CN112179410A - Multifunctional flexible touch sensor and preparation method thereof - Google Patents
Multifunctional flexible touch sensor and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a multifunctional flexible touch sensor and a preparation method thereof. The multifunctional flexible touch sensor with a novel structure is obtained by introducing the elastic layer and the flexible sensing layer and adopting a multi-layer laminating assembly method, wherein the elastic layer is provided with a micro-convex array for conducting mechanical information and a through hole array for conducting temperature information, and the flexible sensing layer comprises a pressure mechanical sensing unit array, a temperature sensing unit array and a flexible insulating substrate with a planar electrode array on the surface. The structure can realize the multifunctional detection of the sensor on the tactile information of pressure, sliding and temperature, and the real-time detection of the sensor on the spatial distribution of the tactile information, and overcomes the defect of single measurement function of a tactile sensing device in the prior art. The sensor can be directly worn at the tail end of the finger of the manipulator and collects the touch information of the manipulator in real time, and has the characteristics of array, multifunction, wearability, low cost and customization.
Description
Technical Field
The invention relates to an electronic solid device and a measuring device for a control system, in particular to a measuring device for a touch perception control system of an intelligent robot.
Background
The flexible sensor plays an important role in the foundation of the internet of things, and the research and the application of the flexible sensor are further promoted by the remarkable progress of the artificial intelligence technology and the micro-nano processing technology. The touch sensor is an important component of the flexible sensor, and the development of the flexible touch sensor has positive effects and influences on the development of the industrial and living fields of intelligent robots, health monitoring, human-computer interaction, electronic skins, consumer electronics and the like. Particularly, the touch sensing is an important link of the robot sensing and control, and the flexible touch sensor with advanced sensing performance and excellent adaptability has great significance for improving the intelligent sensing capability and the smart control capability of the robot system.
In recent years, innovative researches on advanced sensing materials such as graphene, carbon nanotubes, metal nanomaterials, porous nanomaterials, conductive polymers and the like make the sensing capability of the flexible touch sensor break through continuously. Existing flexible tactile sensors have made significant advances in mechanical measurements. However, the touch sensors reported at present rely on complicated manufacturing processes such as micro-nano processing and semiconductor processing, the manufacturing cost of the sensors is high, the degree of customization is low, the sensing function of the touch sensors is single, the detection of various touch information such as pressure, sliding and temperature is difficult to realize at the same time, and the touch sensors having the characteristics of sensing unit array, sensing function diversification and flexible wearable performance are difficult to research. In addition, the practical application of the flexible touch sensor in the robot system still faces technical challenges, the common robot arm often adopts a rigid pressure sensor, so that the robot system lacks a flexible sensing array, and most of the touch sensors are difficult to highly adapt or closely fit with the robot arm with an irregular surface shape, which hinders the integration and application of the touch sensor in the robot arm system. In summary, it is necessary to develop an array, multifunctional, wearable flexible tactile sensor for a robot tactile sensing control system such as a smart manipulator, and to implement low-cost and customizable manufacturing.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a novel multifunctional flexible touch sensor and a preparation method thereof, and solves the problem that the touch sensor in the prior art is single in measurement function.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the multifunctional flexible touch sensor comprises an elastic layer and a flexible sensing layer which are combined together, wherein the surface of the elastic layer is provided with a micro-protrusion array, the elastic layer is provided with a through hole array, the flexible sensing layer comprises a flexible insulating substrate, a mechanical sensing unit array, a temperature sensing unit array and a planar electrode array, the mechanical sensing unit array, the temperature sensing unit array and the planar electrode array are positioned between the elastic layer and the flexible insulating substrate, the planar electrode array is arranged on the flexible insulating substrate, and each temperature sensing unit and each mechanical sensing unit are respectively communicated with an external circuit through a pair of planar electrodes, the micro-bulges are distributed right above each mechanical sensing unit so that the micro-bulges can conduct pressure and sliding information to the mechanical sensing unit, and each through hole is right opposite to one temperature sensing unit and can conduct temperature information to the temperature sensing unit.
Furthermore, the size of the bottom surface of each micro-bump is micron-sized, and the distance between two adjacent micro-bumps is more than 0 and less than or equal to 1000 μm.
Furthermore, the elastic heat-conducting gasket is arranged in the through hole of the elastic layer, and the elastic heat-conducting gasket is attached to the surface of the temperature sensing unit opposite to the through hole.
