Flexible capacitive tactile sensor, method of making the same, and tactile sensing system

Abstract

A flexible capacitive tactile sensor, a preparation method of the flexible capacitive tactile sensor and a tactile sensing system. The flexible capacitive tactile sensor comprises: a first flexible electrode layer, on which a first electrode array is arranged; a second flexible electrode layer, on which a second electrode array is arranged; and an ionic gel film dielectric layer, which is arranged between the first flexible electrode layer and the second flexible electrode layer. The flexible capacitive tactile sensor disclosed in the present application can have high flexibility, high sensing density and high sensing sensitivity.

Description

Technical Field

[0001] Embodiments of this disclosure relate to a flexible capacitive tactile sensor and its fabrication method, a tactile sensing system, and an electronic device. Background Technology

[0002] With the development of intelligent robot technology and the deepening of robot application scenarios, people hope that robots can not only complete pre-set mechanical movements, but also perceive the external environment and provide feedback. The integration of tactile sensors with robots has become an important direction for development.

[0003] However, existing tactile sensors are typically thin-film capacitive pressure gauges or strain gauges. These sensors are mostly placed in specific locations for sensing. Because a single tactile sensor independently detects the touch signal (e.g., pressure signal) at a specific location, it can only detect information at that specific location and cannot form an omnidirectional sensing system, thus failing to provide tactile information capable of handling complex situations. Currently, the materials used in tactile sensors are mostly rigid, resulting in poor conformal adhesion when placed on uneven surfaces (e.g., on a robot arm). Furthermore, current tactile sensors have low sensitivity and poor resolution for tactile sensation. Summary of the Invention

[0004] At least one embodiment of this disclosure provides a flexible capacitive tactile sensor, comprising: a first flexible electrode layer having a first electrode array disposed thereon; a second flexible electrode layer having a second electrode array disposed thereon; and an ion gel thin film dielectric layer disposed between the first flexible electrode layer and the second flexible electrode layer.

[0005] At least one embodiment of this disclosure also provides a method for fabricating a flexible capacitive tactile sensor, comprising: fabricating a first flexible electrode layer having a first electrode array disposed thereon; fabricating an ion gel film dielectric layer and placing the ion gel film dielectric layer on top of the first flexible electrode layer; fabricating a second flexible electrode layer; placing the second flexible electrode layer on top of the ion gel film dielectric layer; and encapsulating the first flexible electrode layer, the ion gel film dielectric layer, and the second flexible electrode layer into the flexible capacitive tactile sensor.

[0006] At least one embodiment of this disclosure also provides a tactile sensing system, comprising: an excitation circuit configured to output a sensing excitation signal to the first flexible electrode layer and the second flexible electrode layer; the aforementioned flexible capacitive tactile sensor configured to determine a touch sensing signal based on the sensing excitation signal according to a change in the contact area between at least one of the first flexible electrode layer and the second flexible electrode layer and the dielectric layer of the ionogel film; a signal detection circuit configured to receive the touch sensing signal from the flexible capacitive tactile sensor; and a signal processor configured to process the touch sensing signal and determine a touch position or touch pressure.

[0007] At least one embodiment of this disclosure also provides an electronic device, including: a tactile sensing detection surface, on which the above-described flexible capacitive tactile sensor is attached. Attached Figure Description

[0008] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this disclosure, and are not intended to limit this disclosure.

[0009] Figure 1A A schematic diagram of a flexible capacitive tactile sensor provided in some embodiments of the present disclosure is shown.

[0010] Figure 1B A schematic diagram illustrating the principle of a flexible capacitive tactile sensor provided in some embodiments of this disclosure is shown.

[0011] Figure 2A A schematic diagram of a portion of a first electrode array in a flexible capacitive tactile sensor provided in some embodiments of the present disclosure is shown.

[0012] Figure 2B A schematic diagram of a portion of a second electrode array in a flexible capacitive tactile sensor provided in some embodiments of the present disclosure is shown.

[0013] Figure 2C A schematic diagram of the electrode array arrangement of a flexible capacitive tactile sensor provided in some embodiments of this disclosure is shown.

[0014] Figure 3A A schematic diagram of a portion of a first electrode array in a flexible capacitive tactile sensor provided in some embodiments of the present disclosure is shown.

[0015] Figure 3B A schematic diagram of a portion of a second electrode array in a flexible capacitive tactile sensor provided in some embodiments of the present disclosure is shown.

[0016] Figure 3CA schematic diagram showing the overlapping of a first electrode array and a second electrode array of a flexible capacitive tactile sensor provided in some embodiments of the present disclosure is shown.

[0017] Figure 4 A flowchart illustrating a method for fabricating a flexible capacitive tactile sensor according to some embodiments of the present disclosure is shown.

[0018] Figure 5 The sensitivity comparison between the flexible capacitive tactile sensor provided in some embodiments of this disclosure and a conventional electrostatic capacitive sensor is shown.

[0019] Figure 6 An equivalent circuit diagram of a tactile sensing system provided in some embodiments of this disclosure is shown.

[0020] Figure 7 A schematic diagram of an electronic device provided in some embodiments of the present disclosure is shown. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0022] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “including,” “comprising,” or “containing,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0023] Typically, intelligent robots can react to their external environment. This requires them to be able to perceive information about their surroundings. Specifically, intelligent robots can use non-contact sensors that can sense vision, proximity, and distance, as well as contact sensors that can sense pressure, tactile sensation, and pressure sensitivity. Tactile sensors, as a typical type of contact sensor, enable intelligent robots to perceive the pressure they come into contact with.

