CN112338948B - Piezoelectric piezoresistive composite humanoid tactile finger and preparation method thereof - Google Patents

Piezoelectric piezoresistive composite humanoid tactile finger and preparation method thereof Download PDF

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CN112338948B
CN112338948B CN202011462012.8A CN202011462012A CN112338948B CN 112338948 B CN112338948 B CN 112338948B CN 202011462012 A CN202011462012 A CN 202011462012A CN 112338948 B CN112338948 B CN 112338948B
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layer
piezoelectric
wire
piezoresistive
flexible
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CN112338948A (en
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俞平
周平
张慧霞
陈凤楠
龙江启
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Wenzhou University
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Wenzhou University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J15/00—Gripping heads and other end effectors
    • B25J15/0009—Gripping heads and other end effectors comprising multi-articulated fingers, e.g. resembling a human hand
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J13/00—Controls for manipulators
    • B25J13/08—Controls for manipulators by means of sensing devices, e.g. viewing or touching devices
    • B25J13/081—Touching devices, e.g. pressure-sensitive
    • B25J13/084—Tactile sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C69/00—Combinations of shaping techniques not provided for in a single one of main groups B29C39/00 - B29C67/00, e.g. associations of moulding and joining techniques; Apparatus therefore
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges

Abstract

The invention discloses a piezoelectric piezoresistive composite humanoid tactile finger and a preparation method thereof.A humanoid tactile finger body consists of a finger-shaped substrate, a piezoelectric piezoresistive sensitive array and a bionic fingerprint, wherein the piezoelectric piezoresistive sensitive array is embedded on the surface layer of the finger-shaped substrate, and the bionic fingerprint covers the surface layer; the piezoelectric piezoresistive sensitive array consists of a plurality of sensitive units; the sensitive unit consists of a flexible packaging layer, a silicone oil liquid layer, a piezoelectric wire, a piezoresistive wire, a flexible cavity layer and a flexible substrate layer; the piezoelectric wire is composed of a first tungsten wire, a PVDF piezoelectric layer and a first copper-plated conductive layer from inside to outside in sequence, and the piezoelectric wire is composed of a second tungsten wire, a conductive rubber layer and a second copper-plated conductive layer from inside to outside in sequence. The piezoelectric wire and the piezoresistive wire respectively bear the measurement of dynamic force and static force, can improve the composite measurement function of the human-simulated tactile finger on the distributed dynamic and static force of the high-density curved surface, and provide rich contact force feedback information for the stable operation and accurate identification of the bionic artificial hand on an object.

Description

Piezoelectric piezoresistive composite humanoid tactile finger and preparation method thereof
Technical Field
The invention relates to a composite humanoid tactile finger, in particular to a piezoelectric piezoresistive composite humanoid tactile finger and a preparation method thereof.
Background
The human hand can sense the external environment and can reliably complete the operation of various objects (such as grabbing objects), which is easy to sense the small body by distributing abundant mechanical stimulation in the skin of the human hand. These bodies can be divided into four classes according to their structure: the zona pellucida (FAII), the merlinosomes (FAII), the lafenill corpuscles (SAII), and the merkel palpate (SAI). The first two bodies are fast reaction bodies, sensitive to dynamic force and mainly used for sensing high-frequency vibration signals; the latter two bodies are slow reaction bodies, sensitive to static force and capable of sensing tangential force, contact force and distribution thereof.
The intelligent artificial limb is required to complete dexterous operation and environment perception like a human hand, and has multiple touch functions, such as normal force and tangential force detection, slippage detection, object surface feature recognition and the like. The touch function is realized by installing a touch sensor on the surface or in the artificial hand, and the artificial hand and the touch sensor have certain flexibility in order to adapt to the surface shape of an object in the contact process. Most current tactile sensor arrays are mounted on the surface of a prosthetic hand to provide tactile feedback, but such direct contact is prone to damage to the tactile sensors. Therefore, it is necessary to design a human-like tactile finger with an embedded tactile array, which has the characteristics of good flexibility, fast response, and distributed measurement, and can provide feedback information in time so as to stably grasp an object.
Disclosure of Invention
The invention aims to provide a piezoelectric piezoresistive composite humanoid tactile finger and a preparation method thereof, and aims to solve the problems in the background technology.
