CN113970391A

CN113970391A - Robot electronic skin based on capacitance and friction power generation principle and preparation method thereof

Info

Publication number: CN113970391A
Application number: CN202111111575.7A
Authority: CN
Inventors: 杨剑乐; 魏兴浩; 王添涛; 杨少鹏
Original assignee: Shaanxi Zhongjian Jianle Intelligent Robot Co ltd
Current assignee: Shaanxi Zhongjian Jianle Intelligent Robot Co ltd
Priority date: 2021-09-23
Filing date: 2021-09-23
Publication date: 2022-01-25

Abstract

The invention discloses a robot electronic skin based on a capacitance and friction power generation principle, which is mainly formed by sequentially and tightly assembling a flexible abrasive paper modified layer, an upper substrate layer, an upper electrode layer, a lower substrate layer and a lower electrode layer from top to bottom.

Description

Robot electronic skin based on capacitance and friction power generation principle and preparation method thereof

Technical Field

The invention relates to the technical field of robot electronic skin touch sensing, in particular to a robot electronic skin based on a capacitance and friction power generation principle and a preparation method thereof.

Background

The service robot is gradually entering into the production and life of people, and plays an increasingly important role in the development of the human society. The collaborative robot application design specification ISO TS 15066 shows that the closer the human-computer interaction, the higher the design requirements. Frequent and complex human-computer interaction scenes put higher-level requirements on the perception function of the robot. Bionics is a research hotspot in the field of robotics. Tactile perception and temperature perception are basic means for adapting organisms to environmental changes. Haptics in the conventional sense include the perception of variables such as pressure, shear force, texture, etc. The tactile sensor can assist the service robot to complete expected actions in an unstructured environment and perform safe human-robot interaction. The temperature sensor can identify a heat source and a cold source in the environment, so that the robot can distinguish people from objects in the environment to carry out targeted interaction. The touch perception and the temperature perception of the simulation organism, and the proximity sensor is integrated in the skin of the robot, so that the robot can identify the whole process from the approach to the contact of an external object with the body, further can be competent for more complex working scenes, and is also beneficial to ensuring the intrinsic safety in the human-computer interaction process.

The development direction of the next stage of the robot is man-machine integration and harmonious phase. In order to realize man-machine integration, the safety problem of the robot needs to be solved, and an important requirement is that the robot needs to have certain environmental perception capability, such as vision, touch and the like. Currently, the research on machine vision is more intensive, but the research on the touch sense of the robot is less, and therefore, the need for more economical and practical robot skin to adapt to the coming of the man-machine integration era is urgent.

The current general technology only provides a common solution for preventing robot collision, such as the solution proposed in document CN201310365565 that uses robot joint torque to identify whether collision occurs; document CN201310365565 mentions that a viscoelastic cushion layer is wrapped on the robot body and one or more tactile sensors are attached to achieve the function of collision prevention. A typical disadvantage of these solutions is that the specific location of the collision cannot be identified. Document CN201610029884 proposes to measure the pressure of each part through hydraulic pressure, but the sensor used in the document consists of a metal base and a cavity filled with hydraulic oil, so that the load of the robot is increased and the tension cannot be sensed. Another technical route is electronic skin based on IT technology and composite materials, described in the literature "electronic skin technology and ITs patent analysis", which is capable of sensing pressure and shear forces. However, this technique is expensive, is easily damaged, and is difficult to be applied in the industry.

Disclosure of Invention

The invention aims to design a robot electronic skin based on a capacitance and friction power generation principle, which is a flexible device capable of covering the surface of a robot to be used as the electronic skin to endow the electronic skin with touch perception capability, so that the robot can also perceive touch, and the robot electronic skin has wide application prospect.