Furthermore, the elastic heat conduction gasket covers the temperature sensing unit attached to the elastic heat conduction gasket.
Furthermore, the thickness of the elastic heat conduction gasket is larger than or equal to that of the through hole.
Furthermore, the invention also comprises an elastic finger sleeve, and the flexible sensing layer is fixed with the elastic finger sleeve.
Further, the elastic layer is an elastic resin layer.
The preparation method of the multifunctional flexible touch sensor comprises the following steps: manufacturing a planar electrode array on the surface of the flexible insulating substrate by adopting a printing electronic process; manufacturing a mechanical sensing unit array and a temperature sensing unit array on the surface of a flexible insulating substrate with a planar electrode array by adopting a printing electronic process, and connecting each temperature sensing unit and each mechanical sensing unit with a pair of planar electrodes to obtain a flexible sensing layer; manufacturing an elastic resin layer with a micro-protrusion array and a through hole array by adopting an additive manufacturing process; and laminating and assembling the elastic resin layer and the flexible sensing layer by adopting uncured elastic resin liquid, wherein the material of the elastic resin liquid is the same as that of the elastic resin layer, and curing is carried out to obtain the multifunctional flexible touch sensor, wherein the micro-protrusions are distributed right above each mechanical sensing unit, each through hole is right opposite to one temperature sensing unit, and the elastic heat-conducting gasket attached to each temperature sensing unit is arranged in the corresponding through hole.
Compared with the prior art, the invention has the following advantages:
(1) the flexible touch sensor with a novel structure is obtained by introducing the elastic layer and the flexible sensing layer and adopting a sensor assembling method of multilayer lamination, wherein the elastic layer is provided with a micro-convex array for conducting mechanical information and a through hole array for conducting temperature information, the flexible sensing layer comprises a pressure mechanical sensing unit, a temperature sensing unit and a flexible insulating substrate, the surface of the flexible insulating substrate is provided with a planar electrode, and each sensing unit is arranged in an array and is positioned between the elastic layer and the flexible insulating substrate. The structure can improve the detection sensitivity of the sensor to pressure, sliding and temperature, and enhance the real-time detection capability of the sensor to the space distribution of the touch information, thereby realizing the multifunctional detection of the sensor to the touch information of pressure, sliding and temperature, and overcoming the defect of single measurement function of a touch sensing device in the prior art.
(2) When the elastic layer is made of elastic resin, the elastic resin layer and the flexible sensing layer are bonded together by using elastic resin liquid which is made of the same material as the elastic layer, so that the tight combination degree of all layers of the sensor can be improved, the assembly process of the sensor is simplified, the mechanical strength of the flexible sensor is enhanced, and the sensing performance of the flexible sensor is improved.
(3) The preparation method of the multifunctional flexible touch sensor is compatible with a printing electronic process, a precision cutting process and an additive manufacturing process, can reduce the processing and manufacturing cost of devices, improves the customization degree of the processing and manufacturing of the devices, and increases the design and development flexibility of the devices.
(4) According to the multifunctional flexible touch sensor, the flexible sensing material, the multilayer fit assembly structure, the wearable elastic finger sleeve design and the elastic microstructure design are adopted, so that the high flexibility and the high reliability of the sensor are ensured, the adaptability of the sensor to a complex surface is improved, and the sensor is favorable for being effectively integrated and stably used as wearable equipment in robot control systems such as an intelligent manipulator and the like.
(5) The preparation of the flexible wearable touch sensor with the characteristics of sensing unit array, sensing function diversification and flexibility is difficult in the prior art, but the multifunctional flexible touch sensor disclosed by the invention overcomes the difficulty, and has the characteristics of sensing unit array, sensing function diversification and flexibility and wearability.
Drawings
FIG. 1 is an exploded view of a multi-functional flexible tactile sensor according to the present invention;
FIG. 2 is a perspective view of FIG. 1;
FIG. 3 is a microscope image of the upper surface (partial) of the elastomeric layer of FIG. 1, which can be seen to have an array of microprotrusions on its upper surface;
fig. 4 is a distribution diagram of the mechanical sensing unit array and the temperature sensing unit array in fig. 1.
Fig. 5 is a schematic layout of the planar electrode array on the surface of the flexible insulating substrate of fig. 1, which shows the alignment of each pair of planar electrodes with each sensing unit including a mechanical sensing unit and a temperature sensing unit, wherein the positions of the mechanical sensing unit and the temperature sensing unit are shown by dotted lines.