[0024] One or more embodiments of this disclosure provide a large-area, high-density flexible ionic capacitive tactile sensor as the electronic skin of an intelligent robot, making the tactile sensor flexible overall and significantly improving the sensitivity of the tactile sensing system. Specifically, one or more embodiments of this disclosure achieve flexibility, high sensing density, and high sensing sensitivity of the tactile sensing system by directly fabricating a flexible tactile sensing array on a flexible thin-film substrate and using a flexible ionic sensing active material as the dielectric layer. The flexible electrode array is combined with data readout circuitry and data processing software to form a large-area electronic skin.

[0025] The embodiments and examples of this disclosure will now be described in detail with reference to the accompanying drawings.

[0026] Figure 1A This is a schematic diagram of a flexible capacitive tactile sensor 10 provided in some embodiments of this disclosure. Figure 1B A schematic diagram illustrating the principle of a flexible capacitive tactile sensor 10 provided for some embodiments of this disclosure.

[0027] like Figure 1A As shown, the flexible capacitive tactile sensor 10 includes a first flexible electrode layer 101, a second flexible electrode layer 102, and an ion gel film dielectric layer 103. A first electrode array 1012 is disposed on the first flexible electrode layer 101. A second electrode array 1022 is disposed on the second flexible electrode layer 102. The ion gel film dielectric layer 103 is disposed between the first flexible electrode layer 101 and the second flexible electrode layer 102.

[0028] Furthermore, the flexible capacitive tactile sensor 10 may also include other structural or functional layers as needed. For example, in some embodiments, the flexible capacitive tactile sensor 10 may include a lead layer for transmitting touch sensing signals. As another example, the flexible capacitive tactile sensor 10 may also include a protective layer, such as a flexible thin film protective layer. For example, in some embodiments, the flexible capacitive tactile sensor 10 may also include other functional layers, which can be bonded to the first flexible electrode layer 101 or the second flexible electrode layer 102 using optically transparent adhesive (OCA adhesive). The embodiments disclosed herein do not specifically limit other structures of the flexible capacitive tactile sensor 10.

[0029] The first flexible electrode layer 101 includes a first flexible thin film layer 1011, and a first electrode array 1012 is fabricated on the first flexible thin film layer 1011. The second flexible electrode layer 102 includes a second flexible thin film layer 1021, and a second electrode array 1022 is fabricated on the second flexible thin film layer 1021. The flexible capacitive tactile sensor 10 is encapsulated with a flexible thin film material. Because all components of the flexible capacitive tactile sensor 10 are made of flexible materials, the whole can undergo a certain degree of bending and stretching deformation, ensuring stable tactile sensing performance under certain deformation. When the flexible capacitive tactile sensor 10 is applied to a robot, it can be perfectly attached to the robot's outer arm, and the sensing signal is more stable and accurate. The first electrode array 1012 and the second flexible electrode layer 102 are large-area flexible electrode layers. Therefore, the flexible capacitive tactile sensor 10 can be attached to the robot's outer arm in a conformal manner, realizing omnidirectional tactile sensing of the robot.

[0030] Specifically, to form a large-area flexible electrode layer, the first electrode array 1012 can be fabricated on the first flexible thin film layer 1011 by silver nanoparticle spraying or physical vapor deposition. Similarly, the second electrode array 1022 can also be fabricated on the second flexible thin film layer 1021 by silver nanoparticle spraying or physical vapor deposition. Specifically, physical vapor deposition methods include evaporation (e.g., electron beam evaporation) or sputtering. The first flexible thin film layer 1011 and the second flexible thin film layer 1021 can be composed of at least one of the following materials: thermoplastic polyurethane elastomer rubber (TPU), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), nylon 6 (PA6), polylactic acid (PLA), polyacrylonitrile (PAN), and polyethersulfone (PES).

[0031] For example, a mask with a pre-defined electrode pattern can be prepared first, and then a patterned array of electrodes can be sprayed onto a flexible polyethylene terephthalate (PET) film using silver nanowire spraying. Silver nanowires are nanoscale silver wires. In addition to the excellent conductivity of silver, silver nanowires also possess light transmittance and flexibility due to their nanoscale size effect, thus achieving high flexibility and conductivity. Alternatively, an Au film can be deposited onto a flexible film (e.g., polyethylene terephthalate (PET)) using electron beam evaporation to create a patterned electrode array. Electron beam evaporation is a physical vapor deposition process. Under the coordination of an electromagnetic field, high-energy electrons are precisely used to bombard a target material (e.g., aluminum (Au)) within a crucible, causing it to melt and deposit onto a substrate (e.g., a flexible film), thereby depositing a high-purity, high-precision electrode array. Of course, other methods can also be used to fabricate the first electrode array 1012 and the second electrode array 1022 on the flexible film, and this disclosure does not limit this.

[0032] Thus, flexible electrode layers are formed in the first flexible electrode layer 101 and the second flexible electrode layer 102.