Therefore, the technical scheme adopted by the invention is as follows: a robot electronic skin based on a capacitance and friction power generation principle is mainly formed by tightly assembling a flexible abrasive paper modified layer, an upper substrate layer, an upper electrode layer, a lower substrate layer and a lower electrode layer from top to bottom in sequence, wherein the area of the upper electrode layer is larger than that of the lower electrode layer;

the upper basal layer and the lower basal layer of the electronic skin are made of flexible stretchable materials;

the upper electrode layer and the lower electrode layer adopt liquid gallium indium tin alloy;

when the sand paper modified layer is prepared, a PDMS material needs to be coated on the surface of the sand paper in a spinning mode, then heating and curing are carried out, and then a PDMS film is peeled from the surface of the sand paper, so that the sand paper modified layer is obtained;

the upper base layer, the sand paper modification layer and the lower base layer are arranged in a micron hole array structure.

The upper base layer further comprises a plurality of planar electrodes, and the planar electrodes are arranged on the upper electrode layer between the arrangement surfaces of the upper base layer and the lower base layer.

The invention also discloses a manufacturing method of the robot electronic skin based on the capacitance and friction power generation principle, which comprises the following steps:

the method comprises the following steps: the preparation method of the electrode layer comprising the upper electrode layer and the lower electrode layer comprises the following steps:

(1) taking a clean 2-inch silicon wafer, firstly washing the silicon wafer with isopropanol, then washing with deionized water, and finally drying the silicon wafer by blowing, wherein the cleaning process of the silicon wafer can be completed by circulating for about three times;

(2) spin-coating a PVA solution with the mass fraction of 10% on the surface of a silicon wafer at the speed of 500rpm for 40s, then heating the silicon wafer coated with the PVA solution on a hot plate at the temperature of 90 ℃ for 10 minutes, and curing the PVA solution to form a film;

(3) preparing a PDMS solution, wherein the mass ratio of the prepolymer to the curing agent is 10:1, stirring for 5 minutes to ensure that the prepolymer and the curing agent are fully mixed, vacuumizing for 30 minutes to eliminate bubbles to complete preparation of PDMS, spin-coating the PDMS solution for 40 seconds, and heating and curing the PDMS after the spin-coating is completed, wherein the heating temperature is 90 ℃ and the heating time is 20 minutes;

4) adhering a cut mask with electrode patterns to a cured PDMS film, wherein the diameter of an upper electrode is 8mm, the diameter of a lower electrode is 5mm, the line width is 0.4mm, the side length of a square connected with an external lead is 1mm, then respectively sputtering a layer of chromium with the thickness of 10nm and a layer of gold film with the thickness of 100nm on the surface of the PDMS film as electrode patterns of a sensor, wherein the chromium is used as an adhesion layer between the gold film and the PDMS to increase the adhesion of gold to the PDMS film, and after the sputtering is finished, peeling the mask from the surface of the PDMS film to finish the preparation of the gold electrode;

5) adhering a 0.4mm copper wire on the surface of a gold electrode by using conductive silver paste, and then putting the gold electrode on a hot plate to be heated and evaporated to remove water in the conductive silver paste, wherein the heating temperature is 90 ℃, and the heating time is 40min, so that the connection between an external wire and the gold electrode is completed;

(6) filling gallium alloy in a glove box with oxygen content less than or equal to 2ppm, putting the silicon wafer subjected to the process in a transition cavity of the glove box to finish three times of vacuumizing and inflating processes to prevent oxygen in the external environment from entering the glove box, then dripping the gallium alloy on the surface of a gold electrode to ensure that the gallium alloy completely covers the gold electrode, keeping the edge of the silicon wafer to slowly rotate in the process, ensuring that liquid metal completely covers the part of a wire outside the gold electrode, and finishing the filling of the liquid metal;

(7) taking the silicon wafer filled with the liquid metal out of the glove box, spin-coating a layer of PDMS on the surface of the gallium alloy to serve as a packaging layer, wherein the spin-coating speed is 1000rpm, the spin-coating time is 40s, then placing the silicon wafer on a hot plate, heating and curing the silicon wafer at 90 ℃ for 20 minutes, and curing the PDMS to form a film so as to finish packaging the liquid metal;

