Flexible tactile sensor and manufacturing method thereof

Abstract

The invention relates to a flexible tactile sensor and a manufacturing method thereof. The first flexible tactile sensor comprises a flexible substrate, a temperature sensing layer, an insulating layer, a stress layer, a lower structure layer, a strain gauge layer, a wire layer, an upper structure layer and a packaging layer. The upper structure layer and the lower structure layer wrap the wire layer and the strain gauge layer to form a four-layer structure; the stress layer is located below the lower structural layer or above the upper structural layer and drives the four-layer structure to be curled to form a three-dimensional structure; the packaging layer wraps the planar structure and the three-dimensional structure and is connected to the flexible substrate. In the second flexible tactile sensor, the upper structure layer and the lower structure layer wrap the row selection wire layer, the insulating layer, the strain gauge layer and the column selection wire layer to form a six-layer structure, and the stress layer drives the six-layer structure to be curled to form a three-dimensional structure. The flexible touch sensor is completely compatible with an existing microelectronic processing technology, low-cost and batch parallel production is allowed, and the flexible touch sensor with the space density and the array shape capable of being customized according to needs is achieved.

Description

Technical Field

[0001] The present invention relates to the fields of sensors and electronic skin, and particularly to a flexible tactile sensor and a manufacturing method thereof. Background Art

[0002] At present, the field of robotics is developing rapidly and plays an important role in industrial automation, human-computer interaction and other fields. The diversification of the motion and perception capabilities of robots is a key goal pursued by researchers. Touch is an important way for humans to perceive and interact with the external environment, and it can help humans obtain the physical characteristics of the external environment. Endowing robots with human-like tactile perception capabilities is crucial for information acquisition and processing in application scenarios such as fine operation, assisted medical treatment, and human-computer interaction. Small, accurate, and customizable tactile sensors provide a basis for expanding the perception capabilities of robots and improving the control accuracy of robots.

[0003] Currently, the existing tactile sensors have at least the following disadvantages: First, tactile information usually includes three components: normal pressure, shear force, and temperature. The existing tactile sensors usually have the ability to perceive one or two of these parameters, but do not have the ability to decouple the three. Second, the existing tactile sensors are usually difficult to be integrated with mature circuit technologies (such as FPC, commercial chips, etc.), which limits the convenience of their data processing and practical applications. Finally, the existing tactile sensors usually can only achieve single-point tactile perception and are difficult to perform large-area tactile monitoring in a customizable array shape. Summary of the Invention

[0004] The present invention provides a flexible tactile sensor and a manufacturing method thereof to overcome the disadvantages of the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The first type of flexible tactile sensor includes a flexible substrate, a temperature sensing layer, an insulating layer, a stress layer, a lower structure layer, a strain gauge layer, a wire layer, an upper structure layer, and a packaging layer; wherein the flexible substrate, the temperature sensing layer, and the insulating layer are arranged in sequence from bottom to top, and the lower structure layer, the strain gauge layer, the wire layer, and the upper structure layer are arranged in sequence from bottom to top; the upper structure layer and the lower structure layer wrap the wire layer and the strain gauge layer to form a four-layer structure; the stress layer is located below the lower structure layer or above the upper structure layer, and the stress layer drives the four-layer structure to curl to form a three-dimensional structure; the flexible substrate, the temperature sensing layer, and the insulating layer are in a planar structure and are located directly below the three-dimensional structure; the insulating layer is used to separate the temperature sensing layer from other conductive components to improve its stability; the packaging layer wraps the above planar structure and three-dimensional structure and is connected to the flexible substrate.

[0007] The second type of flexible tactile sensor includes a flexible substrate, a stress layer, a lower structural layer, a row selection wire layer, an insulating layer, a strain gauge layer, a column selection wire layer, an upper structural layer, and a packaging layer; wherein the lower structural layer, the row selection wire layer, the insulating layer, the strain gauge layer, the column selection wire layer, and the upper structural layer are arranged in sequence from bottom to top, and the upper structural layer and the lower structural layer wrap the row selection wire layer, the insulating layer, the strain gauge layer, and the column selection wire layer to form a six-layer structure; the stress layer is located below the lower structural layer or above the upper structural layer, and the stress layer drives the six-layer structure to curl to form a three-dimensional structure; through holes are left on the insulating layer for the connection of the row selection wire layer and the column selection wire layer at specific positions; the packaging layer wraps the above three-dimensional structure and is connected to the flexible substrate.