[0033] like Figure 1B As shown, two electrode-electrolyte interfaces are formed between the conductive electrodes of the first electrode array 1012 and the second electrode array 1022 and the dielectric layer 103 of the ion gel film, respectively. For example, Figure 1B An electrode-electrolyte interface 1041 is formed between the first electrode array 1012 and the ion gel film dielectric layer 103, and another electrode-electrolyte interface is formed between the second electrode array 1022 and the ion gel film dielectric layer 103. At the electrode-electrolyte interface 1041, surface charges within the first electrode array 1012 adsorb ions from the electrolyte in the ion gel film dielectric layer 103 (e.g., ...). Figure 1B(As shown by the white circle in the diagram). Thus, at the electrode-electrolyte interface 1041, an ion interface layer is formed on the side of the ion gel film dielectric layer with a charge quantity equal to but opposite in sign to the surface charge quantity inside the first electrode array 1021. For example, when a positive voltage is applied to the first electrode array 1012, a positively charged electron layer is formed on the side of the electrode-electrolyte interface 1041 near the first electrode array 1012, while a negatively charged electron layer is formed on the side of the electrode-electrolyte interface 1041 near the ion dielectric array 103. Due to the presence of the electrode-electrolyte interface 1041, the positrons in the positively charged electron layer and the negatively charged ions in the negatively charged electron layer cannot cross the boundary and neutralize each other, thus forming a stable capacitor structure at the electrode-electrolyte interface 1041. Similarly, a stable capacitor structure is also formed at the electrode-electrolyte interface between the second electrode array 1022 and the ion gel film dielectric layer 103. Therefore, the first electrode array 1012, the second electrode array 1022, and the ion gel film dielectric layer 103 constitute an ionic double-layer capacitor.

[0034] Preferably, the surface of the ion gel film dielectric layer 103 may have a microstructure. Before the application of touch pressure, the area of ​​the electrode-electrolyte interface 1041 formed between the first electrode array 1012 and the ion gel film dielectric layer 103 is small. However, after the application of touch pressure, due to the deformation of the microstructure, the area of ​​the electrode-electrolyte interface 1041 formed between the first electrode array 1012 and the ion array layer 103 increases. According to the capacitance calculation formula...

[0035]

[0036] Where C is the capacitance of the capacitor, ε is the dielectric constant of the material, S is the contact area between the first electrode array 1012 / second electrode array 1013 and the ion gel film dielectric layer 103, k is the electrostatic constant, and d is the distance between the first electrode array 1012 / second electrode array 1013 and the ion gel film dielectric layer 103. The dielectric constant ε of the material usually does not change. In the flexible capacitive tactile sensor 10, the first electrode array 1012 and the second electrode array 1022 are placed facing each other, so the electric field of the flexible capacitive tactile sensor 10 can be approximated as a parallel electric field. As... Figure 1B As shown, under pressure, the contact area of ​​the electrode-electrolyte interface 1041 increases due to the deformation of the microstructure. Furthermore, since the distance d between the contact areas of the first electrode array 1012 / second electrode array 1013 and the ion gel film dielectric layer 103 is at the nanometer level, the capacitance of the flexible capacitive tactile sensor 10 increases rapidly with the increase of the contact area S, thus exhibiting high sensitivity.

[0037] Therefore, the above embodiments of this disclosure achieve flexibility, high sensing density, and high sensing sensitivity in the tactile sensing system by directly fabricating the flexible tactile electrode array on the substrate of the flexible thin film material and using a flexible ionic sensing active material as the dielectric layer.

[0038] Figure 2A This is a schematic diagram of a portion of a first electrode array 1012 in a flexible capacitive tactile sensor 10 provided in some embodiments of the present disclosure. Figure 2B This is a schematic diagram of a portion of a second electrode array 1022 in a flexible capacitive tactile sensor 10 provided in some embodiments of this disclosure. Figure 2C This is a schematic diagram of the electrode array arrangement of a flexible capacitive tactile sensor 10 provided in some embodiments of this disclosure.

[0039] exist Figure 2A and Figure 2B In the embodiment shown, the electrodes in the first electrode array 1012 are connected in series in a first direction, while the electrodes in the second electrode array 1022 are connected in series in a second direction.

[0040] The first electrode array 1012 and the second electrode array 1022 are arranged opposite to each other, and the first direction and the second direction are different. Optionally, the first direction and the second direction are perpendicular.

[0041] The electrode pattern of at least one of the electrodes in the first electrode array 1012 or the second electrode array 1022 is circular, rectangular, or square. For example, the electrode pattern can be... Figure 2A The size shown is 3x3mm. 2 The electrode pattern is a square. Of course, the electrode pattern can also be other sizes, such as a circle with a diameter of 3mm.

[0042] The electrodes have a first length in a first direction and a second length in a second direction. The width of the connecting line between the electrodes on the first electrode array 1012 along the first direction is less than the second length, and the width of the connecting line between the electrodes on the second electrode array 1022 along the second direction is less than the first length. For example, as... Figure 2A As shown, the first length of the electrode is 3 mm, and the second length is also 3 mm. The width of the connecting line between the electrodes on the first electrode array 1012 along the first direction is 0.8 mm, which is smaller than the second length of 3 mm. Figure 2B As shown, the width of the connecting line of the electrodes on the second electrode array 1022 along the second direction is also 0.8 mm, which is less than the first length of 3 mm.

[0043] The electrodes on the first electrode array 1012 are spaced apart in the first direction by a third length (e.g., Figure 2AThe second electrode array 1022 has a spacing of 3 mm in the second direction, which is a fourth length (e.g., 3 mm). Figure 2B (The first to fourth lengths can be the same or different. The first, second, third, and fourth lengths are all less than 5 mm.)