Fig. 6 is a schematic view of the elastic layer of fig. 1.
In the figure, 1, an elastic layer, 2, an elastic heat conduction gasket, 3, a flexible sensing layer, 4, an elastic finger sleeve, 11, a micro-bulge, 12, a through hole, 31, a flexible insulating substrate, 32, a planar electrode, 33, a mechanical sensing unit and 34, a temperature sensing unit.
Detailed Description
The invention is described in detail below with reference to the figures and specific examples.
Referring to fig. 1 and 2, unlike the existing sensor, the present invention is characterized in that the tactile sensor comprises a multi-layer structure including an elastic layer 1 and a flexible sensing layer 3, the layers are effectively assembled by means of bonding to combine the layers together, a micro-protrusion array for conducting mechanical information and a through hole array for conducting temperature information are arranged on the elastic layer 1, a mechanical sensing unit 33, a temperature sensing unit 34 and a flexible insulating substrate 31 with a surface provided with a planar electrode 32 are introduced into the flexible sensing layer 3, the micro-protrusion array corresponds to the mechanical sensing unit 33, and the through hole array corresponds to the temperature sensing unit 34, thereby realizing the multifunctional detection of the tactile information of pressure, sliding and temperature by the sensor of the present invention. The mechanical sensing units 33 and the temperature sensing units 34 in the flexible sensing layer 3 are arranged in an array, so that the array of the sensing units is realized. The invention realizes the wearable integration of the sensor at the tail end of the mechanical finger by adopting a flexible structure design and introducing the elastic finger sleeve 4.
As shown in fig. 1, 2 and 3, the upper surface of the elastic layer 1 has an array of micro-protrusions. Each of the microprotrusions 11 may be integrally formed with the elastic layer 1. The micro-protrusions 11 may transmit pressure and sliding information of an object (hereinafter, referred to as a "contacted object") contacting the micro-protrusions 11 to the mechanical sensing unit. The shape of the bottom surface of each of the microprotrusions 11 is not particularly limited in the present invention, and may preferably be a regular shape such as a circle, a triangle, a rectangle, or a regular polygon. Similarly, each of the microprotrusions 11 may preferably be cylindrical, pyramidal, or the like in its entirety. In the example shown in fig. 2 and 3, the base of the microprotrusions 11 are square in shape and the overall structure is pyramidal. In a preferred embodiment of the present invention, the size of the bottom surface of the micro-protrusion 11 is in the micrometer range to meet the detection requirement for the low pressure signal and the sliding signal. For example, the size of the bottom surface of each micro-protrusion 11 is in the range of 0 to 1000 μm, and preferably, the size of the bottom surface of the micro-protrusion 11 is in the range of 100 to 1000 μm. In one embodiment of the present invention, the distance between every two adjacent micro-protrusions 11 is greater than 0 and not greater than 1000 μm, and preferably, the distance between every two adjacent micro-protrusions 11 is 100 to 1000 μm.
As shown in fig. 1 and 2, the elastic layer 1 has an array of through holes, and each through hole 12 penetrates through the entire elastic layer 1 from top to bottom. The through-hole 12 may conduct heat of a contacted object in contact with the elastic layer 1 to the temperature sensing unit. The shape of the through-hole 12 is not particularly limited in the present invention, but may preferably be a regular shape such as a circle or a square. In the example of fig. 2, the through-hole 12 is circular in cross section. As a preferred embodiment of the present invention, the diameter of the cross section of the through hole 12 is in millimeter order to better meet the detection requirement for the temperature signal. Preferably, the diameter of the cross section of each through hole 12 is larger than 0 and less than or equal to 10 mm, and the size of the bottom surface of the micro-protrusion 11 is in the range of 1-10 mm.
As a preferred embodiment of the present invention, the elastic layer 1 is an elastic resin layer, and the material thereof may be a curable elastic resin material, such as a photo-curable elastic resin. The manufacturing process of the elastic layer 1 may use an additive manufacturing process such as Stereolithography (SLA) three-dimensional printing or Digital Light Projection (DLP) three-dimensional printing.