[0008] The above-mentioned second tactile sensor can also be added with a temperature sensing layer, that is, a temperature sensing layer and an insulating layer are added between the flexible substrate and the stress layer.

[0009] Preferably, the materials of the flexible substrate, the insulating layer, and the structural layers (the upper structural layer and the lower structural layer) are PI (Polyimide), or PET (Polyethylene terephthalate), or PEN (Polyethylene naphthalate two formic acid glycol ester), or PDMS (Polydimethylsiloxane), or PU (Polyurethane), or parylene, or epoxy resin, or PEDOT:PSS (Poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonate)), or other flexible and biocompatible insulating materials.

[0010] Preferably, the material of the stress layer is SiO 2 , or Si 3 N 4 , or polycrystalline / amorphous silicon, or other materials that generate intrinsic stress during the thin film preparation process. The stress layer can be located below the lower structural layer and drive the four-layer structure to curl through compressive stress, or it can be located above the upper structural layer and drive the four-layer structure to curl through tensile stress.

[0011] Preferably, the materials of the temperature sensing layer, the strain gauge layer, and the wire layer are metal materials, such as Au, Cu, Al, or alloy materials, such as CrNi, CuNi.

[0012] Preferably, the material of the encapsulation layer is a silicone-based material, such as PDMS, Ecoflex, and it is prepared by casting encapsulation. The mold used in the process of casting encapsulation is prepared by 3D printing or CNC machining. The shape of the casting encapsulation is hemispherical, or conical, or pyramid-shaped, or cuboid-shaped, etc., respectively forming a hemispherical encapsulation layer, or a conical encapsulation layer, or a pyramid-shaped encapsulation layer, or a cuboid-shaped encapsulation layer, etc.

[0013] Preferably, the temperature sensing layer and the wire layer are provided with electrodes connected to an external circuit. The functions of the external circuit include crosstalk suppression, channel selection, signal processing, analog-to-digital conversion, wireless data transmission, energy supply, etc. The sensor can be bonded or soldered to a flexible circuit board like a chip and connected to the external circuit through a flexible cable to ensure the flexibility of the sensor part.

[0014] Preferably, the spatial density of the three-dimensional structure can be designed according to the capabilities of micro-nano processing, and has the potential to exceed the density of human finger tactile receptors (>140 per cm 2 ).

[0015] The manufacturing method of the first type of flexible tactile sensor includes the following steps:

[0016] Prepare a flexible substrate on a substrate;

[0017] Sequentially prepare a temperature sensing layer, an insulating layer, a sacrificial layer, a stress layer, a lower structure layer, a strain gauge layer, a wire layer, and an upper structure layer on the flexible substrate;

[0018] Etch away the sacrificial layer by wet etching, so that the stress layer drives the lower structure layer, the strain gauge layer, the wire layer, and the upper structure layer it supports to curl, forming a three-dimensional structure;

[0019] Prepare an encapsulation layer on the three-dimensional structure;

[0020] Detach the flexible substrate from the substrate to obtain a flexible tactile sensor.

[0021] The manufacturing method of the second type of flexible tactile sensor includes the following steps:

[0022] Prepare a flexible substrate on a substrate;

[0023] Sequentially prepare a sacrificial layer, a stress layer, a lower structure layer, a row selection wire layer, an insulating layer, a strain gauge layer, a column selection wire layer, and an upper structure layer on the flexible substrate;

[0024] Etch away the sacrificial layer by wet etching, so that the stress layer drives the lower structure layer, the row selection wire layer, the insulating layer, the strain gauge layer, the column selection wire layer, and the upper structure layer it supports to curl, forming a three-dimensional structure;

[0025] Prepare an encapsulation layer on a three-dimensional structure;

[0026] Detach the flexible substrate from the substrate to obtain a flexible tactile sensor.