[0044] See Figure 2C The first electrode array 1012, the second electrode array 1022, and the ion gel thin film dielectric layer 103 are formed. Figure 2C The diagram shows a "sandwich" structure, with the ion gel film dielectric layer 103 located between the first electrode array 1012 and the second electrode array 1022. The first electrode array 1012 consists of m series electrodes parallel to a first direction, and the second electrode array 1022 consists of n series electrodes parallel to a second direction. The first direction and the second direction are different. Optionally, the first direction is perpendicular to the second direction, so that the region where the first electrode array 1012 and the second electrode array 1022 intersect forms an m*n electrode array.

[0045] The ion-gel thin film dielectric layer 103 can be composed of a polymer and an ionic liquid. Optionally, the polymer may include poly(vinylidene fluoride-hexafluoropropylene). The ionic liquid may include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. The poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) can form a polymer mesh, which can constitute a stable network structure. The 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]) can be attached to the polymer mesh; it is ion-rich and can serve as an active material for capacitive sensing. After the polymer carrying the ionic liquid is cured into a film, the ion-gel thin film dielectric layer 103 can be placed as a solid ion-gel dielectric layer between the first electrode array 1012 and the second electrode array 1022. Specifically, the ion-gel thin film dielectric layer 103 can be cut into cubes of the same size as the electrodes, for example, 3*3mm. 2 A square of multiple cut ionogel thin film dielectric layers 103 is placed above each electrode in the first electrode array 1012. Empty spaces (e.g., gaps between multiple series electrodes) can be filled with various fillers, such as transparent adhesive or double-sided tape. Next, a second electrode array 1022 is stacked on top of the ionogel thin film dielectric layer 103. In one embodiment, the first electrode array 1012 and the second electrode array 1022 are bonded together using fillers in the empty spaces, thereby encapsulating a flexible capacitive tactile sensor 10 with an m*n electrode array.

[0046] Therefore, when the flexible capacitive tactile sensor 10 receives touch pressure, it can locate the change in capacitance of one or more electrodes in the m*n electrode array, thereby determining the position and pressure of the touch point. The above embodiments of this disclosure achieve flexibility, high sensing density, and high sensing sensitivity in the tactile sensing system by directly fabricating (e.g., printing) the flexible tactile electrode array on a substrate of flexible thin film material and using a flexible ion-sensitive active material as the dielectric layer. Compared to existing rigid thin-film capacitive pressure gauges or strain gauges, since the flexible capacitive tactile sensor 10 is composed entirely of flexible materials, it can better adhere to curved or uneven robot surfaces and is less prone to falling off, thus achieving better conformal adhesion.

[0047] like Figures 2A to 2C The electrode arrangement shown is clear and can simplify the testing workload (a whole series of electrodes can be tested at once), reduce the wiring space of the leads and reduce crosstalk between electrodes, thereby achieving a high-density electrode arrangement.

[0048] It is worth noting that, Figures 2A to 2C The example shown is only schematically an example of the electrode distribution of a portion of the first electrode array 1012 and the second electrode array 1022. However, the embodiments of this disclosure do not limit the number, arrangement and specific position of the electrodes included in the first electrode array 1012 and the second electrode array 1022, as long as the flexible capacitive tactile sensor 10 can realize the detection of touch position and touch pressure.

[0049] Figure 3A This is a schematic diagram of a portion of a first electrode array 1012 in a flexible capacitive tactile sensor 10 provided in some embodiments of the present disclosure. Figure 3B This is a schematic diagram of a portion of a second electrode array 1022 in a flexible capacitive tactile sensor 10 provided in some embodiments of this disclosure. Figure 3C This is a schematic diagram showing the overlap of the first electrode array 1012 and the second electrode array 1022 of the flexible capacitive tactile sensor 10 provided in some embodiments of this disclosure.

[0050] Similar to the embodiments described above, at least one electrode in the plurality of electrodes of the first electrode array 1012 or the second electrode array 1022 has an electrode pattern that is circular, rectangular, or square. For example, the electrode pattern may be... Figure 3A and Figure 3B The size shown is 3x3mm. 2 The electrode pattern is a square. Of course, the electrode pattern can also be other sizes, such as a circle with a diameter of 3mm.

[0051] The first electrode array 1012 and the second electrode array 1022 are arranged opposite to each other, and each electrode in the first electrode array 1012 and the second electrode array 1022 has a separate lead. Figure 3A As shown, the first electrode array 1012 has leads as shown by solid lines, such as Figure 3B As shown, the second electrode array 1022 has leads as indicated by dashed lines.

[0052] like Figure 3C As shown, the leads of two electrodes disposed opposite each other in the first electrode array 1012 and the second electrode array 1022 do not intersect in the direction of overlap of the two electrodes (solid and dashed lines do not intersect), thus there is no overlapping area after the leads of the first electrode array 1012 and the second electrode array 1022 are stacked opposite each other. Similarly, the spacing between each electrode can be less than 5 mm. Due to the small width of the leads, they can be arranged in the spacing between the electrodes. Since each electrode has a separate lead, crosstalk between electrodes can be reduced.

[0053] like Figures 3A to 3C The electrode arrangement shown in the diagram, in which two electrodes arranged opposite each other in the first electrode array 1012 and the second electrode array 1022 and the ion gel film dielectric layer between them constitute a double-layer capacitor, each of which can work independently as a tactile sensor, thus facilitating tactile detection in complex spaces.