As shown in fig. 1, 2, 4 and 5, the flexible sensing layer 3 comprises a flexible insulating substrate 31, a mechanical sensing unit 33, a temperature sensing unit 34 and an array of planar electrodes 32, wherein the mechanical sensing unit 33 and the temperature sensing unit 34 of the flexible sensing layer 3 are located between the elastic layer 1 and the flexible insulating substrate 31 of the flexible sensing layer 3. An array of planar electrodes 32 is provided on a flexible insulating substrate 31. The mechanical sensing unit 33 can be a conductive pressure-sensitive material thin layer or a conductive pressure-sensitive material pattern, and the temperature sensing unit 34 can be a conductive temperature-sensitive material thin layer or a conductive temperature-sensitive material pattern. As shown in fig. 2 and 5, each of the mechanical sensing units 33 and each of the temperature sensing units 34 are respectively in effective contact with and electrically connected to the pair of planar electrodes 32, so that each of the sensing units is electrically connected to an external circuit through the pair of planar electrodes 32, so as to measure the resistance change of each of the sensing units in real time. Since each mechanical sensing unit 33 and each temperature sensing unit 34 work independently, and all the planar electrodes 32 are in the same plane, the signal crosstalk between the sensing units is effectively reduced. Furthermore, all the mechanical sensing units 33 and the temperature sensing units 34 form a sensing array, so that the array arrangement of the sensing units is realized, and the spatial distribution of the tactile information can be effectively detected. Preferably, the mechanical sensing units 33 and the temperature sensing units 34 are distributed in a p × q array, p > 1, and q > 1. Preferably, the mechanical sensing unit 33 is square in shape, and the temperature sensing unit 34 is circular in shape.
As shown in fig. 1 and fig. 2, when the elastic layer 1 and the flexible sensing layer 3 are designed, one or more micro-protrusions are distributed right above each mechanical sensing unit 33, so that pressure and sliding information of a contacted object is transmitted to the mechanical sensing unit 33 through the micro-protrusion array. In addition, each through hole 12 is arranged to face one temperature sensing unit 34, so that the temperature information of the contacted object is conducted to each temperature sensing unit 34 through each through hole array. Preferably, the size of the temperature sensing unit 34 of the flexible sensing layer 3 is slightly smaller than the size of the through hole 12 of the elastic layer 1.
As shown in fig. 1, 2 and 5, when the elastic layer 1 and the flexible sensing layer 3 are assembled, the mechanical sensing unit 33 and the temperature sensing unit 34 are firstly manufactured on the surface of the flexible insulating substrate 31 with the planar electrode 32 on the upper surface to form the flexible sensing layer 3, and then the lower surface of the elastic layer 1 and the upper surface of the flexible sensing layer 3 are flatly attached and bonded together, so that the mechanical sensing unit array, the temperature sensing unit array and the planar electrode array are positioned between the elastic layer 1 and the flexible insulating substrate 31, and the elastic layer 1 and the flexible sensing layer 3 are combined together to realize the multi-layer assembly of the sensor. When the elastic layer 1 and the flexible sensing layer 3 are attached, one or a plurality of micro-protrusions are distributed right above each mechanical sensing unit 33, and each through hole 12 is aligned with one temperature sensing unit 34 right below the through hole.
Referring to fig. 1 and 2, as a preferred embodiment of the present invention, the flexible sensing layer 3 may further include an elastic thermal pad 2, and the elastic thermal pad 2 is adhered to a surface of the temperature sensing unit 34 of the flexible sensing layer 3. The size of the elastic heat conducting pad 2 is preferably smaller than or equal to the size of the through hole 12 of the elastic layer 1 and larger than or equal to the size of the temperature sensing unit 34 directly below the elastic layer, and the thickness of the elastic heat conducting pad 2 is preferably larger than or equal to the thickness of the through hole 12 of the elastic layer 1, so that the elastic heat conducting pad 2 can cover the temperature sensing unit directly below the elastic layer and the elastic heat conducting pad 2 can be placed in the through hole 12. Preferably, the size of the elastic heat conducting pad 2 is slightly smaller than that of the through hole 12, and the thickness of the elastic heat conducting pad 2 is the same as that of the through hole 12. When the elastic heat conduction gasket 2 is adhered to the temperature sensing unit 34 of the flexible sensing layer 3, the area where the elastic heat conduction gasket 2 is located is preferably covered with the area where the temperature sensing unit 34 is located. When the elastic layer 1 and the flexible sensing layer 3 adhered with the elastic heat conduction gasket 2 are assembled, the elastic heat conduction gasket 2 preferably penetrates through the through hole 12 of the elastic layer 1, so that the elastic heat conduction gasket 2 effectively conducts the temperature information of the contacted object to the temperature sensing unit 34.
As an embodiment of the present invention, referring to fig. 1, the lower surface of the flexible sensing layer 3 may be fixed on the outer surface of the elastic finger stall 4, and when fixing, the lower surface of the flexible sensing layer 3 and the outer surface of the elastic finger stall 4 are preferably attached and fixed together, so that the multifunctional flexible tactile sensor of the present invention may be directly worn at the end of a finger of a manipulator, and applied as a wearable measuring device in a robot control system such as a smart manipulator, etc., to acquire tactile information such as pressure, sliding, and temperature of the manipulator in real time during operation, and output signals in the form of electrical signals.
In the present invention, the material of the mechanical sensing unit 33 may be a composite material having conductive and pressure-sensitive characteristics prepared by a solution method, a melt method, or an electrospinning method, such as a mixture of one of Thermoplastic Polyurethane (TPU), silicone rubber, an elastic resin, Polydimethylsiloxane (PDMS) and one or more of carbon nanotubes, graphene, polyaniline rods, inorganic nanoparticles, inorganic nanowires, and inorganic nanosheets. The material of the temperature sensing unit 34 may be a composite material having conductive and temperature-sensitive characteristics prepared by a solution method, a melting method, or an electrospinning method, such as a mixture of poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid (PEDOT/PSS) and carbon nanotubes. The manufacturing process of the mechanical sensing unit 33 and the temperature sensing unit 34 may be a printed electronic process, such as screen printing, dispensing printing, inkjet printing, or direct-write printing. The material of the planar electrode 32 may preferably be a conductive material that can be formulated into a printing ink, such as one of metal nanoparticles, metal nanowires, conductive pastes. The planar electrode 32 may be fabricated by a printed electronic process such as screen printing, dispensing printing, ink jet printing, or direct write printing. The material of the flexible insulating substrate 31 may be a flexible insulating plastic, such as one of Polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and parylene. The manufacturing process of the flexible insulating substrate 31 may be a precision cutting technique, such as laser cutting or mechanical cutting. The material of the elastic heat-conducting pad 2 may be a flexible heat-conducting composite material with certain heat conductivity and flexibility, such as one of heat-conducting silica gel, heat-conducting carbon fiber, and heat-conducting gel. The material of the elastic finger stall 4 can be an elastic polymer material, such as one of silicone rubber, natural rubber, nitrile rubber, Thermoplastic Polyurethane (TPU), and polyolefin elastomer (POE).
The following describes in detail a method for manufacturing a multifunctional flexible tactile sensor according to the present invention, with a specific embodiment, specifically including:
(1) cutting manufacturing of the flexible insulating substrate 31: the polyimide film substrate (i.e., the flexible insulating substrate 31) was cut in a previously designed shape using a mechanical cutter, the selected polyimide film substrate had a thickness of 50 μm, and the designed polyimide film substrate had a rectangular shape of 2.5 cm × 4.0 cm. After the polyimide film substrate is cut, the surface of the polyimide film substrate is cleaned by ethanol and deionized water respectively, and then the polyimide film substrate is heated for 10 min at the temperature of 100 ℃. This step results in a flexible insulating substrate 31 of a specific shape.
(2) Inkjet printing fabrication of planar electrode arrays: the ink-jet printing of the planar electrode array was performed on the upper surface of the polyimide film substrate (i.e., the flexible insulating substrate 31) using an ink-jet printer, using silver nanoparticle conductive ink (an aqueous solution of silver nanoparticles with a mass fraction of 20%) in accordance with a pattern of a mechanical sensing cell array and a temperature sensing cell array (see fig. 4) designed in advance. The minimum line width of each planar electrode 32 is 0.2 mm. Each pair of planar electrodes may be connected to an external circuit through a flexible printed circuit board (FPC interface). And heating the planar electrode array for 30 min at 150 ℃ after completing the ink-jet printing to solidify the planar electrode array and form a continuous structure. This step results in a flexible insulating substrate 31 with a planar electrode array printed on the upper surface.
(3) Dispensing, printing and manufacturing of the mechanical sensing unit array and the temperature sensing unit array: mixing 8% of isopropanol dispersion liquid of the multi-walled carbon nanotube and photocuring elastic resin according to the mass ratio of 2: 1 for 30 min and carrying out ultrasonic treatment for 60 min, and then stirring and heating the mixed solution at 50 ℃ for 60 min to remove isopropanol to obtain the pressure-sensitive sensing ink. Subsequently, an aqueous solution of poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid (PEDOT/PSS) at a mass fraction of 2% and an aqueous dispersion of multiwalled carbon nanotubes at a mass fraction of 8% were mixed as follows: 1 for 30 min and carrying out ultrasonic treatment for 60 min to obtain the temperature-sensitive sensing ink. Subsequently, the pressure-sensitive sensing ink and the temperature-sensitive sensing ink are respectively subjected to dispensing printing of the mechanical sensing units 33 and the temperature sensing units 34 on the upper surface of the flexible insulating substrate 31 with the planar electrode array obtained in the step (2) according to a pre-designed pattern (shown in fig. 5) by using a dispensing printer, wherein the mechanical sensing units 33 are square with the side length equal to 3 cm and are arranged in an array of 3 × 3, the temperature sensing units 34 are round with the diameter equal to 3 cm and are arranged in an array of 2 × 2. Each sensing cell is in contact with and conductive with a corresponding pair of planar electrodes 32. After the dispensing printing is finished, the sensing units are kept for 20min under the conditions of 405 nm blue-violet light illumination and 60 ℃ heating, so that the mechanical sensing unit 33 and the temperature sensing unit 34 are solidified and form a continuous structure. This step results in a flexible insulating substrate 31 with an array of mechanical sensing elements, an array of temperature sensing elements and an array of planar electrodes.
(4) Assembling the elastic heat-conducting gasket 2: and cutting the single-sided viscous heat-conducting silica gel gasket (namely the elastic heat-conducting gasket 2) according to a pre-designed shape by using a mechanical cutting machine, wherein the thickness of the selected heat-conducting silica gel gasket is 1.0 mm, and the designed shape of the heat-conducting silica gel gasket is a circle with the diameter equal to 3 mm. After the cutting of the heat-conducting silica gel pads is completed, adhering the sticky surface of each heat-conducting silica gel pad to the surface of the corresponding temperature sensing unit 34 obtained in the step (3), so that each heat-conducting silica gel pad covers the temperature sensing unit 34 positioned right below the heat-conducting silica gel pad. And finally, obtaining the flexible sensing layer 3 which is adhered with the heat-conducting silica gel gasket on the surface and comprises a mechanical sensing unit array, a temperature sensing unit array, a planar electrode array and a flexible insulating substrate 31.
(5) Additive manufacturing of the elastic layer 1: an elastic layer 1 having a microprotrusion array and a through hole array was three-dimensionally printed with a photocurable elastic resin in a pre-designed configuration (shown in fig. 2, 3 and 6) using a three-dimensional printer having a stereolithography function (SLA), the elastic layer 1 had a size of 2.5 cm × 2.5 cm and a thickness of 1.0 mm, each microprotrusion 11 had a height of 0.5 mm, a bottom surface shape of a square with a side length of 0.5 mm, an overall structure of a regular pyramid, a pitch between adjacent microprotrusions 11 of 0.5 mm, each through hole 12 had a circular shape with a diameter of 3.2 mm, the through holes 12 penetrated through the entire elastic layer 1, and a pitch between adjacent through holes 12 of 5.8 mm. After the elastic layer 1 was printed, it was washed with isopropyl alcohol and then completely cured by exposure to 405 nm of blue-violet light and heating at 60 ℃ for 20 min. This step finally results in an elastic layer 1 with an array of microprotrusions and an array of through holes.
(6) Multi-layer assembly of a multifunctional flexible tactile sensor: and (3) coating a layer of uncured light-cured elastic resin liquid on the lower surface of the elastic layer 1 (which is a light-cured elastic resin layer) obtained in the step (5) in a blade mode, wherein the material of the light-cured elastic resin liquid is the same as that of the elastic layer 1. Then, the lower surface of the elastic layer 1 is aligned with and bonded to the upper surface of the flexible sensing layer 3 having the heat conductive silicone gasket adhered to the surface thereof obtained in the step (4) (see fig. 1, 2, and 4), and since the micro-protrusions 11 of the elastic layer 1 correspond to the positions of the mechanical sensing units 33 of the flexible sensing layer 3, the through holes 12 of the elastic layer 1 correspond to the positions of the temperature sensing units 34 of the flexible sensing layer 3, and the heat conductive silicone gasket covers the temperature sensing units 34, the area where the micro-protrusions 11 are located covers the area where the mechanical sensing units 33 are located, the area where the through holes 12 are located covers the area where the temperature sensing units 34 are located, and the heat conductive silicone gasket is placed in the through holes 12. And then, keeping the elastic layer 1 and the flexible sensing layer 3 with the heat-conducting silica gel gasket adhered on the surface under the illumination of 405 nm blue-violet light and the heating condition of 60 ℃ for 20min until the photo-cured elastic resin liquid is completely cured, and tightly combining and fixing the elastic layer 1 and the flexible sensing layer 3 together in the process. Finally, the assembly of the multilayer structure including the elastic layer 1, the heat-conducting silica gel gasket, the mechanical sensing unit array, the temperature sensing unit array, the planar electrode array and the flexible insulating substrate 31 is realized, and the multifunctional flexible touch sensor is obtained.