[0027] Preferably, the flexible substrate, the lower structural layer, the insulating layer, and the upper structural layer are prepared by spin coating.

[0028] Preferably, the sacrificial layer, the stress layer, the wire layer, the row selection wire layer, the column selection wire layer, and the strain gauge layer are prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0029] Preferably, the material of the sacrificial layer is a metal material such as Al, Mg, Zn, or a polymer material such as PMMA (Polymethyl methacrylate, plexiglass), photoresist.

[0030] Preferably, the preparation process includes a thin film patterning process not mentioned, and the patterning methods include photolithography, lift-off, or etching.

[0031] The first type of flexible tactile sensor of the present invention has the ability to sense multi-modal tactile information such as normal pressure, shear force, and temperature, and is suitable for application scenarios such as pressure ulcer prevention and treatment, bionic touch, etc.; the second type of flexible tactile sensor adopts an array form and mainly senses normal pressure. The sensor has a large spatial density and a high spatial resolution, and is suitable for application scenarios such as robot fine operation and human-computer interaction.

[0032] It can be seen from the technical solutions provided by the present invention above that the processing method of the tactile sensor proposed by the present invention is completely compatible with the existing microelectronic processing technology, allowing low-cost and batch parallel production. And the performance and spatial density of the sensor can be parametrically adjusted according to needs. The tactile sensor is flexible and small in size, and can be pasted or welded on flexible circuit boards of different shapes like a "chip" and used in integration with commercial chips and circuits. Therefore, the present invention truly realizes a flexible tactile sensor with a spatial density and an array shape that can be customized on demand.

[0033] Additional aspects and advantages of the present invention will be given in part in the following description, and these will become obvious from the following description, or can be understood through the practice of the present invention. Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 Schematic diagram of the structure of the first flexible tactile sensor provided by the embodiment of the present invention.

[0036] Figure 2 is Figure 1 Schematic diagram of the shapes of the layers of the first flexible tactile sensor shown in the figure, where (a) is the shape of the flexible substrate, (b) is the shape of the temperature sensing layer, (c) is the shape of the insulating layer, (d) is the shape of the sacrificial layer, (e) is the shape of the stress layer, (f) is the shape of the lower structure layer, (g) is the shape of the wire layer, (h) is the shape of the strain gauge layer, and (i) is the shape of the upper structure layer.

[0037] Figure 3 Microscopic view of the three-dimensional structure of the first flexible tactile sensor provided by the embodiment of the present invention.

[0038] Figure 4 Schematic diagram of the positions of the strain gauges before and after the three-dimensional structure of the first flexible tactile sensor provided by the embodiment of the present invention is tilted, where (a) is before the three-dimensional structure is tilted and (b) is after the three-dimensional structure is tilted.

[0039] Figure 5 Schematic diagram of the working principle of the first flexible tactile sensing provided by the embodiment of the present invention.

[0040] Figure 6 Response of four three-dimensional strain gauges and temperature sensing module in the first flexible tactile sensor provided by the embodiment of the present invention under normal pressure, shear force and temperature excitation.

[0041] Figure 7 Schematic diagram of the structure of the second flexible tactile sensor provided by the embodiment of the present invention.

[0042] Figure 8 Schematic diagram of the shapes of the layers of the second flexible tactile sensor provided by the embodiment of the present invention, where (a) is the shape of the flexible substrate, (b) is the shape of the sacrificial layer, (c) is the shape of the stress layer, (d) is the shape of the lower structure layer, (e) is the shape of the row selection wire layer, (f) is the shape of the insulating layer, (g) is the shape of the column selection wire layer, (h) is the shape of the strain gauge layer, and (i) is the shape of the upper structure layer.

[0043] Figure 9 Microscopic view of the three-dimensional structure of the second flexible tactile sensor provided by the embodiment of the present invention.

[0044] Figure 10 Schematic diagram of the positions of the strain gauges before and after the three-dimensional structure of the second flexible tactile sensor provided by the embodiment of the present invention is tilted, where (a) is before the three-dimensional structure is tilted and (b) is after the three-dimensional structure is tilted.