(8) putting the packaged silicon wafer of the liquid metal into a crystallizing dish filled with deionized water, and heating in a water bath to dissolve the PVA layer which is spin-coated in advance, so that the electrode layer which completes the packaging of the liquid metal can be separated from the surface of the silicon wafer, wherein the water bath heating temperature is 90 ℃, and the heating time is about 8 hours, so as to obtain a prepared electrode layer;

step two: the preparation method of the middle dielectric layer comprises a flexible sand paper modified layer, an upper substrate layer and a lower substrate layer, and comprises the following steps:

(1) taking a clean 2-inch silicon wafer, washing the silicon wafer for 3 times by using acetone, and drying the silicon wafer by using nitrogen;

(2) directly inverting the SU82050 photoresist on the surface of the silicon wafer to ensure that the photoresist is completely covered on the surface of the silicon wafer, and then standing the photoresist for about 15 minutes to eliminate bubbles generated in the inversion process of the photoresist;

(3) performing multi-step spin coating of SU82050 photoresist to obtain a required film thickness, firstly placing a silicon wafer on a spin coater sucker, ensuring that the center of the silicon wafer is aligned with the center of the sucker as much as possible, then performing multi-step spin coating at the spin coating speed of 500rpm for 30s, ensuring that the photoresist completely covers the surface of the silicon wafer, and then standing for 15 minutes to eliminate ripples and internal stress generated by the photoresist in the spin coating process;

(4) pre-baking, namely firstly heating the silicon wafer from room temperature to 45 ℃, then heating the silicon wafer from 45 ℃ to 95 ℃ by taking 10 ℃ as a gradient, keeping the temperature at 65 ℃ and 95 ℃ for 3 minutes and 9 minutes respectively to finish the heating process of the pre-baking, and then turning off a hot plate to naturally cool the silicon wafer to room temperature along with the hot plate;

(5) ultraviolet exposure, namely performing ultraviolet exposure under a prepared mask pattern, wherein the subject adopts a contact exposure technology, the photoetching power is 15mW/m2, and the exposure time is set to be 15 s;

(6) post-baking to accelerate the generation of a micron hole pattern in the photoresist, firstly heating the photoresist to 45 ℃ from room temperature, then heating the photoresist to 95 ℃ from 45 ℃ by taking 10 ℃ as a gradient, wherein the temperature is kept at 65 ℃ and 95 ℃ for 2 minutes and 7 minutes respectively, and then turning off a hot plate to naturally cool the silicon wafer to room temperature along with the hot plate;

(7) developing to obtain a required pattern, developing for about 6 minutes in a developing solution special for SU8 photoresist, cleaning floating glue on the surface of the silicon wafer with absolute ethyl alcohol, drying with nitrogen, observing whether the micron hole array structure is clear and complete under a microscope with a super depth of field, and continuing developing until the photoresist is completely removed from the surface of the silicon wafer if the photoresist remains, wherein the thickness of the photoresist film is about 70 mu m;

(8) hard baking, namely heating the silicon wafer from room temperature to 45 ℃, then heating the silicon wafer by taking 10 ℃ as a gradient, heating the silicon wafer from 45 ℃ to 200 ℃, keeping the temperature at 200 ℃ for 30 minutes to fully evaporate the solvent in the photoresist, and naturally cooling the silicon wafer to room temperature along with a hot plate after the hard baking heating process is finished;

(9) preparing a hydrophobic solution, preparing 50mL of hydrophobic solution from ethanol and trichlorosilane according to the volume ratio of 1:1000, stirring for 5 minutes by using a magnetic stirrer to ensure that the ethanol and the trichlorosilane are fully and uniformly mixed, then soaking the silicon wafer subjected to photoetching in the solution for about 1 hour, and performing a hydrophobic treatment process to facilitate stripping of PDMS from the surface of the photoresist;

(10) the method comprises the following steps of firstly, inverting PDMS (polydimethylsiloxane) to form a micro-column array structure, inverting a PDMS solution on the surface of a photoresist, slowly rotating the edge of a silicon wafer to ensure that the PDMS completely covers the surface of the silicon wafer, then placing the silicon wafer in a drying oven for vacuumizing and standing for 2 hours to ensure that the PDMS solution completely enters the bottom of the micro-pore array structure, simultaneously eliminating residual air between the PDMS and the bottom of the micro-pore, heating and curing, wherein the heating temperature is 100 ℃, the heating time is 15 minutes, and finally stripping a cured PDMS film from the surface of the photoresist to finish the preparation of the micro-column structure on the surface of the PDMS film;