In order to achieve the purpose, the invention provides a piezoelectric piezoresistive composite humanoid tactile finger, which comprises a humanoid tactile finger body, wherein the humanoid tactile finger body consists of a bionic fingerprint, a piezoelectric piezoresistive sensitive array and a finger-shaped substrate in sequence from top to bottom;
the piezoelectric piezoresistive sensitive array is composed of a plurality of sensitive units, each sensitive unit comprises a flexible packaging layer and a flexible substrate layer, a sealing cavity is formed between the flexible packaging layer and the flexible substrate layer, and a silicon oil liquid layer is filled in the sealing cavity to serve as a hydraulic pressure conducting medium; the silicon oil liquid layer is internally provided with piezoelectric wires and piezoresistive wires, and the piezoelectric wires and the piezoresistive wires penetrate through the flexible substrate layer and extend to the outside of the finger-shaped substrate so as to be connected with external electrode leads; a flexible cavity layer is arranged between the piezoelectric wires and the flexible substrate layer and between the piezoresistive wires and the flexible substrate layer;
the piezoelectric wire is composed of a first tungsten wire, a PVDF piezoelectric layer and a first copper-plated conducting layer from inside to outside in sequence; the piezoresistive thread is composed of a second tungsten wire, a conductive rubber layer and a second copper-plated conductive layer from inside to outside in sequence.
The further setting is that: the number of the sensitive units on the piezoelectric piezoresistive sensitive array is 531.
The further setting is that: the piezoelectric piezoresistive sensitive array is positioned under the humanoid fingerprint, the spatial resolution is 1mm, and the integral distribution area is 426mm2。
The further setting is that: the flexible substrate layer is provided with through holes for the piezoelectric threads and the piezoresistive threads to pass through respectively, and the center distance between the two through holes is 324 microns.
The further setting is that: the piezoelectric wire is of a Z-shaped structure, and the piezoresistive wire is of a C-shaped structure.
The further setting is that: the flexible packaging layer, the flexible cavity layer and the flexible substrate layer are all molded by PDMS materials through casting, the overall size of the flexible cavity layer is 100 micrometers multiplied by 50 micrometers, and a cuboid cavity with the size of 80 micrometers multiplied by 40 micrometers is arranged in the flexible cavity layer.
The invention also provides a preparation method of the piezoelectric piezoresistive composite humanoid tactile finger, which comprises the following steps:
step S1, putting PVDF particles into a constant-temperature stainless steel container at 80 ℃ for 1 hour, stirring once every 5 minutes, and then melting in a constant-temperature furnace at 180 ℃; putting the molten PVDF into a hopper of an extruder, enabling a tungsten wire with the length of 30m and the diameter of 0.03mm to pass through a metal pipe, enabling the temperature of the hopper and a neck mold to be constant at 180 ℃, enabling the rotation speed of a screw to be 10r/min, extruding the tungsten wire through a circular neck mold with the radius of 22 mu m, shaping the tungsten wire through a double-roller open mill, cooling the tungsten wire to obtain the tungsten wire with the PVDF coated on the surface, and cutting the tungsten wire into small sections with the length of 50 mm;
step S2, cutting the blank in the step S1The good small sections are tiled on a clamp and are arranged on a rotary drum of a multi-target magnetron sputtering coating machine, and copper with the purity of 99.99 percent is arranged on a cathode target; pumping the air pressure in the vacuum chamber to 5 × 10-3Pa, introducing argon gas which is a sputtering gas with the purity of 99.99 percent, and electrifying 50mA direct current between the cathode and the anode to obtain the piezoelectric wire with the surface covered with the copper metal coating, wherein the thickness of the piezoelectric wire is 10 mu m;
step S3, immersing the piezoelectric wire prepared in the step S2 in a DMF solution for 2mm to dissolve the PVDF piezoelectric layer, exposing a conductive core with the length of 2mm, and then polarizing the piezoelectric wire by utilizing piezoelectric fiber polarizing equipment; immersing a piezoelectric wire into methyl silicone oil, wherein a tungsten wire is used as an anode, and a copper-plated conductive layer is used as a cathode; polarizing at 70 ℃ by applying 1000V voltage for 60min, and taking out after methyl silicone oil is cooled to room temperature;
step S4, preparing conductive rubber, wherein the raw materials are carbon black, silicon rubber, petroleum ether and nano SiO2The silane coupling agent, dibutyltin dilaurate and vulcanizing agent ethyl orthosilicate in a ratio of 2.5: 10: 6: 2: 0.3: 0.3: 0.7; diluting silicon rubber and petroleum ether in proportion, and then sequentially adding carbon black and SiO2Stirring the silane coupling agent and the dibutyltin dilaurate for 5min to uniformly mix the components, adding ethyl orthosilicate, continuously stirring the mixture for 5min, and vacuumizing the mixed solution to prepare a conductive rubber mixed solution; pouring the mixed solution into a hopper of an extruder, enabling a tungsten wire with the length of 30m and the diameter of 0.03mm to pass through a metal tube, keeping the temperature of the hopper and an opening die at 50 ℃, enabling the rotation speed of a screw to be 60r/min, extruding through a circular opening die with the radius of 22 mu m, and collecting the prepared conductive rubber strip; putting the conductive rubber strip into glycerol at 160 ℃ for vulcanization for 20min, taking out, cleaning the surface of the conductive rubber strip, and cutting the conductive rubber strip into small sections with the length of 50 mm;