[0045] Figure 11 Response of the second flexible tactile sensor provided by the embodiment of the present invention under external pressures of different shapes.

[0046] Figure 12 Photo of the arrayed flexible tactile sensor provided by the embodiment of the present invention. Detailed implementation manners

[0047] The following details the implementation manners of the present invention. Examples of the implementation manners are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The implementation manners described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0048] Those skilled in the art of the present technology can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present invention means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or coupling. The phrase "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0049] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here.

[0050] For ease of understanding of the embodiments of the present invention, the following will further explain with specific embodiments as examples in conjunction with the accompanying drawings, and the embodiments do not constitute a limitation to the embodiments of the present invention.

[0051] Embodiment 1

[0052] Figure 1 Schematic structural diagram of the first flexible tactile sensor provided by the embodiment of the present invention. The flexible tactile sensor includes a PI flexible substrate, a Cr / Au temperature sensing layer, a PI insulating layer, an Al sacrificial layer, SiO 2The stress layer, the structure layer under the PI, the NiCr strain gauge layer, the Cr / Au wire layer, the structure layer on the PI, and the PDMS square encapsulation layer. Among them, the structure layer under and on the PI wraps the wire layer and the strain gauge layer to form a four-layer structure. The stress layer supports the four-layer structure. After the sacrificial layer is etched away, the stress layer curls due to the intrinsic stress inside, causing the four-layer structure of the structure layer under, the strain gauge layer, the wire layer, and the structure layer on to curl, forming a three-dimensional structure. The shapes of the layers of the first flexible tactile sensor are as Figure 2 shown.

[0053] The fabrication of the flexible tactile sensor of the present invention is based on micro-nano fabrication processes, which can achieve excellent consistency, stability, and yield. During the fabrication process, the physical properties of the prepared thin films are excellent, and the size, stress, and thickness of the thin films can be flexibly controlled by adjusting various parameters, which makes the fabricated sensors have excellent performance, diverse structures, and good consistency.

[0054] The specific fabrication method of the flexible tactile sensor of the present invention includes the following steps:

[0055] 1) Starting from a clean high-conductive silicon-based substrate, a layer of PI film is spin-coated using a spin coater as a flexible substrate.

[0056] 2) Negative photolithography is performed using a photolithography machine. Subsequently, a layer of Cr film and a layer of Au film are continuously sputtered as a temperature sensing layer using a magnetron sputtering coater. Then, the temperature sensing layer is patterned through a lift-off process.

[0057] 3) A layer of PI film is spin-coated using a spin coater as an insulating layer.

[0058] 4) A layer of Al film is sputtered as a sacrificial layer and a layer of SiO 2 film is sputtered as a stress layer using a magnetron sputtering coater. The intrinsic stress in the stress layer comes from effects such as atomic peening during the magnetron sputtering process. Positive photolithography is performed using a photolithography machine, and the stress layer is patterned using a reactive ion etching machine according to the shape of the strain gauges arranged in the strain gauge layer (such as Figure 2 the cross shape in, or it can also be other shapes). Positive photolithography is performed using a photolithography machine, and the sacrificial layer is patterned using a wet etching method. The stress of the thin film depends on the control of the magnetron sputtering parameters.

[0059] 5) A layer of PI film is spin-coated using a spin coater as the structure layer under. The three-dimensional structure of the sensor depends on the magnitude of the thin film stress, the thickness, and the size of the structure layer.

[0060] 6) Negative photolithography is performed using a photolithography machine. A layer of NiCr alloy film is sputtered as the strain gauge layer using a magnetron sputtering coater, and the strain gauge layer is patterned through a lift-off process.

[0061] 7) Negative photoresist lithography is performed using a lithography machine. A Cr thin film and an Au thin film are continuously sputtered as a wire layer using a magnetron sputtering coater, and the wire layer is patterned using a lift-off process.

[0062] 8) A PI thin film is spin-coated as the upper structure layer using a spin coater. A layer of Al is sputtered as a barrier layer using a magnetron sputtering coater. Positive photoresist lithography is performed using a lithography machine, and the barrier layer is patterned by wet etching. The upper structure layer and the lower structure layer are patterned using a reactive ion etching machine.

[0063] 9) The sacrificial layer and the barrier layer are removed by wet etching. Due to the existence of intrinsic compressive stress in the stress layer, the lower structure layer, the strain gauge layer, the wire layer, and the upper structure layer are driven to curl, forming a three-dimensional structure.

[0064] 10) An aluminum alloy square hollow mold is machined using a CNC lathe. The hollow part of the mold is aligned with the three-dimensional structure, and uncured PDMS is poured into the mold. After the PDMS is cured, the mold is removed to obtain a square package.

[0065] 11) The silicon wafer is electrolyzed with an NaCl solution, and the flexible substrate falls off the silicon wafer, and the flexible tactile sensor is fabricated.

[0066] In this embodiment, the strain gauge layer uses four strain gauges, and four curled three-dimensional structures are encapsulated in a flexible tactile sensor. Figure 3 The three-dimensional structure after the sacrificial layer is etched away. The four strain gauges are arranged in a cross shape, and the temperature sensing module is located directly below the three-dimensional strain gauges and is insulated by a layer of PI. As Figure 4 shown, the four strain gauges have a certain distance in space. When the sacrificial layer is etched, the four strain gauges curl independently, forming four three-dimensional structures. The heights of the four three-dimensional structures after curling are the same, the shapes are the same, and the positions in the package layer are symmetric.

[0067] The strain gauge, as a component with excellent performance stability commonly used in microfabrication, will undergo strain and thus generate a change in resistance when subjected to an external force. Referring to Figure 5 , in the initial state, the four three-dimensional structures have the same shape. When the package layer is subjected to a normal pressure, the four strain gauges are all subjected to the same pressure, undergo tensile strain, and their resistances all increase. Figure 6 The response in (a) of Figure 6In (b), they are the responses of the three-dimensional strain gauge and the planar temperature sensing module respectively when the encapsulation layer is subjected to a normal pressure. When the encapsulation layer is subjected to a horizontal shear force, the strain and resistance changes of the two three-dimensional strain gauges perpendicular to the shear force direction can be ignored. One of the two strain gauges parallel to the shear force direction is subjected to a compressive strain and its resistance decreases; the other is subjected to a tensile strain and its resistance increases. Figure 6 In (c), it is the resistance responses of the four strain gauges when the encapsulation layer is subjected to a horizontal shear force. When the temperature changes, the resistances of both the planar temperature sensing layer and the three-dimensional strain gauge will change. Figure 6 In (d), it is the resistance responses of the planar temperature sensing layer and the three-dimensional strain gauge when the ambient temperature changes. The resistance of the temperature sensing layer is only related to the temperature change and is not affected by the normal pressure and the horizontal shear force. Therefore, it can be used as an accurate temperature sensing unit to calibrate the interference of temperature change on the resistance of the three-dimensional strain gauge.

[0068] The external excitations acting on the flexible tactile sensor are divided into temperature excitation and mechanical excitation, and the temperature excitation and mechanical excitation can be regarded as a linear superposition relationship. The mechanical excitation can be further divided into normal pressure and horizontal shear force, and the two can also be regarded as a linear superposition relationship. Therefore, there are a total of four unknowns for multi-parameter decoupling, including: temperature, the amplitude of the normal pressure in the z-axis direction, the amplitude of the shear force in the x-axis direction, and the amplitude of the horizontal shear force in the y-axis direction. And there are five knowns, including the resistance changes of the four three-dimensional strain gauges and the resistance change of a temperature sensing layer. Since the unknowns can all be regarded as a linear superposition relationship, a linear equation system with four unknowns can be listed. Using the five knowns, the solution of the linear equation system can be easily obtained, and then the multi-parameter decoupling can be realized.

[0069] Embodiment 2

[0070] Figure 7 It is a structural schematic diagram of the second flexible tactile sensor provided in this embodiment. Different from Embodiment 1, the second flexible tactile sensor contains a larger number of three-dimensional strain gauges with the same arrangement direction, forming a three-dimensional strain gauge array with a higher spatial density. The second flexible tactile sensor includes a PI flexible substrate, an Al sacrificial layer, SiO 2 stress layer, a PI lower structural layer, a Cr / Au row selection wire layer, a PI insulating layer, a NiCr strain gauge layer, a Cr / Au column selection wire layer, a PI upper structural layer, and a PDMS square encapsulation layer. Among them, the lower structural layer and the upper structural layer wrap the row selection wire layer, the insulating layer, the strain gauge layer, and the column selection wire layer to form a six-layer structure. The stress layer supports the six-layer structure. After the sacrificial layer is etched away, the stress layer curls due to the intrinsic stress inside, driving the six-layer structure to curl and form a three-dimensional structure. The shapes of the layers of the second flexible tactile sensor are as Figure 8 shown.

[0071] The specific processing method of the second flexible tactile sensor of the present invention includes the following steps:

[0072] 1) Starting from a clean highly conductive silicon-based substrate, spin-coat a layer of PI film using a spin coater as the flexible substrate.

[0073] 2) Sputter a layer of Al film as the sacrificial layer and a layer of SiO 2 film as the stress layer using a magnetron sputtering coater. The intrinsic stress in the stress layer comes from effects such as atomic peening during the magnetron sputtering process. Perform positive photolithography using a photolithography machine, and pattern the stress layer using a reactive ion etching machine according to the shape of the strain gauge arrangement in the strain gauge layer. Perform positive photolithography using a photolithography machine, and pattern the sacrificial layer using a wet etching method. The stress of the film depends on the control of the magnetron sputtering parameters.

[0074] 3) Spin-coat a layer of PI film as the lower structure layer using a spin coater. The three-dimensional structure of the sensor depends on the magnitude of the film stress, the thickness and size of the structure layer. Perform negative photolithography using a photolithography machine, continuously sputter a layer of Cr film and a layer of Au film as the row selection wire layer using a magnetron sputtering coater, and pattern the row selection wire layer through a lift-off process.

[0075] 4) Spin-coat a layer of PI film as the insulating layer using a spin coater, sputter a layer of Al film as the barrier layer using a magnetron sputtering coater, perform positive photolithography using a photolithography machine, pattern the Al barrier layer using wet etching, and pattern the insulating layer using a reactive ion etching machine to form through holes.

[0076] 5) Perform negative photolithography using a photolithography machine, sputter a layer of NiCr alloy film as the strain gauge layer using a magnetron sputtering coater, and pattern the strain gauge layer through a lift-off process.

[0077] 6) Perform negative photolithography using a photolithography machine, continuously sputter a layer of Cr film and a layer of Au film as the column selection wire layer using a magnetron sputtering coater, and pattern the column selection wire layer through a lift-off process.

[0078] 7) Spin-coat a layer of PI film as the upper structure layer using a spin coater. Sputter a layer of Al as the barrier layer using a magnetron sputtering coater, perform positive photolithography using a photolithography machine, pattern the barrier layer using wet etching, and pattern the upper structure layer and the lower structure layer using a reactive ion etching machine.

[0079] 8) Remove the sacrificial layer and the barrier layer using wet etching. Due to the presence of intrinsic compressive stress in the stress layer, drive the lower structure layer, the row selection wire layer, the insulating layer, the strain gauge layer, the column selection wire layer, and the upper structure layer to curl, forming a three-dimensional structure.

[0080] 9) Process the aluminum alloy square hollow mold using a CNC lathe, align the hollow part of the mold with the three-dimensional structure, pour the uncured PMDS into the mold, and remove the mold after the PDMS cures to obtain a square package.

[0081] 10) Electrolyze the silicon wafer with an NaCl solution, and the flexible substrate will peel off from the silicon wafer, completing the preparation of the flexible tactile sensor.

[0082] Figure 9 This is the three-dimensional structure of the second flexible tactile sensor provided in this embodiment after the sacrificial layer is etched away. As Figure 10 shown, there are a total of forty strain gauges in the encapsulation layer, which are spaced apart from each other in space. When the sacrificial layer is etched away, each strain gauge curls independently to form a three-dimensional structure. The height and shape of each three-dimensional structure after curling are the same, but their positions in the encapsulation layer are asymmetric. Among them, the minimum line width of the strain gauge is 12 μm, and the spatial arrangement density is 40 / cm 2 . The 40 three-dimensional strain gauges are arranged in a four-row and ten-column pattern and are connected through four row selection electrodes and ten column selection electrodes. Further, if the minimum line width of the strain gauge layer is reduced to 4.8 μm, a three-dimensional strain gauge spatial density of 360 / cm 2 can be achieved. The second flexible tactile sensor provided in this embodiment has the ability to characterize the normal pressure distribution in a small area. Its principle is similar to that of the flexible tactile sensor in Embodiment 1. When the encapsulation layer is subjected to a normal pressure, the arrayed three-dimensional strain gauges are compressed and strained, resulting in a change in resistance. Since the three-dimensional strain gauges are distributed throughout the encapsulation area and are asymmetric with respect to the position of the normal pressure, different three-dimensional strain gauges respond differently when subjected to a normal pressure. Figure 11 This is the resistance response of the second flexible tactile sensor provided in this embodiment when subjected to normal pressures of different shapes.

[0083] In this embodiment, there are a total of forty strain gauges in the encapsulation layer. In other embodiments, the number of strain gauges can be adjusted according to needs.

[0084] Embodiment 3

[0085] Since the processing techniques in Embodiment 1 and Embodiment 2 can both achieve parallelized mass production, multiple highly consistent flexible tactile sensors can be simultaneously fabricated on the same silicon wafer substrate. Through the encapsulation and substrate peeling methods described in the above embodiments, tactile sensors on a flexible substrate can be obtained. After dicing the tactile sensors on the large-area flexible substrate, small-sized, individually usable flexible tactile sensors can be obtained. By soldering or bonding these flexible tactile sensors onto a flexible circuit board like commercial chips, the result can be as Figure 12The flexible tactile sensor array shown. When combined with the design of the backend circuit, a small-sized and wireless tactile information sensing system can be realized. According to different application requirements, the flexible sensor can be welded or adhered to a flexible circuit board of any shape for use and can be integrated with mature circuit technologies such as commercial chips.

[0086] In summary, the flexible tactile sensor and its manufacturing method proposed by the present invention, compared with the design and implementation schemes of traditional tactile sensors, use a parallelized microelectronic processing technology, have the characteristics of high yield and high consistency, can realize arrayed and batch preparation, have the ability of multi-parameter decoupling and arrayed tactile information distribution perception, and can be conveniently integrated into existing circuits to meet the flexible needs of different application scenarios. The flexible tactile sensor prepared by the present invention is small in size and simple to operate, truly realizing convenient, fast, wearable / skin-attached tactile sensing.

[0087] The manufacturing methods proposed by the present invention all adopt basic laboratory process flows, do not involve high-cost processing technologies, have simple preparation processes, low costs, and short production cycles, and have the possibility of large-scale batch production.

[0088] Those of ordinary skill in the art can understand that the drawings are only schematic diagrams of an embodiment, and the modules or processes in the drawings are not necessarily essential for implementing the present invention.

[0089] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, they are described relatively simply, and the relevant parts can refer to the partial descriptions of the method embodiments. The device and system embodiments described above are only illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement without creative labor.

[0090] As mentioned above, the above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A flexible tactile sensor, characterized in that, it includes a flexible substrate, a temperature sensing layer, an insulating layer, a stress layer, a lower structure layer, a strain gauge layer, a wire layer, an upper structure layer and a packaging layer; wherein the flexible substrate, the temperature sensing layer, and the insulating layer are arranged in sequence from bottom to top, and the lower structure layer, the strain gauge layer, the wire layer, and the upper structure layer are arranged in sequence from bottom to top; the upper structure layer and the lower structure layer wrap the wire layer and the strain gauge layer to form a four-layer structure; the stress layer is located below the lower structure layer or above the upper structure layer, and the stress layer drives the four-layer structure to curl to form a three-dimensional structure; The flexible substrate, the temperature sensing layer and the insulating layer are in a planar structure and are located directly below the three-dimensional structure; the packaging layer wraps the planar structure and the three-dimensional structure and is connected to the flexible substrate.