(11) taking a silicon wafer as a substrate, pasting a PDMS film on the surface of the silicon wafer, spin-coating a layer of PDMS solution on the surface of a cleaned 2-inch silicon wafer at a spin-coating speed of 1000 r/min for 40s, pasting the back of the PDMS film with a micro-cylinder array structure on the surface of the PDMS solution, then heating the silicon wafer on a hot plate at a heating temperature of 100 ℃ for 15 min, and finishing the pasting of the PDMS film and the silicon wafer;

(12) in order to promote the hydrophobic reaction process, performing reactive ion etching on the PDMS film, wherein the oxygen flow is 20sccm, the reaction pressure is 70Pa, the radio frequency power is 90w, and the reaction time is 90s, and then placing the PDMS film in a prepared hydrophobic solution for hydrophobic treatment, wherein the specific operation process is the same as the step (9);

(13) and secondly, performing secondary mold inversion on PDMS to complete the preparation of the micro-pore array structure, spin-coating a layer of PDMS solution on the surface of a PDMS film with a micro-column structure, wherein the spin-coating speed is 500rpm and the time is 120s, then horizontally standing the silicon wafer for about 2 hours to ensure that the PDMS completely enters the bottom of a gap between the micro-columns, then placing the silicon wafer on a hot plate for heating and curing, the heating temperature is 90 ℃, the heating time is 20 minutes, then continuously spin-coating a layer of PDMS solution on the surface of the cured PDMS film to ensure that the PDMS completely covers the micro-column structure, then performing heating and curing, wherein the curing parameters are the same as those of the first layer of PDMS film, and finally peeling off the PDMS film from the surface of the PDMS film with the micro-column structure to complete the preparation of the PDMS film with the micro-pore structure.

According to the invention, the abrasive paper modified layer enhances the friction force, covers the upper basal layer, improves the sensitivity of the sensor for pressure measurement in a friction power generation sensing mode, and increases the friction effect of the sensor by designing an abrasive paper structure on the surface; in order to increase the sensitivity of the sensor for pressure measurements in the capacitive mode. The robot electronic skin prepared by the invention has good flexibility and higher critical tensile strain and critical compressive strain. The robot electronic skin prepared by the invention has ultrahigh sensitivity to micro-pressure, low detection limit and short response time.

Drawings

Fig. 1 is a schematic view of a robot electronic skin structure based on the principles of capacitance and friction power generation.

Detailed Description

In order to make the technical solutions of the present invention better understood and implemented by those skilled in the art, the present invention is further described below with reference to the following specific embodiments and the accompanying drawings, but the embodiments are not meant to limit the present invention.

As shown in fig. 1, the robot electronic skin based on the capacitance and friction power generation principle is mainly formed by sequentially and tightly assembling a flexible sand paper modified layer 1, an upper substrate layer 2, an upper electrode layer 3, a lower substrate layer 4 and a lower electrode layer 5 from top to bottom, wherein the area of the upper electrode layer is larger than that of the lower electrode layer;

The specific manufacturing method comprises the following steps:

Claims

1. A robot electronic skin based on a capacitance and friction power generation principle is characterized by mainly comprising a flexible abrasive paper modified layer, an upper substrate layer, an upper electrode layer, a lower substrate layer and a lower electrode layer which are tightly assembled from top to bottom in sequence, wherein the area of the upper electrode layer is larger than that of the lower electrode layer;

2. The robot electronic skin based on the capacitance and friction power generation principle as claimed in claim 1, wherein said upper base layer further comprises a plurality of planar electrodes on the upper electrode layer between the arrangement surfaces of the upper base layer and the lower base layer.

3. A method for manufacturing a robot electronic skin based on the capacitance and friction power generation principle according to claim 1, which comprises the following steps: