A flexible sensor that senses complex deformations

Abstract

The present application discloses a flexible sensor for sensing complex deformation, comprising: a flexible substrate, on which at least four microchannels distributed along its axial direction are opened; any one of the microchannels is arranged at the center of the flexible substrate; a flexible electrode is arranged in the microchannel; and a wire is connected to the flexible electrode for connecting to the required measurement circuit. The present application is designed to open a microchannel in the center of the flexible substrate, and the remaining microchannels are arranged around along its axis, and flexible electrodes are arranged in the microchannel, and wires are connected to the ends of the flexible electrodes, and connected to the required measurement circuit by using the wires; combining the sensing characteristics of multiple microchannels, it can detect the tensile bending coupling deformation, and identify the azimuth of the bending deformation to realize the bending direction detection; and realize the perception of complex deformation.

Description

Technical Field

[0001] The present disclosure generally relates to the field of flexible sensor technology, and more particularly to a flexible sensor capable of sensing complex deformations. Background Art

[0002] Flexible sensors are made of flexible materials. Compared with traditional rigid sensors, flexible sensors have good flexibility, ductility, adaptability, and biocompatibility. Flexible sensors have broad application prospects in health monitoring, motion monitoring, medical rehabilitation, and soft robotics. At present, there are many types of flexible sensors that can sense single deformation, but there are also many complex deformations in actual engineering problems, such as coupled deformation of stretching and bending. The problem of complex deformation perception has not been well solved. In addition, existing bending sensors mainly detect bending angles, ignoring the important information of bending direction.

[0003] Therefore, it is very necessary to study a flexible sensor that can sense complex deformations. Summary of the invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a flexible sensor that is simple in structure and easy to implement and can sense complex deformations.

[0005] In a first aspect, the present application provides a flexible sensor for sensing complex deformation, comprising:

[0006] A flexible substrate, on which at least four microchannels distributed along its axial direction are provided; any one of the microchannels is arranged at the center of the flexible substrate;

[0007] A flexible electrode is disposed in the microfluidic channel;

[0008] A wire is connected to the flexible electrode and is used to connect to a desired measurement circuit.

[0009] According to the technical solution provided in the embodiment of the present application, the cross-sectional shape of the flexible substrate is circular, elliptical, triangular, rectangular or polygonal.

[0010] According to the technical solution provided in the embodiment of the present application, the cross-sectional shape of the microchannel is circular, triangular or quadrilateral.

[0011] According to the technical solution provided in the embodiment of the present application, the flexible substrate is made of polydimethylsiloxane (PDMS), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), polyurethane (PU), hydrogel, natural rubber, vulcanized rubber or silicone-based rubber.

[0012] According to the technical solution provided in the embodiment of the present application, the flexible electrode is formed by a conductive liquid.

[0013] According to the technical solution provided in the embodiment of the present application, the conductive liquid is liquid metal, ion gel or ionic liquid.

[0014] In summary, the present application specifically discloses a specific structure of a flexible sensor for sensing complex deformation. The cross-sectional shape of the flexible substrate of the present application can be circular, elliptical, triangular, rectangular, polygonal, etc. A microchannel is opened in the center of the flexible substrate, and the remaining microchannels are evenly distributed around along its axial direction. Flexible electrodes are arranged in the microchannels, and wires are connected to the ends of the flexible electrodes, and the wires are connected to the required measurement circuits; when the flexible substrate of the sensor is deformed, the resistance of the flexible electrodes in the microchannels will change accordingly, so as to detect the deformation. The central microchannel is used to detect the overall tensile deformation; the difference between the deformation of the peripheral microchannels and the central microchannel is used to detect the bending angle; at the same time, when bending deformation occurs, the deformation of the microchannels in each direction is different, which is used to detect the bending direction; through the position distribution of the central microchannel and the peripheral microchannels, the detection of complex deformations of pulling and bending coupling can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0016] Figure 1 Schematic diagram of the structure of a flexible sensor that can sense complex deformations.

[0017] Figure 2 Schematic diagram of the changes in the microfluidic channel of the flexible sensor under tensile deformation.

[0018] Figure 3 Schematic diagram of the flexible sensor detecting tensile and bending coupled deformation.

[0019] Figure 4 Schematic diagram of the molding mold assembly for preparing flexible sensors.

[0020] Figure 5 Side view of the molding die assembly diagram for preparing flexible sensors.

[0021] Figure 6 It is a schematic diagram of the upper mold structure of the forming mold.

[0022] Figure 7 Schematic diagram of the microchannel and the bending angle.

[0023] Numbers in the figure: 1, flexible substrate; 2, flexible electrode; 3, upper mold; 4, lower mold; 5, metal wire; 6, fixed micropore; 7, injection hole. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] Embodiment 1

[0027] Please refer to Figure 1 The schematic diagram of the structure of a flexible sensor for sensing complex deformation provided by the present application includes:

[0028] The flexible substrate 1 has a cross-sectional shape that can be circular, elliptical, triangular, rectangular, polygonal, etc. The flexible substrate 1 is provided with at least four microfluidic channels, and one microfluidic channel is provided in the center of the flexible substrate 1, and the remaining microfluidic channels are evenly distributed around the flexible substrate 1 along its axis direction;

[0029] Here, the flexible substrate 1 is made of polydimethylsiloxane (PDMS), polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), polyethylene naphthalate (PEN), polyurethane (PU), hydrogel, natural rubber, vulcanized rubber, silicone-based rubber, etc.; the cross-sectional shape of the microchannel is circular, triangular, quadrilateral, etc.;

[0030] A flexible electrode 2 is arranged in the microfluidic channel;

[0031] The flexible electrode 2 is formed by a conductive liquid; the type of the conductive liquid here is, for example, liquid metal, ion gel or ionic liquid.