2. A flexible tactile sensor, characterized in that, it includes a flexible substrate, a stress layer, a lower structure layer, a row selection wire layer, an insulating layer, a strain gauge layer, a column selection wire layer, an upper structure layer and a packaging layer; wherein the lower structure layer, the row selection wire layer, the insulating layer, the strain gauge layer, the column selection wire layer, and the upper structure layer are arranged in sequence from bottom to top, and the upper structure layer and the lower structure layer wrap the row selection wire layer, the insulating layer, the strain gauge layer, and the column selection wire layer to form a six-layer structure; the stress layer is located below the lower structure layer or above the upper structure layer, and the stress layer drives the six-layer structure to curl to form a three-dimensional structure; through holes are left on the insulating layer for the connection of the row selection wire layer and the column selection wire layer at specific positions; the packaging layer wraps the three-dimensional structure and is connected to the flexible substrate.

3. The flexible tactile sensor according to claim 1 or 2, characterized in that, the materials of the flexible substrate, the insulating layer, the upper structure layer and the lower structure layer are flexible and biocompatible insulating materials.

4. The flexible tactile sensor according to claim 3, characterized in that, the materials of the flexible substrate, the insulating layer, the upper structure layer and the lower structure layer are one of the following: polyimide, polyethylene terephthalate, polyethylene naphthalate, polydimethylsiloxane, polyurethane, parylene, epoxy resin, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid.

5. The flexible tactile sensor according to claim 1 or 2, characterized in that, The material of the stress layer is SiO 2 , or Si 3 N 4 , or polycrystalline / amorphous silicon, or other materials that generate intrinsic stress during thin film preparation.

6. The flexible tactile sensor according to claim 1 or 2, characterized in that, the materials of the temperature sensing layer, the strain gauge layer and the wire layer are metal materials or alloy materials.

7. The flexible tactile sensor according to claim 1 or 2, characterized in that, the material of the packaging layer is a silicone material and is prepared by casting encapsulation; the mold used in the process of the casting encapsulation is prepared by 3D printing or CNC machining, and the shape of the casting encapsulation is hemispherical, or conical, or pyramid-shaped, or cuboid-shaped, respectively forming a hemispherical packaging layer, or a conical packaging layer, or a pyramid-shaped packaging layer, or a cuboid-shaped packaging layer.

8. The flexible tactile sensor according to claim 1 or 2, characterized in that, The temperature sensing layer and the wire layer are provided with electrodes connected to an external circuit, and the functions of the external circuit include one of crosstalk suppression, channel selection, signal processing, analog-to-digital conversion, wireless data transmission, and energy supply.

9. A method for manufacturing the flexible tactile sensor according to claim 1, characterized in that it comprises the following steps: Preparing a flexible substrate on a substrate; Sequentially preparing a temperature sensing layer, an insulating layer, a sacrificial layer, a stress layer, a lower structure layer, a strain gauge layer, a wire layer, and an upper structure layer on the flexible substrate; Removing the sacrificial layer by wet etching, so that the stress layer drives the lower structure layer, the strain gauge layer, the wire layer, and the upper structure layer supported by it to curl, forming a three-dimensional structure; Preparing a packaging layer on the three-dimensional structure; Detaching the flexible substrate from the substrate to obtain the flexible tactile sensor.

10. A method for manufacturing the flexible tactile sensor according to claim 2, characterized in that it comprises the following steps: Preparing a flexible substrate on a substrate; Sequentially preparing a sacrificial layer, a stress layer, a lower structure layer, a row selection wire layer, an insulating layer, a strain gauge layer, a column selection wire layer, and an upper structure layer on the flexible substrate; Removing the sacrificial layer by wet etching, so that the stress layer drives the lower structure layer, the row selection wire layer, the insulating layer, the strain gauge layer, the column selection wire layer, and the upper structure layer supported by it to curl, forming a three-dimensional structure; Preparing a packaging layer on the three-dimensional structure; Detaching the flexible substrate from the substrate to obtain the flexible tactile sensor.

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