(7) Further, the multifunctional flexible touch sensor obtained in the step (6) may be adhered to the outer surface of the elastic finger sleeve 4 by room temperature curing silicone rubber, so as to obtain another multifunctional flexible touch sensor of the present invention. The touch sensor can be directly worn at the tail end of a finger of a Robotiq manipulator, collects touch information such as pressure, sliding and temperature of the manipulator in the operation process in real time, and outputs signals in the form of electric signals. In addition, the sensor has the characteristics of being arrayed, multifunctional, wearable, low in cost and customizable, and can solve the problems that in the prior art, a touch sensing device is complex in manufacturing process, low in customization degree, single in measurement function and difficult to effectively adapt and integrate with a robot control system.
The use method and the working process of the multifunctional flexible touch sensor are as follows:
when the multifunctional flexible touch sensor is applied with a touch signal, the elastic layer 1 is provided with the surface micro-protrusion array, the micro-protrusions 11 are suitable for being provided with smaller elastic modulus (typical value is 3.2 MPa) and easy to generate mechanical deformation, the structural characteristics and the mechanical characteristics of the micro-protrusion array can improve the sensitivity of the sensor for detecting mechanical signals, meanwhile, the elastic layer 1 is provided with the through hole array, the elastic heat conduction gasket 2 can be arranged in the through hole 12 for heat conduction, the structural characteristics and the thermal characteristics of the through hole array can improve the sensitivity of the sensor for detecting temperature signals, and therefore the elastic layer 1 with the micro-protrusion array and the through hole array can effectively conduct pressure signals, sliding signals and temperature signals to the sensing units corresponding to the flexible sensing layer 3. Preferably, when the elastic layer 1 is made of elastic resin, the elastic resin layer and the flexible sensing layer 3 are bonded together by using elastic resin liquid which is the same as the material of the elastic layer 1, so that the degree of tight combination of all layers of the sensor can be improved, the assembly process of the sensor is simplified, the mechanical strength of the flexible sensor is enhanced, and the sensing performance of the flexible sensor is improved. The flexible sensing layer 3 includes mechanical sensing units 33 and temperature sensing units 34, each mechanical sensing unit 33 can convert a pressure signal into a resistance value of the mechanical sensing unit 33 (the magnitude of pressure affects the resistance value of a resistor), each sliding signal can convert a sliding signal into a resistance value change of the mechanical sensing unit 33 (the sliding speed of a contacted object and the sliding friction affect the time domain and frequency domain characteristics of the resistance value change), each temperature sensing unit 34 can convert a temperature signal into a resistance value of the temperature sensing unit 34 (the magnitude of temperature affects the resistance value of the resistor), and thus the mechanical sensing unit 33 and the temperature sensing unit 34 can effectively detect the pressure signal, the sliding signal and the temperature signal. In addition, the mechanical sensing units 33 and the temperature sensing units 34 in the flexible sensing layer 3 are arranged in an array, so that the array of the sensing units is realized, the sensing unit array formed by the mechanical sensing units 33 and the temperature sensing units 34 can effectively detect pressure distribution and temperature distribution, the resistance value of each mechanical sensing unit 33 reflects the pressure acting on the area corresponding to the mechanical sensing unit 33, and the resistance value of each temperature sensing unit 34 reflects the temperature acting on the area corresponding to the temperature sensing unit 34. Each sensing unit in the flexible sensing layer 3 is connected with a corresponding pair of planar electrodes 32 on the surface of the flexible insulating substrate 31, each sensing unit works independently, and all the planar electrodes 32 are located on the same plane, so that signal crosstalk between the sensing units is effectively reduced, and the anti-interference capability and the sensitivity of the sensor are improved. Further, when the sensing unit array manufactured by the manufacturing method of the present invention is adopted, since the sensing unit array is directly printed and cured on the surface of the flexible insulating substrate 31 having the planar electrode 32, a high bonding strength between the sensing unit array and the flexible insulating substrate 31 is ensured, and a reliable electrical connection between the sensing unit array and the planar electrode 32 is ensured, thereby improving the mechanical flexibility and the electrical stability of the sensor. Each of the planar electrodes 32 may be connected to an external measuring circuit, so that the external measuring circuit can obtain tactile information of pressure, slip, and temperature acting on the surface of the sensor by measuring and analyzing the magnitude of resistance and the change in resistance of the sensing unit array in real time. In addition, the sensor can be worn at the tail end of fingers of mechanical arms with different shapes through the elastic finger sleeves 4, and can be used as a measuring device of a robot control system to provide tactile information.