step S5, plating a layer of copper metal thin film with the thickness of 10 microns on the surface of the small section prepared in the step S4 by using a magnetron sputtering method to obtain the piezoresistive wire;
step S6, preparing the flexible packaging layer, the flexible cavity layer and the flexible substrate layer through a mold injection molding process, uniformly mixing Sylgard184 PDMS prepolymer and a curing agent according to the mass ratio of 10:1, vacuumizing to remove air bubbles, injecting into an aluminum alloy mold, placing in a thermostat at 80 ℃ for 3 hours, and then peeling off from the mold; wherein the thickness of the flexible packaging layer and the flexible substrate layer is 25 μm;
step S7, performing oxygen plasma activation on the lower surface of the flexible cavity layer and the upper surface of the flexible substrate layer, and aligning and attaching;
step S8, performing oxygen plasma activation on the upper surface of the first flexible cavity layer, the side surface tangent to the first through hole and the side surface of the first through hole, and attaching the piezoelectric wire to the middle position of the upper surface of the first flexible cavity layer through the first through hole; similarly, oxygen plasma activation is carried out on the upper surface of the second flexible cavity layer, the side surface tangent to the second through hole and the side surface of the second through hole, and the piezoresistive threads penetrate through the second through hole and are attached to the middle position of the upper surface of the second flexible cavity layer;
step S9, a layer of UV hardening resin is coated on the lower surface of the flexible packaging layer prepared in the step S6 in a spinning mode, and the UV hardening resin and the component prepared in the step S8 are placed in silicone oil liquid; aligning the lower surface of the flexible packaging layer with the upper surface of the flexible substrate layer, and irradiating UV hardening resin by using ultraviolet light with the wavelength of 365nm to enable the UV hardening resin to be attached, taken out and subjected to surface cleaning to prepare the sensitive unit;
s10, coating KE12 polyurethane formic ether on the surface of a finger mould, and preparing a bionic fingerprint with the width of 0.2mm and the thickness of 0.2 mm; putting the mould into a vacuum drying box, and starting a vacuum air exhaust device to remove bubbles; then taking out the die, curing for 3 hours at room temperature, embedding the sensitive units prepared in the step S9 into the bionic fingerprint according to a certain arrangement sequence, and curing for 2 hours at room temperature to prepare the piezoelectric piezoresistive sensitive array;
step S11, evenly injecting KE12 polyurethane into the finger mold; placing the mold into a vacuum drying oven, removing bubbles, taking out, standing at room temperature for 5 hours for curing, and then stripping the mold;
step S12, cutting the piezoelectric wires and the piezoresistive wires exposed outside the finger-shaped substrate into the same length, and immersing the piezoelectric wires in DMF solution to dissolve the PVDF piezoelectric layer and expose a conductive core with the length of 2 mm; immersing the piezoresistive threads into No. 92 gasoline for 2mm, swelling the conductive rubber layer, and removing the conductive rubber layer by using a scraper to expose a conductive core with 2 mm; and cleaning the exposed surface of the tungsten filament to obtain the human-simulated tactile finger body.
The invention has the beneficial effects that:
1. the mechanical stimulation perception corpuscle in the finger tip of a human body is selected as a bionic object, and the piezoelectric wire simulates the meissner corpuscle and the annular corpuscle, so that the measurement of dynamic force is realized; the piezoresistive wire simulates a Lafenib corpuscle and a Merkel touch pad to realize the measurement of static force, thereby realizing the function of the composite measurement of dynamic and static force and having good comprehensive performance.
2. The design of introducing the bionic fingerprint on the surface of the finger improves the sensitivity of the piezoelectric piezoresistive sensitive array, embeds the sensitive array below the bionic fingerprint, has the spatial resolution of 1mm, and improves the higher-level touch perception capability of shape recognition and the like of an object.
3. The flexible packaging outer layer and the flexible substrate layer are aligned and attached in the silicone oil liquid, so that the flexible packaging outer layer and the flexible substrate layer can be guaranteed to be filled with liquid and free of bubbles, and the response capability of the sensitive unit to external force is improved.
4. The silicon oil is used as a pressure transmission medium, and has stable chemical and physical properties, so that the internal pressure is uniformly distributed.
5. The flexible packaging layer, the flexible cavity layer and the flexible substrate layer are all made of flexible materials, silicone oil can be deformed at will, the structure of the sensitive unit is compact, curved surface loading is facilitated, and the problem that the conventional rigid touch sensor is difficult to load on the surface of an artificial hand, the fingers of a robot and the curved surface of a body can be solved.
Drawings
FIG. 1 is a split perspective view of a layered structure of a humanoid tactile finger of the present invention;
FIG. 2 is a partial enlarged view of a bionic fingerprint according to the present invention;
FIG. 3 is a cross-sectional view of a sensing unit of the present invention;
FIG. 4 is a layered exploded view of a sensing unit of the present invention;
FIG. 5 is a perspective view of a flexible packaging layer of the present invention;
FIG. 6 is a perspective view of another perspective of the flexible packaging layer of the present invention;
FIG. 7 is a cross-sectional view of a flexible cavity layer of the present invention;
FIG. 8 is a top view of the assembly of the flexible cavity layer and the flexible substrate layer of the present invention;
FIG. 9 is an assembled top view of the piezoelectric thread, piezoresistive thread and flexible cavity layer of the present invention;
FIG. 10 is a view of the end of the piezoelectric wire of the present invention;
FIG. 11 is a view of the end structure of a piezoresistive thread of the present invention.
In the figure: 1. bionic fingerprints; 2. a piezoelectric piezoresistive sensitive array; 3. a finger shaped base; 4. a flexible encapsulation layer; 5. a silicone oil liquid layer; 6. a piezoelectric wire; 7. a piezoresistive wire; 8. a flexible cavity layer; 8a, a first flexible cavity layer, 8b and a second flexible cavity layer; 9. a flexible substrate layer; 10a, a first through hole; 10b, a second through hole; 11. a first tungsten wire; 12. a PVDF piezoelectric layer; 13. a first copper-plated conductive layer; 14. a second tungsten wire; 15. a conductive rubber layer; 16. a second copper-plated conductive layer.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The embodiment discloses a piezoelectric piezoresistive composite humanoid tactile finger which comprises a humanoid tactile finger body;
as shown in the attached figure 1, the layered structure is a split three-dimensional view, a human-simulated tactile finger body is similar to a far knuckle of a human thumb, and the human-simulated tactile finger body sequentially consists of a bionic fingerprint 1, a piezoelectric piezoresistive sensitive array 2 and a finger-shaped substrate 3 from top to bottom; the local amplification structure of the bionic fingerprint 1 is shown in figure 2, the bionic fingerprint 1 is spiral, the width and the height are both 0.2mm, and the distance between the fingerprints is 0.5mm-1.0 mm.
The piezoelectric piezoresistive sensitive array 2 consists of 531 sensitive units, is embedded right below the bionic fingerprint 1, has the spatial resolution of 1mm and the integral distribution area of 426mm2. As shown in fig. 3 and 4, each sensing unit comprises a flexible packaging layer 4 and a flexible substrate layer 9, and a sealed cavity is formed between the flexible packaging layer and the flexible substrate layer, and a silicone oil liquid layer 5 is filled in the sealed cavity to serve as a hydraulic pressure conducting medium; silicon oil liquidPiezoelectric wires 6 and piezoresistive wires 7 are arranged in the body layer 5, and the piezoelectric wires 6 and the piezoresistive wires 7 penetrate through the flexible substrate layer 9 and extend to the outside of the finger-shaped substrate 3 so as to be connected with external electrode leads; flexible cavity layers 8 are arranged between the piezoelectric wires 6 and the flexible substrate layer 9 and between the piezoresistive wires 7 and the flexible substrate layer 9 (for convenience of distinction, the two flexible cavity layers 8 are respectively marked as a first flexible cavity layer 8a and a second flexible cavity layer 8 b).
The flexible packaging layer 4 is a hollow hemisphere with a radius of 0.25mm, the spherical surface thickness is 25 μm, and the three-dimensional structure is shown in fig. 5 and 6. The flexible substrate layer 9 is an axisymmetric structure, has a radius of 0.25mm and a thickness of 25 μm, and is provided with two through holes (for convenience of distinction, the two through holes are respectively marked as a first through hole 10a and a second through hole 10b) having a radius of 32 μm, and the distance between the centers of the two through holes is 324 μm. The cross-section of the flexible cavity layer 8 is shown in fig. 7, and its overall size is 100 μm × 100 μm × 50 μm, and its lower surface has a rectangular parallelepiped cavity of 80 μm × 80 μm × 40 μm to provide a deformation space for the piezoelectric wire 6 and the piezoresistive wire 7 when they are stressed.
As shown in fig. 3 and 8, the lower surface of the flexible cavity layer 8 is fixed on the flexible substrate layer 9, and the side surface is tangent to the through hole. As shown in fig. 3 and 9, the piezoelectric wire 6 and the piezoresistive wire 7 are mounted at the middle of the flexible cavity layer 8 by oxygen plasma activation, and connected to the external electrode lead through two through holes against the side of the flexible cavity layer 8. After the piezoelectric wire 6, the piezoresistive wire 7, the flexible cavity layer 8 and the flexible substrate layer 9 are assembled, the flexible cavity layer and the flexible packaging layer 4 are immersed into silicon oil liquid together for final packaging of the sensitive unit, so that the silicon oil liquid layer 5 can be filled with a hydraulic pressure transmission medium and is free of bubbles, and a good sealing effect is achieved.