[0054] It is worth noting that, Figures 3A to 3C The illustration only shows an example of the electrode and lead distribution of a portion of the first electrode array 1012 and the second electrode array 1022. However, the embodiments of this disclosure do not limit the number, arrangement, lead arrangement and specific position of the electrodes included in the first electrode array 1012 and the second electrode array 1022, as long as the flexible capacitive tactile sensor 10 can realize the detection of touch position and touch pressure.

[0055] Figure 4 A flowchart of a method 400 for fabricating a flexible capacitive tactile sensor 10 according to some embodiments of the present disclosure is shown. The fabrication method 400 according to some embodiments of the present disclosure includes the following steps. Although each step 401-403 of the fabrication method 400 is shown in sequence, those skilled in the art will understand that the steps can be varied. Figure 4 The sequences shown may differ, or these steps may be performed simultaneously. Examples of such alternative sequences may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplementary, simultaneous, reverse, or other variant sequences.

[0056] In step 401, a first flexible electrode layer 101 can be prepared. A first electrode array 1012 is disposed on the first flexible electrode layer 101. The electrodes in the first electrode array 1012 are connected in series in a first direction. Specifically, a patterned first electrode array 1012 can be sprayed onto the first flexible thin film layer 1011 of the first flexible electrode layer 101 using a silver nanowire spraying method. Alternatively, a patterned first electrode array 1012 can be deposited onto the first flexible thin film layer 1011 of the first flexible electrode layer 101 using an electron beam evaporation method. As described above, the first flexible thin film layer 1011 can be composed of at least one of the following materials: thermoplastic polyurethane elastomer rubber (TPU), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), nylon 6 (PA6), polylactic acid (PLA), polyacrylonitrile (PAN), and polyethersulfone (PES), etc.

[0057] For example, a fabricated photomask can be used to assist in the aforementioned silver nanowire spraying and electron beam evaporation processes. Specifically, each electrode in the electrode pattern of the photomask can be circular, rectangular, or square. The length of the electrode in a first direction is a first length, and the length in a second direction is a second length. The width of the connecting line between the electrodes on the first electrode array along the first direction is less than the second length, and the width of the connecting line between the electrodes on the second electrode array along the second direction is less than the first length. The spacing between the electrodes on the first electrode array in the first direction is a third length, and the spacing between the electrodes on the second electrode array in the second direction is a fourth length. For example, each electrode is 3x3mm. 2 The electrodes are square; each electrode is connected in series by a 0.8mm connecting wire; the spacing between each series of electrodes is 3mm.

[0058] In step 402, an ion gel film dielectric layer 103 can be prepared and placed on the first flexible electrode layer 101. Specifically, the sensitivity of the flexible capacitive tactile sensor 10 can be improved by fabricating the ion gel film dielectric layer 103 with a microstructured surface using a casting method. The process of preparing the ion gel film dielectric layer 103 by casting may include preparing a mixed solution of a polymer and an ionic liquid. For example, the polymer may include poly(vinylidene fluoride-hexafluoropropylene), and the ionic liquid may include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. Optionally, the mass ratio of the ionic liquid to the polymer is from 1:2 to 6:1. An exemplary ratio is 3:1. Such a ratio can improve the sensitivity of the flexible capacitive tactile sensor 10. Then, the mixed solution is poured onto a microstructure template. The specific shape of the microstructure on the microstructure template is not limited, and its size can be at the sub-millimeter level. Finally, after the mixed solution has solidified, the dielectric layer 103 of the ion gel film is obtained.

[0059] For example, the preparation method of the above-mentioned mixed solution may further include the following steps: for example, firstly, a polymer (e.g., poly(vinylidene fluoride-hexafluoropropylene)) is dissolved in a solvent (acetone) to form a first mixed solution. Optionally, the mass ratio of polymer to solvent can be 1:1 to 1:20. An exemplary ratio is a polymer to solvent mass ratio of 1:10. Such a ratio can improve the sensitivity of the flexible capacitive tactile sensor 10. The first mixed solution is then stirred until clear using a magnetic stirrer. An ionic liquid (e.g., 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide) is added to the clear first mixed solution to form a second mixed solution, and the second mixed solution is stirred until clear using a magnetic stirrer to form a mixed solution. The mixed solution is poured onto a microstructure template, and the template is placed in a fume hood to allow the acetone to evaporate naturally, thereby obtaining a solidified ion gel. The ion gel is peeled off from the template to obtain an ion gel film with a surface microstructure. The ion gel microstructure film is cut into a shape the same as the electrode size, for example, 3*3 mm. 2 The square blocks. This preparation method allows for the simple and convenient fabrication of highly sensitive ion-gel thin film dielectric layers 103.

[0060] In step 403, a second flexible electrode layer 102 is prepared, on which a second electrode array 1022 is disposed, and the electrodes on the second electrode array 1022 are connected in series in a second direction. Similarly, a patterned second electrode array 1022 can be patterned by spraying silver nanowires onto the second flexible thin film layer 1021 of the second flexible electrode layer 102. Alternatively, a patterned second electrode array 1022 can be deposited onto the second flexible thin film layer 1021 of the second flexible electrode layer 102 by electron beam evaporation. As described above, the second flexible thin film layer 1021 can be composed of at least one of the following materials: thermoplastic polyurethane elastomer rubber (TPU), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), nylon 6 (PA6), polylactic acid (PLA), polyacrylonitrile (PAN), and polyethersulfone (PES), etc. The electrode pattern of the second electrode array 1022 can be similar to the electrode pattern of the first electrode array 1012, but must be different in the series direction.

[0061] In step 404, the second flexible electrode layer 102 is placed on top of the ion gel film dielectric layer 103, such that the first electrode array 1012 and the second electrode array 1022 are arranged opposite each other, and the first direction and the second direction are different. Optionally, the first direction and the second direction are perpendicular. In step 405, the first flexible electrode layer 101, the ion gel film dielectric layer 103, and the second flexible electrode layer 102 are encapsulated into a flexible capacitive tactile sensor 10.

[0062] For example, any unused spaces in the first flexible electrode layer 101 that do not contact the ionogel film dielectric layer (e.g., the gaps between multiple series electrodes) can be filled using various fillers, such as double-sided tape. Next, the second flexible electrode layer 102 is placed on top of the ionogel film dielectric layer 103. In one embodiment, the first flexible electrode layer 101 and the second flexible electrode layer 102 are bonded together using fillers in the unused spaces, thus completing the encapsulation of the flexible capacitive tactile sensor 10.

[0063] Figure 5 A sensitivity comparison of the flexible capacitive tactile sensor 10 provided in some embodiments of this disclosure with that of a conventional electrostatic capacitive sensor.

[0064] like Figure 5 As shown, a traditional electrostatic capacitive sensor exhibits a capacitance change of approximately 10 kPa * 0.003 kPa when subjected to a pressure of 10 kPa. -1 =0.03. Under the same pressure of 10 kPa, the change in capacitance is approximately 10 kPa * 0.28 kPa. -1=2.8. Therefore, it can be seen that the flexible capacitive tactile sensor 10, which uses ionogel as the dielectric layer, improves sensitivity by more than 10 times compared to traditional electrostatic capacitive sensors.

[0065] Figure 6 Equivalent circuit diagram of a tactile sensing system 60 provided for some embodiments of this disclosure.

[0066] The tactile sensing system 60 includes an excitation circuit 61, a flexible capacitive tactile sensor 10, a signal detection circuit 62, and a signal processor 63.

[0067] The excitation circuit 61 is configured to output a sensing excitation signal to the first flexible electrode layer 1012 and the second flexible electrode layer 1022. Figure 6 In this circuit, the excitation circuit 61 can be an AC power supply or a pulse signal source. For example, for... Figures 3A to 3B In the embodiment shown with individual leads for each electrode, electrode A in the first flexible electrode layer 1012 can be connected to one end of the excitation circuit 61, and electrode B in the second flexible electrode layer 1022, which is opposite to electrode A, can be connected to the other end of the excitation circuit 61.

[0068] The flexible capacitive tactile sensor 10 is configured to determine a touch sensing signal based on a sensing excitation signal, according to a change in the contact area between at least one of the first flexible electrode layer 101 and the second flexible electrode layer 102 and the ion-gel thin film dielectric layer 103. For example, the overlapping area of ​​electrode A and electrode B can be equivalent to... Figure 6 The capacitor C is located in the circuit. The remaining wires can be considered as a resistor R. c .

[0069] The signal detection circuit 62 is configured to receive touch sensing signals from the flexible capacitive tactile sensor 10. Optionally, the signal detection circuit 62 may be... Figure 6 The sampling resistor R in sample .like Figure 6 As shown, the excitation circuit 61, the flexible capacitive tactile sensor 10, and the signal detection circuit 62 form a loop. When an external force is applied, the contact area between at least one of electrodes A and B and the dielectric layer of the ion-gel film changes, thereby changing the capacitance value of capacitor C. Furthermore, the sampling resistor R... sample The voltage change across the two ends. Sampling resistor R sample The voltage at both ends can be used as the touch sensing signal received by the signal detection circuit 62.

[0070] The signal detection circuit 62 then outputs the touch sensing signal to the signal processor 63. The signal processor 63 is configured to process the touch sensing signal and determine the touch position or touch force. The signal detection circuit 62 can be implemented as an analog signal processor that can convert the touch sensing signal into an analog signal, or it can be implemented as a data signal processor (DSP), field-programmable gate array (FPGA), etc., that can convert the touch sensing signal into a digital signal. The embodiments of this disclosure do not limit the implementation of the signal detection circuit 62.

[0071] In addition, for Figures 2A to 2C The electrode arrays described herein, since the first electrode array 1012 and the second electrode array 1022 of the flexible capacitive tactile sensor 10 are large-area, high-density electrode arrays, and the electrodes in the first electrode array are connected in series in a first direction while the electrodes in the second electrode array are connected in series in a second direction, the excitation circuit 61 may include a multiplexer for scanning the electrode arrays by rows and columns, one end of which is connected to one end of an AC power supply. For example, one end of each series electrode in the first electrode array 1012 may be connected to one end of the multiplexer, with the other end left floating. One end of each series electrode in the second electrode array 1022 may be connected to the other end of the excitation circuit 61, with the other end left floating. Alternatively, both ends of each series electrode in the first electrode array 1012 may be connected to the multiplexer. Both ends of each series electrode in the second electrode array 1022 may be connected to the signal detection circuit 62. For example, in the first electrode array 1012, the two ends of each series electrode are connected to the two ends of the excitation circuit 61, and in the second electrode array 1022, the two ends of each series electrode are connected to the signal detection circuit 62. This disclosure does not apply to 2A to... Figure 2C The method of row and column scanning of the electrode array described in the text is limited.