Claims (10)
1. A multifunctional flexible tactile sensor, characterized by: the temperature sensing device comprises an elastic layer and a flexible sensing layer which are combined together, wherein a micro-protrusion array is arranged on the surface of the elastic layer, the elastic layer is provided with a through hole array, the flexible sensing layer comprises a flexible insulating substrate, a mechanical sensing unit array, a temperature sensing unit array and a planar electrode array, the mechanical sensing unit array, the temperature sensing unit array and the planar electrode array are located between the elastic layer and the flexible insulating substrate, the planar electrode array is arranged on the flexible insulating substrate, each temperature sensing unit and each mechanical sensing unit are respectively communicated with an external circuit through a pair of planar electrodes, micro protrusions are distributed right above each mechanical sensing unit so that the micro protrusions can conduct pressure and sliding information to the mechanical sensing unit, and each through hole is right opposite to one temperature sensing unit and can conduct temperature information to the temperature sensing unit.
2. The multifunctional flexible tactile sensor according to claim 1, wherein: the size of the bottom surface of each micro-bump is micron-sized, and the distance between every two adjacent micro-bumps is larger than 0 and less than or equal to 1000 microns.
3. The multifunctional flexible tactile sensor according to claim 1 or 2, wherein: an elastic heat conduction gasket is arranged in the through hole of the elastic layer, and the elastic heat conduction gasket is attached to the surface of the temperature sensing unit opposite to the through hole.
4. The multifunctional flexible tactile sensor according to claim 3, wherein: the elastic heat conduction gasket covers the temperature sensing unit attached to the elastic heat conduction gasket.
5. The multifunctional flexible tactile sensor according to claim 3, wherein: the thickness of the elastic heat conduction gasket is larger than or equal to that of the through hole.
6. The multifunctional flexible tactile sensor according to claim 4, wherein: the thickness of the elastic heat conduction gasket is larger than or equal to that of the through hole.
7. The multifunctional flexible tactile sensor according to claim 1, 2, 4, 5 or 6, wherein: the flexible sensing device further comprises an elastic finger sleeve, and the flexible sensing layer is fixed with the elastic finger sleeve.
8. The multifunctional flexible tactile sensor according to claim 1, 2, 4, 5 or 6, wherein: the elastic layer is an elastic resin layer.
9. The multi-functional flexible tactile sensor according to claim 7, wherein: the elastic layer is an elastic resin layer.
10. A method of making the multifunctional flexible tactile sensor of claim 1 or 2, comprising:
manufacturing a planar electrode array on the surface of the flexible insulating substrate by adopting a printing electronic process; manufacturing a mechanical sensing unit array and a temperature sensing unit array on the surface of a flexible insulating substrate with a planar electrode array by adopting a printing electronic process, and connecting each temperature sensing unit and each mechanical sensing unit with a pair of planar electrodes to obtain a flexible sensing layer; manufacturing an elastic resin layer with a micro-protrusion array and a through hole array by adopting an additive manufacturing process; and laminating and assembling the elastic resin layer and the flexible sensing layer by adopting uncured elastic resin liquid, wherein the material of the elastic resin liquid is the same as that of the elastic resin layer, and curing is carried out to obtain the multifunctional flexible touch sensor, wherein the micro-protrusions are distributed right above each mechanical sensing unit, each through hole is right opposite to one temperature sensing unit, and the elastic heat-conducting gasket attached to each temperature sensing unit is arranged in the corresponding through hole.
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