As shown in fig. 3 and 10, the piezoelectric wire 6 is composed of a first tungsten wire 11 with a radius of 15 μm, a PVDF piezoelectric layer 12 with a thickness of 7 μm, and a first copper-plated conductive layer 13 with a thickness of 10 μm in this order from the inside to the outside, and has an approximately zigzag structure with a 2 mm-long exposed first tungsten wire 11 at the end. The exposed first tungsten wire 11 and the first copper-plated conductive layer 13 are connected to external electrode leads, respectively.
As shown in fig. 3 and 11, the piezoresistive wire 7 is composed of a second tungsten wire 14, a conductive rubber layer 15 and a second copper-plated conductive layer 16, the second tungsten wire 14 has a radius of 15 μm, a thickness of 7 μm for the conductive rubber layer 15 and a thickness of 10 μm for the second copper-plated conductive layer 16, and has an overall approximate C-shaped structure with a 2 mm-long exposed second tungsten wire 14 at the end. The external electrode leads are connected to the exposed second tungsten wire 14 and the second copper-plated conductive layer 16, respectively.
The flexible encapsulation layer 4, the flexible cavity layer 8 and the flexible substrate layer 9 are all molded from PDMS material by casting.
The working principle of the piezoelectric piezoresistive composite humanoid tactile finger is as follows: when the surface of the human-simulated touch finger body is acted by external force, the bionic fingerprint 1 transmits the external force to the piezoelectric piezoresistive sensitive array 3. The silicon oil liquid 5 in each sensitive unit is used as a hydraulic pressure transmission medium, so that the pressure is uniformly transmitted to the piezoelectric wire 6 and the piezoresistive wire 7. The flexible cavity layer 8 provides a deformable space for the piezo-electric wires 6 and piezo-resistive wires 7 to be stressed. When external force is sensed by the piezoelectric wire 6, charges are generated on the upper surface and the lower surface of the PVDF piezoelectric layer 12, the first tungsten wire 11 and the first copper-plated conductive layer 13 are respectively connected with external electrode leads, and the dynamic force of the surface of the human-simulated finger is measured by detecting the amount of the charges. When the piezoresistive wire 7 senses an external force transmitted by the conductive liquid oil, the internal resistivity of the piezoresistive wire is changed, the second tungsten wire 14 and the second copper-plated conductive layer 16 are respectively connected with the external electrode lead, and the static force on the surface of the human-simulated finger is measured by detecting the change of the resistivity, so that the function of composite measurement of the dynamic force and the static force is realized.
The embodiment also discloses a preparation method of the piezoelectric piezoresistive composite humanoid tactile finger, which comprises the following steps:
step S1, putting PVDF particles into a constant-temperature stainless steel container at 80 ℃ for 1 hour, stirring once every 5 minutes, and then melting in a constant-temperature furnace at 180 ℃; putting the molten PVDF into a hopper of an extruder, enabling a tungsten wire with the length of 30m and the diameter of 0.03mm to pass through a metal pipe, enabling the temperature of the hopper and a neck mold to be constant at 180 ℃, enabling the rotation speed of a screw to be 10r/min, extruding the tungsten wire through a circular neck mold with the radius of 22 mu m, shaping the tungsten wire through a double-roller open mill, cooling the tungsten wire to obtain the tungsten wire with the PVDF wrapped on the surface, and cutting the tungsten wire into small sections with the length of 50 mm.
Step S2, laying the small segments cut in the step S1 on a clamp, and installing the small segments on the clampLoading copper with the purity of 99.99 percent on a rotating drum of a multi-target magnetron sputtering coating machine; pumping the air pressure in the vacuum chamber to 5 × 10-3Pa, introducing argon gas of sputtering gas with the purity of 99.99 percent, and passing 50mA direct current between the cathode and the anode to obtain the piezoelectric wire 6 with the surface covered with the copper metal coating, wherein the thickness of the piezoelectric wire is 10 mu m.
Step S3, immersing the piezoelectric wire 6 prepared in the step S2 in a DMF solution for 2mm to dissolve the PVDF piezoelectric layer, exposing a conductive core with the length of 2mm, and then polarizing the piezoelectric wire 6 by utilizing piezoelectric fiber polarizing equipment; immersing a piezoelectric wire 6 in methyl silicone oil, wherein a tungsten wire is used as an anode, and a copper-plated conductive layer is used as a cathode; polarizing at 70 ℃ and 1000V for 60min, and taking out after methyl silicone oil is cooled to room temperature.
