesecond electrode layer 7 is connected with a piezoelectric filmsecond electrode lead 10. When the flexible touch sensor is pressed (normal stress), the piezoelectric electret cable sensing unit on the upper part and the piezoelectric film sensing unit on the lower part can simultaneously generate electric signals, and when the flexible touch sensor is subjected to shearing force (shearing stress), only the piezoelectric electret cable sensing unit on the upper part can generate the electric signals, so that the normal stress and the shearing stress of an interface can be separated. The flexible touch sensor has the remarkable advantages of wide measurement range, high sensitivity, simple structure, high flexibility, low cost, long service life and the like, and can be applied to the emerging fields of embedded and implantable biosensors, medical health detection equipment, robot sliding sensors, robot electronic skins and the like.

The preparation method of the flexible touch sensor comprises the following steps: (1) a polymer (such as PTFE, FEP, COC, PET, PI, PE, PEN, PP, PLA, PBAT, CYTOP and the like) is selected to be made into an internal porous structure film (namely, the microporous structure film has different sizes of holes made of different materials, for the PP film, the transverse size of the unexpanded holes is about 100um, the longitudinal size of the unexpanded holes is 5um, and after expansion, the longitudinal size of the expanded holes is about twice of the initial value), and a micro-nano pore structure is contained in the porous structure film. (2) Charging the porous structure film by using corona polarization, contact method charging, ion implantation, electron beam implantation and other modes to form a piezoelectric electret film, so as to obtain apiezoelectric electret layer 3; (3) selecting a conductive material as a core electrode 4 (such as aluminum alloy, copper and silver), and cutting the piezoelectric electret film and then spirally winding the cut piezoelectric electret film on thecore electrode 4 in a bidirectional manner; (4) selecting a conductive material (copper or aluminum) to prepare a shielding layer 2, and weaving and wrapping the spirally wound porous piezoelectric electret; (5) protecting the whole cable by using a high-density polyethylene sheath, and leading out a piezoelectriccable grounding lead 8 from the shielding layer 2, so that the piezoelectric electret cable sensing unit is prepared; (6) selecting a piezoelectric material (PVDF polymer, piezoelectric electret) as apiezoelectric material layer 6 of a piezoelectric film sensing unit, and covering a layer of film electrode made of aluminum on each of the upper surface and the lower surface of the piezoelectric material layer to obtain afirst electrode layer 5 and asecond electrode layer 7; (7) respectively sticking an electrode lead to thefirst electrode layer 5 and thesecond electrode layer 7 to obtain afirst electrode lead 9 and asecond electrode lead 10, and finally manufacturing a piezoelectric thin film sensing unit; (8) the piezoelectric cable sensing unit and the piezoelectric film sensing unit are arranged up and down and can be fixed together through glue and the like, and the electrode leads are bonded by conductive adhesive tapes or conductive adhesives; (9) the piezoelectric cable sensing unit is wired on the piezoelectric film sensing unit in various ways, such as a U-shaped wiring way, a V-shaped wiring way, an S-shaped wiring way, a spiral wiring way and the like; (10) the whole flexible touch sensor is packaged and cured by PDMS, and the PDMS material has the advantages of acid resistance, corrosion resistance, aging resistance and the like, so that the device can be well protected.

The following is a specific example:

(1) selecting a commercial PQ50 porous membrane with the thickness of 50 mu m as a raw material, and cutting a sample membrane into a square with the thickness of 10cm multiplied by 10 cm; (2) performing pressure puffing treatment, placing the sample in an autoclave with the pressure of 1.9MPa and the temperature of 110 ℃, preserving the heat for 3.5 hours, immediately quickly reducing the pressure in the autoclave to the ambient air pressure, taking out the sample, and cooling to the room temperature; (3) performing corona polarization treatment on the bulked PQ50 porous membrane, wherein the corona voltage is-25 kV and the time is 60s during polarization, and the porous piezoelectric electret is prepared; (4) selecting an inner conductor made of an aluminum alloy material as a core electrode, wherein the section of the inner conductor is a right circle, slitting the porous piezoelectric electret, and spirally winding a strip-shaped porous piezoelectric electret on the core electrode by a wrapping method; (5) the shielding layer is a copper mesh formed by weaving copper wires and wraps the spirally wound porous piezoelectric electret; (6) protecting the whole cable by using a high-density polyethylene sheath, and leading out an electrode lead at the position of the shielding layer 2, so that the piezoelectric electret cable sensing unit is prepared; (7) coating 100nm thick aluminum electrodes on the upper and lower surfaces of the porous piezoelectric electret as a piezoelectric material layer by a vacuum evaporation method; (8) respectively sticking an electrode lead at the end parts of the two electrodes to finally manufacture a piezoelectric film sensing unit; (9) the piezoelectric electret cable sensing unit and the piezoelectric film sensing unit are arranged up and down, and the contact part of the electrodes is bonded by a conductive adhesive tape; (10) arranging piezoelectric electret cable sensing units on the surface of a piezoelectric film sensing unit in a U shape, wherein the distance is 2 mm; (11) finally, the whole device is packaged and cured by PDMS.