[0072] Optionally, the multiplexer periodically selects one series electrode in the first electrode array 1012. Assume that the series electrodes A1', A2'…A… in the first electrode array 1012 are… k The formed series electrodes are selected at a certain moment. At that moment, electrodes B1', B2'...B1' in the region where the second electrode array 1022 overlaps with the series electrodes are selected. k 'With electrodes A1', A2'...A k The resulting capacitor is conducting. The overlapping area of ​​electrodes A1' and B1' can be equivalent to... Figure 6 The capacitance C in the circuit. The wires connecting electrodes A1' and B1' can be considered equivalent to a resistor R. c At this point, a total of k capacitors C are conducting. For example... Figure 6As shown, the excitation circuit 61, any one of the k capacitors C, and the signal detection circuit 62 can form a loop, resulting in a total of k conducting loops. If the overlapping area of ​​electrodes A1' and B1' is touched at this time, the capacitance formed by electrodes A1' and B1' will change drastically. Consequently, the sampling resistor R... sample The voltage change across the two ends. Sampling resistor R sample The voltage across the terminals can serve as the touch sensing signal received by the signal detection circuit 62. The signal detection circuit 62 then outputs this touch sensing signal to the signal processor 63. The signal processor 63 processes the touch sensing signal and determines the touch position or touch force.

[0073] Therefore, during the movement of the intelligent robot, when the robot comes into contact with an object or person, tactile pressure is generated. The flexible capacitive tactile sensor 10 can detect this tactile pressure by detecting changes in its capacitance. The location of the object the robot is touching can be determined based on the position of the response in the electrode array, and the magnitude of the contact force can be roughly determined based on the change in capacitance. By analyzing the touch sensing signal, the contact status between the robot and external objects can be obtained, providing information for the robot's next action. The flexible capacitive tactile sensor 10 according to the embodiments of this disclosure has significant application value in robot safety and human-computer interaction.

[0074] It is worth noting that, Figure 6 Only one example of the tactile sensing system 60 is shown schematically, but the circuit connection of the tactile sensing system 60 in the embodiments of this disclosure is not limited, as long as the flexible capacitive tactile sensor 10 can detect the touch position and touch pressure.

[0075] Figure 7 This is a schematic diagram of an electronic device 70 provided in some embodiments of this disclosure.

[0076] For example, in some embodiments, the electronic device 70 includes a flexible capacitive tactile sensor 10 and a mechanical tactile sensing detection surface 71.

[0077] For example, if the electronic device 70 is an intelligent robot, the tactile sensing detection surface 71 can be at least a part of the robot arm. The aforementioned flexible capacitive tactile sensor 10 can be attached to the tactile sensing detection surface 71. This flexible capacitive tactile sensor 10 can be connected to other components in the aforementioned tactile sensing system 60 to detect the tactile pressure generated when the robot touches an object or person during robot movement. The electronic device 70 can also be a wearable device; when worn, it can collect and analyze touch data through the flexible capacitive tactile sensor 10.

[0078] One or more embodiments of this disclosure disclose a large-area, high-density flexible capacitive sensor 10 as the electronic skin of a smart robot / wearable device, making the flexible capacitive sensor 10 flexible overall and significantly improving the sensitivity of the tactile sensing system 60. Furthermore, the flexible capacitive sensor 10 can be easily attached to the tactile sensing detection surface 71 of the electronic device 70, achieving omnidirectional tactile sensing of surrounding objects.

[0079] Specifically, one or more embodiments of this disclosure achieve flexibility, high sensing density, and high sensing sensitivity in the tactile sensing system by directly fabricating a flexible tactile sensing array on a substrate of a flexible thin film material and using a flexible ionic sensing active material as the dielectric layer. The flexible electrode array, combined with data readout circuitry and data processing software, forms a large-area electronic skin that is easy to attach.

[0080] The following points need to be explained:

[0081] (1) The accompanying drawings of the embodiments of this disclosure only involve the structures involved in the embodiments of this disclosure. Other structures can be referred to the general design.

[0082] (2) For clarity, the thickness of layers or regions is enlarged or reduced in the drawings used to describe embodiments of the present disclosure, i.e., these drawings are not drawn to actual scale. It will be understood that when an element such as a layer, film, region or substrate is referred to as being “above” or “below” another element, the element may be “directly” located “above” or “below” the other element or there may be intermediate elements.

[0083] (3) Where there is no conflict, the embodiments of this disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

[0084] The above description is merely an exemplary embodiment of this disclosure and is not intended to limit the scope of protection of this disclosure, which is determined by the appended claims.