Step S4, preparing conductive rubber, wherein the raw materials are carbon black, silicon rubber, petroleum ether and nano SiO2The silane coupling agent, dibutyltin dilaurate and vulcanizing agent ethyl orthosilicate in a ratio of 2.5: 10: 6: 2: 0.3: 0.3: 0.7; diluting silicon rubber and petroleum ether in proportion, and then sequentially adding carbon black and SiO2Stirring the silane coupling agent and the dibutyltin dilaurate for 5min to uniformly mix the components, adding ethyl orthosilicate, continuously stirring the mixture for 5min, and vacuumizing the mixed solution to prepare a conductive rubber mixed solution; pouring the mixed solution into a hopper of an extruder, enabling a tungsten wire with the length of 30m and the diameter of 0.03mm to pass through a metal tube, keeping the temperature of the hopper and an opening die at 50 ℃, enabling the rotation speed of a screw to be 60r/min, extruding through a circular opening die with the radius of 22 mu m, and collecting the prepared conductive rubber strip; putting the conductive rubber strip into glycerol at 160 ℃ for vulcanizing for 20min, taking out, cleaning the surface, and cutting into small sections with the length of 50 mm.
And step S5, plating a layer of copper metal thin film with the thickness of 10 microns on the surface of the small section prepared in the step S4 by using a magnetron sputtering method to obtain the piezoresistive thread 7.
Step S6, preparing the flexible packaging layer 4, the flexible cavity layer 8 and the flexible substrate layer 9 through a mold injection molding process, uniformly mixing Sylgard184 PDMS prepolymer and a curing agent according to the mass ratio of 10:1, vacuumizing to remove bubbles, injecting into an aluminum alloy mold, placing in a thermostat at 80 ℃ for 3 hours, and then peeling off the mold; wherein the thickness of the flexible encapsulation layer 4 and the flexible substrate layer 9 is 25 μm.
Step S7, oxygen plasma activation is performed on the lower surface of the flexible cavity layer 8 and the upper surface of the flexible substrate layer 9, and alignment and bonding are performed.
Step S8, performing oxygen plasma activation on the upper surface of the first flexible cavity layer 8a, the side surface tangent to the first through hole 10a and the side surface of the first through hole 10a, and attaching the piezoelectric wire 6 to the middle position of the upper surface of the first flexible cavity layer 8a through the first through hole 10 a; and similarly, oxygen plasma activation is carried out on the upper surface of the second flexible cavity layer 8b, the side surface tangent to the second through hole 10b and the side surface of the second through hole 10b, and the piezoresistive thread 7 penetrates through the second through hole 10b and is attached to the middle position of the upper surface of the second flexible cavity layer 8 b.
Step S9, spin-coating a layer of UV hardening resin on the lower surface of the flexible encapsulation layer 4 prepared in step S6, and placing the UV hardening resin and the component prepared in step S8 in silicone oil liquid; aligning the lower surface of the flexible packaging layer 4 with the upper surface of the flexible substrate layer 9, irradiating the UV hardening resin by using ultraviolet light with the wavelength of 365nm, attaching the UV hardening resin, taking out the UV hardening resin, and cleaning the surface of the UV hardening resin to prepare the sensitive unit.
S10, coating KE12 polyurethane formic ether on the surface of a finger mould, and preparing a bionic fingerprint 1 with the width of 0.2mm and the thickness of 0.2 mm; putting the mould into a vacuum drying box, and starting a vacuum air exhaust device to remove bubbles; and then taking out the die, curing for 3 hours at room temperature, embedding the sensitive units prepared in the step S9 into the bionic fingerprint according to a certain arrangement sequence, and curing for 2 hours at room temperature to prepare the piezoelectric piezoresistive sensitive array 2.
Step S11, evenly injecting KE12 polyurethane into the finger mold; and (3) putting the mould into a vacuum drying oven, removing bubbles, taking out, standing at room temperature for 5 hours for curing treatment, and then stripping the mould.
Step S12, cutting the piezoelectric wires 6 and the piezoresistive wires 7 exposed outside the finger-shaped substrate into the same length, and immersing the piezoelectric wires 6 in a DMF solution to dissolve the PVDF piezoelectric layer to expose a conductive core with the length of 2 mm; immersing the piezoresistive thread 7 in No. 92 gasoline for 2mm, swelling the conductive rubber layer, and removing the conductive rubber layer by using a scraper to expose a conductive core of 2 mm; and cleaning the exposed surface of the tungsten filament to obtain the human-simulated tactile finger body.