The flexible touch sensor can be used for detecting positive pressure and frictional force of a sole, a force measuring insole model is drawn by utilizing three-dimensional modeling software such as Solidworks and the like, a force measuring insole is quickly and accurately manufactured by utilizing a 3D printing technology and adopting Polyamide (PA) as a 3D printing material through 3D printing equipment, and the whole flexible touch sensor is embedded into the force measuring insole, so that the force measuring insole capable of simultaneously detecting the positive pressure and the frictional force of the sole is prepared.

Claims (7)

1. A flexible touch sensor is characterized in that the flexible touch sensor is composed of two parts connected by conductive adhesive, and the flexible touch sensor is of an upper structure and a lower structure, wherein the upper part is a piezoelectric electret cable sensing unit, and the lower part is a piezoelectric film sensing unit; the piezoelectric electret cable sensing unit comprises a core electrode (4), a piezoelectric electret layer (3) and a shielding layer (2) which are sequentially and coaxially connected from inside to outside, the piezoelectric electret cable sensing unit comprises a first electrode layer (5), a piezoelectric material layer (6) and a second electrode layer (7) which are longitudinally distributed and sequentially connected, the shielding layer (2) is connected with a piezoelectric cable grounding lead (8), the first electrode layer (5) is connected with a piezoelectric film first electrode lead (9), and the second electrode layer (7) is connected with a piezoelectric film second electrode lead (10); the piezoelectric electret cable sensing units are arranged on the piezoelectric film sensing units in a V-shaped, U-shaped, S-shaped or spiral wiring mode.

2. A flexible tactile sensor according to claim 1, wherein said shield layer (2) is coaxially and externally connected to said sheath layer (1).

3. A flexible tactile sensor according to claim 1, wherein the piezoelectric electret of the piezoelectric electret layer (3) has a polarization direction which is radially symmetrical about the core electrode (4).

4. A flexible tactile sensor according to claim 1, wherein the piezoelectric electret cable sensing element and the electrode leads of the piezoelectric thin film sensing element are bonded by a conductive material.

5. A flexible touch sensor according to claim 1, wherein the piezoelectric electret cable sensing element and the piezoelectric thin film sensing element are polymer encapsulated.

6. A flexible tactile sensor according to claim 1, characterized in that the piezoelectrets of the piezoelectrets layer (3) are unipolar piezoelectrets or bipolar piezoelectrets.

7. A method of making a flexible touch sensor according to any of claims 1-6, comprising the steps of:

step S1: making a microporous structure film by using a polymer;

step S2: charging the film to obtain a piezoelectric electret layer (3);

step S3: the piezoelectric electret layer (3) is coaxially connected to the outer side of the core electrode (4), and the shielding layer (2) is coaxially connected to the outer side of the piezoelectric electret layer (3);

step S4: a piezoelectric cable grounding lead (8) is led out of the shielding layer (2) to obtain a piezoelectric electret cable sensing unit;

step S5: respectively covering a layer of thin film electrode on the upper surface and the lower surface of the piezoelectric material layer (6) to obtain a first electrode layer (5) and a second electrode layer (7);

step S6: a first electrode lead (9) is led out from the first electrode layer (5), and a second electrode lead (10) is led out from the second electrode layer (7), so that the piezoelectric thin film sensing unit is obtained;

step S7: the piezoelectric film sensing unit is in conductive connection with the piezoelectric electret cable sensing unit.

Images