Claims

1. A flexible capacitive tactile sensor, comprising: A first flexible electrode layer, on which a first electrode array is disposed; A second flexible electrode layer, on which a second electrode array is disposed; An ion gel film dielectric layer is disposed between a first flexible electrode layer and a second flexible electrode layer, and the surface of the ion gel film dielectric layer has a microstructure, wherein the distance between the contact area of ​​the first electrode array or the second electrode array and the ion gel film dielectric layer is at the nanometer level. Under pressure, the contact area of ​​the electrode-electrolyte interface formed between the dielectric layer of the ion gel film and the first electrode array or the second electrode array increases due to the deformation of the microstructure. in, The first electrode array and the second electrode array are arranged opposite to each other. At least one of the multiple electrodes in the first electrode array or the second electrode array has a length of a first length in a first direction and a length of a second length in a second direction. The first direction is perpendicular to the second direction. The first length and the second length are less than 5 mm, and the spacing between adjacent electrodes is less than 5 mm. Each electrode in the first electrode array and the second electrode array has a separate lead, which is arranged in the intervals between the electrodes; The leads of two electrodes arranged opposite each other in the first electrode array and the second electrode array do not intersect in the direction in which the two electrodes overlap. Of the four electrodes located at the center of the first electrode array and the second electrode array, the leads of two electrodes are led out in opposite directions along the first axis, and the leads of the other two electrodes are led out in opposite directions along the second axis, with the first axis perpendicular to the second axis. The first flexible electrode layer includes a first flexible thin film layer, and the first electrode array is fabricated as a patterned aluminum thin film on the first flexible thin film layer by electron beam evaporation; and The second flexible electrode layer includes a second flexible thin film layer, and the second electrode array is fabricated as a patterned aluminum thin film on the second flexible thin film layer by electron beam evaporation.

2. The flexible capacitive tactile sensor as described in claim 1, wherein, The dielectric layer of the ion gel film is composed of a polymer and an ionic liquid, wherein the polymer includes poly(vinylidene fluoride-hexafluoropropylene) and the ionic liquid includes 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

3. A method for fabricating a flexible capacitive tactile sensor, comprising: A first flexible electrode layer is prepared, on which a first electrode array is disposed; To prepare an ion gel film dielectric layer, the ion gel film dielectric layer is placed on a first flexible electrode layer. The preparation of the ion gel film dielectric layer includes: preparing a mixed solution of a polymer and an ionic liquid; pouring the mixed solution onto a microstructure template; and curing the mixed solution to obtain the ion gel film dielectric layer. A second flexible electrode layer is prepared, on which a second electrode array is disposed; The second flexible electrode layer is placed on top of the dielectric layer of the ion gel film; The first flexible electrode layer, the ion gel film dielectric layer and the second flexible electrode layer are encapsulated to form the flexible capacitive tactile sensor, wherein the distance between the contact area of ​​the first electrode array or the second electrode array and the ion gel film dielectric layer is at the nanometer level. Under pressure, the contact area of ​​the electrode-electrolyte interface formed between the dielectric layer of the ion gel film and the first electrode array or the second electrode array increases due to the deformation of the microstructure. in, The first electrode array and the second electrode array are arranged opposite to each other. At least one of the multiple electrodes in the first electrode array or the second electrode array has a length of a first length in a first direction and a length of a second length in a second direction. The first direction is perpendicular to the second direction. The first length and the second length are less than 5 mm, and the spacing between adjacent electrodes is less than 5 mm. Each electrode in the first electrode array and the second electrode array has a separate lead, which is arranged in the intervals between the electrodes; The leads of two electrodes arranged opposite each other in the first electrode array and the second electrode array do not intersect in the direction in which the two electrodes overlap. Of the four electrodes located at the center of the first electrode array and the second electrode array, the leads of two electrodes are led out in opposite directions along the first axis, and the leads of the other two electrodes are led out in opposite directions along the second axis, with the first axis perpendicular to the second axis. The preparation of the first flexible electrode layer and the second flexible electrode layer further includes: A patterned aluminum thin film is deposited on the first flexible thin film layer of the first flexible electrode layer using electron beam evaporation as a first electrode array, and a patterned aluminum thin film is deposited on the second flexible thin film layer of the second flexible electrode layer using electron beam evaporation as a second electrode array.

4. The method for fabricating the flexible capacitive tactile sensor as described in claim 3, wherein, The prepared polymer-ionic liquid mixture solution further includes: The polymer is dissolved in the solution to form a first mixed solution; Use a magnetic stirrer to stir the first mixture until it becomes clear; An ionic liquid is added to the clarified first mixed solution to form a second mixed solution; and The second mixed solution is stirred with a magnetic stirrer until it becomes clear, forming the mixed solution.

5. The method for fabricating the flexible capacitive tactile sensor as described in claim 4, wherein, The polymer comprises poly(vinylidene fluoride-hexafluoropropylene), and the ionic liquid comprises 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; The mass ratio of the polymer to the solution is 1:1 to 1:20; and The mass ratio of the ionic liquid to the polymer is 1:2 to 6:

1.

6. The method for fabricating the flexible capacitive tactile sensor as described in claim 3, wherein, The first flexible film layer and the second flexible film layer are composed of at least one of the following materials: thermoplastic polyurethane elastomer rubber (TPU), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), nylon 6 (PA6), polylactic acid (PLA), polyacrylonitrile (PAN), and polyethersulfone (PES).

7. A tactile sensing system, comprising: The excitation circuit is configured to output a sensing excitation signal to one or more electrodes in the first flexible electrode layer and the second flexible electrode layer. The flexible capacitive tactile sensor as described in any one of claims 1-2 is configured to determine a touch sensing signal based on the sensing excitation signal according to the change in the contact area between at least one of the first flexible electrode layer and the second flexible electrode layer and the dielectric layer of the ion gel film. A signal detection circuit is configured to receive a touch sensing signal from the flexible capacitive tactile sensor. A signal processor is configured to process the touch sensing signal and determine the touch location and touch force.

8. An electronic device, comprising: Tactile sensing detection surface A flexible capacitive tactile sensor as described in any one of claims 1-2 is attached to the tactile sensing detection surface.

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