According to the steps, the manufactured piezoelectric piezoresistive composite humanoid tactile finger has a good dynamic and static force composite detection function, and can obtain good tactile information feedback no matter instant contact or lasting stress so as to finish accurate identification and stable operation on an object.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

Claims (7)

1. The utility model provides a compound imitative humanoid sense of touch finger of piezoelectricity pressure drag which characterized in that: the bionic human tactile finger comprises a human-simulated tactile finger body, wherein the human-simulated tactile finger body consists of a bionic fingerprint (1), a piezoelectric piezoresistive sensitive array (2) and a finger-shaped substrate (3) from top to bottom in sequence;
the piezoelectric piezoresistive sensitive array (2) is composed of a plurality of sensitive units, each sensitive unit comprises a flexible packaging layer (4) and a flexible substrate layer (9), a sealed cavity is formed between the flexible packaging layer and the flexible substrate layer, and a silicon oil liquid layer (5) is filled in the sealed cavity to serve as a hydraulic pressure conducting medium; the piezoelectric wire (6) and the piezoresistive wire (7) are arranged in the silicone oil liquid layer (5), and both the piezoelectric wire (6) and the piezoresistive wire (7) penetrate through the flexible substrate layer (9) and extend to the outside of the finger-shaped substrate (3) so as to be connected with an external electrode lead; a flexible cavity layer (8) is arranged between the piezoelectric wires (6) and the flexible substrate layer (9) and between the piezoresistive wires (7);
the piezoelectric wire (6) is composed of a first tungsten wire (11), a PVDF piezoelectric layer (12) and a first copper-plated conductive layer (13) from inside to outside in sequence; the piezoresistive wire (7) is composed of a second tungsten wire (14), a conductive rubber layer (15) and a second copper-plated conductive layer (16) from inside to outside in sequence.
2. The piezoelectric piezoresistive composite humanoid tactile finger according to claim 1, characterized in that: the number of the sensitive units on the piezoelectric piezoresistive sensitive array (2) is 531.
3. The piezoelectric piezoresistive composite humanoid tactile finger according to claim 1, characterized in that: the piezoelectric piezoresistive sensitive array (2) is positioned right below the humanoid fingerprint (1), the spatial resolution is 1mm, and the overall distribution area is 426mm2。
4. The piezoelectric piezoresistive composite humanoid tactile finger according to claim 1, characterized in that: the flexible substrate layer (9) is provided with through holes for the piezoelectric wires (6) and the piezoresistive wires (7) to pass through respectively, and the center distance between the two through holes is 324 micrometers.
5. The piezoelectric piezoresistive composite humanoid tactile finger according to claim 1, characterized in that: the piezoelectric wire (6) is of a Z-shaped structure, and the piezoresistive wire (7) is of a C-shaped structure.
6. The piezoelectric piezoresistive composite humanoid tactile finger according to claim 1, characterized in that: the flexible packaging layer (4), the flexible cavity layer (8) and the flexible substrate layer (9) are all molded by PDMS materials through casting, the overall size of the flexible cavity layer (8) is 100 micrometers multiplied by 50 micrometers, and a cuboid cavity of 80 micrometers multiplied by 40 micrometers is formed inside the flexible cavity layer.
7. A preparation method of a piezoelectric piezoresistive composite humanoid tactile finger is characterized by comprising the following steps:
step S1, putting PVDF particles into a constant-temperature stainless steel container at 80 ℃ for 1 hour, stirring once every 5 minutes, and then melting in a constant-temperature furnace at 180 ℃; putting the molten PVDF into a hopper of an extruder, enabling a tungsten wire with the length of 30m and the diameter of 0.03mm to pass through a metal pipe, enabling the temperature of the hopper and a neck mold to be constant at 180 ℃, enabling the rotation speed of a screw to be 10r/min, extruding the tungsten wire through a circular neck mold with the radius of 22 mu m, shaping the tungsten wire through a double-roller open mill, cooling the tungsten wire to obtain the tungsten wire with the PVDF coated on the surface, and cutting the tungsten wire into small sections with the length of 50 mm;
s2, paving the small sections cut in the S1 on a clamp, installing the clamp on a rotary drum of a multi-target magnetron sputtering film plating machine, and installing copper with the purity of 99.99 percent on a cathode target; pumping the air pressure in the vacuum chamber to 5 × 10-3Pa, introducing argon gas which is a sputtering gas with the purity of 99.99 percent, and electrifying 50mA direct current between the cathode and the anode to obtain the piezoelectric wire (6) with the surface covered with the copper metal coating, wherein the thickness of the piezoelectric wire is 10 mu m;
step S3, immersing the piezoelectric wire (6) prepared in the step S2 in a DMF solution for 2mm to dissolve the PVDF piezoelectric layer, exposing a conductive core with the length of 2mm, and then polarizing the piezoelectric wire (6) by utilizing piezoelectric fiber polarizing equipment; immersing a piezoelectric wire (6) into methyl silicone oil, wherein a tungsten wire is used as an anode, and a copper-plated conductive layer is used as a cathode; polarizing at 70 ℃ by applying 1000V voltage for 60min, and taking out after methyl silicone oil is cooled to room temperature;
step S4, preparing conductive rubber, wherein the raw materials are carbon black, silicon rubber, petroleum ether and nano SiO2The silane coupling agent, dibutyltin dilaurate and vulcanizing agent ethyl orthosilicate in a ratio of 2.5: 10: 6: 2: 0.3: 0.3: 0.7; diluting silicon rubber and petroleum ether in proportion, and then sequentially adding carbon black and SiO2Stirring the silane coupling agent and the dibutyltin dilaurate for 5min to uniformly mix the components, adding ethyl orthosilicate, continuously stirring the mixture for 5min, and vacuumizing the mixed solution to prepare a conductive rubber mixed solution; pouring the mixed solution into a hopper of an extruder, enabling a tungsten wire with the length of 30m and the diameter of 0.03mm to pass through a metal tube, keeping the temperature of the hopper and an opening die at 50 ℃, enabling the rotation speed of a screw to be 60r/min, extruding through a circular opening die with the radius of 22 mu m, and collecting the prepared conductive rubber strip; putting the conductive rubber strip into glycerol at 160 ℃ for vulcanization for 20min, taking out, cleaning the surface of the conductive rubber strip, and cutting the conductive rubber strip into small sections with the length of 50 mm;
step S5, plating a layer of copper metal thin film with the thickness of 10 mu m on the surface of the small section prepared in the step S4 by a magnetron sputtering method to obtain a piezoresistive thread (7);
step S6, preparing a flexible packaging layer (4), a flexible cavity layer (8) and a flexible substrate layer (9) through a mold injection molding process, uniformly mixing Sylgard184 PDMS prepolymer and a curing agent according to a mass ratio of 10:1, vacuumizing to remove bubbles, injecting into an aluminum alloy mold, placing in a thermostat at 80 ℃ for 3 hours, and then peeling off from the mold; wherein the thickness of the flexible encapsulation layer (4) and the flexible substrate layer (9) is 25 μm;
step S7, performing oxygen plasma activation on the lower surface of the flexible cavity layer (8) and the upper surface of the flexible substrate layer (9), and aligning and attaching;
step S8, carrying out oxygen plasma activation on the upper surface of the first flexible cavity layer (8 a), the side surface tangent to the first through hole (10 a) and the side surface of the first through hole (10 a), and sticking the piezoelectric wire (6) to the middle position of the upper surface of the first flexible cavity layer (8 a) through the first through hole (10 a); similarly, oxygen plasma activation is carried out on the upper surface of the second flexible cavity layer (8 b), the side surface tangent to the second through hole (10 b) and the side surface of the second through hole (10 b), and the piezoresistive thread (7) penetrates through the second through hole (10 b) and is attached to the middle position of the upper surface of the second flexible cavity layer (8 b);
step S9, spin-coating a layer of UV hardening resin on the lower surface of the flexible packaging layer (4) prepared in step S6, and placing the UV hardening resin and the component prepared in step S8 in silicone oil liquid; aligning the lower surface of the flexible packaging layer (4) with the upper surface of the flexible substrate layer (9), and irradiating UV hardening resin by using ultraviolet light with the wavelength of 365nm to enable the UV hardening resin to be attached, taken out and subjected to surface cleaning to prepare a sensitive unit;
s10, coating KE12 polyurethane formic ether on the surface of a finger mould, and preparing a bionic fingerprint (1) with the width of 0.2mm and the thickness of 0.2 mm; putting the mould into a vacuum drying box, and starting a vacuum air exhaust device to remove bubbles; then taking out the die, curing for 3 hours at room temperature, embedding the sensitive units prepared in the step S9 into the bionic fingerprint according to a certain arrangement sequence, and curing for 2 hours at room temperature to prepare the piezoelectric piezoresistive sensitive array (2);
step S11, evenly injecting KE12 polyurethane into the finger mold; placing the mold into a vacuum drying oven, removing bubbles, taking out, standing at room temperature for 5 hours for curing, and then stripping the mold;
step S12, cutting the piezoelectric wire (6) and the piezoresistive wire (7) exposed out of the finger-shaped substrate into the same length, and immersing the piezoelectric wire (6) into a DMF solution to dissolve the PVDF piezoelectric layer to expose a conductive core with the length of 2 mm; immersing the piezoresistive wire (7) into No. 92 gasoline for 2mm, swelling the conductive rubber layer, and removing the swollen conductive rubber layer by using a scraper to expose a conductive core of 2 mm; and cleaning the exposed surface of the tungsten filament to obtain the human-simulated tactile finger body.
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