[0032] The wire is connected to the flexible electrode 2 and is used to connect to a required measurement circuit.

[0033] The preparation method of the flexible sensor is as follows:

[0034] like Figure 6 As shown, the upper mold 3 and the lower mold 4 are printed using 3D printing technology. Figure 4 As shown, the upper mold 3 and the lower mold 4 are assembled, as shown in FIG. Figure 5As shown, a plurality of fixed micropores 6 and an injection hole 7 are formed between the upper mold 3 and the lower mold 4, and the fixed micropores 6 are arranged around the injection hole 7; the metal wire 5 is inserted into the fixed micropore 6, and the PDMS, PVA, PI and other materials are poured into the mold through the injection hole 7. After the pouring is completed, the metal wire 5 is inserted into the injection hole 7, and after waiting for complete solidification, the metal wire 5 is pulled out, and the upper and lower molds are removed to obtain a flexible substrate 1 with a microchannel, and liquid metal is injected into the microchannel, and the wire is led out, so that a flexible sensor with 9 microchannels (1 in the center and 8 evenly arranged around) can be obtained, as shown in FIG. Figure 1 shown.

[0035] This flexible sensor can be applied to human joints or in the field of soft robots to detect stretching, bending, and coupled deformation of stretching and bending, and to realize the perception of complex deformation.

[0036] Specifically,

[0037] When the flexible sensor is stretched and deformed, Figure 2 As shown, the cross-sectional area and length of the microchannel will change. The volume V of the flexible electrode injected into the microchannel does not change before and after deformation. When the flexible substrate 1 is stretched and deformed, the length of the microchannel increases, the cross-sectional area decreases, and the resistance of the flexible electrode 2 changes accordingly.

[0038] V=L0S0=L′S′ (1)

[0039] Wherein, V is the volume of the flexible electrode in the microfluidic channel, L0 and L′ are the lengths of the microfluidic channel before and after deformation, and S0 and S′ are the cross-sectional areas of the microfluidic channel before and after deformation.

[0040]

[0041] Wherein, R is the resistance of the flexible electrode 2 in the microchannel, ρ is the resistivity of the flexible electrode 2, L is the length of the microchannel, and S is the cross-sectional area of ​​the microchannel.

[0042] By using the changes in the cross-sectional area and length of the central microchannel, the resistance value at any stretching length can be obtained from formula (2), and the overall stretching deformation of the sensor can be detected.

[0043] When the flexible sensor undergoes tension and bending coupling deformation, Figure 3As shown in the figure, the bending angle of the flexible sensor is θ. The two microchannels in the positive and negative directions of the bending direction are analyzed. The bending radius and microchannel length in the negative bending direction are defined as r1 and l1 respectively, and the bending radius and microchannel length in the positive bending direction are defined as r2 and l2 respectively. Because r1>r2, it can be seen from formulas (3) and (4) that l1>l2. Therefore, the deformation in the negative direction of the bending direction is the largest, and the resistance change rate is the largest; conversely, the deformation in the positive direction of the bending direction is the smallest, and the resistance change rate is the smallest. The bending direction is detected by utilizing the different deformations of the microchannels evenly distributed around the sensor when the sensor is bent. The central microchannel is the neutral axis of the sensor. When the sensor is subjected to the coupling deformation of pulling and bending, the central microchannel only has the tensile deformation, and no bending deformation occurs. The microchannels evenly distributed around the sensor are subjected to the coupling deformation of pulling and bending. The difference between the deformation of the peripheral microchannels and the deformation of the central microchannel is the deformation of the bending. By measuring the resistance change rate at different bending angles as a reference value, the bending angle can be obtained by selecting the minimum resistance change rate and comparing it with the reference value. Therefore, this sensor can realize the perception of coupled deformation of pulling and bending, and can also detect the bending direction.

[0044] l1=θr1 (3)

[0045] l2=θr2 (4)

[0046] Among them, θ is the bending angle of the flexible sensor, r1 and r2 are the bending radii, and l1 and l2 are the lengths of the microchannel.

[0047] Take 9 microchannels as an example. Figure 7 As shown in the figure, the microchannels are set as microchannel 0, microchannel 1, microchannel 2, microchannel 3, microchannel 4, microchannel 5, microchannel 6, microchannel 7, and microchannel 8; the direction of microchannel 1 is set as the direction of the bending azimuth angle 0°, microchannel 0 is at the center of the sensor, and the 8 evenly arranged microchannels correspond to Figure 7 There are 8 azimuth angles (0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°), namely, microchannel 1 is arranged at 0°, microchannel 2 is arranged at 45°, microchannel 3 is arranged at 90°, microchannel 4 is arranged at 135°, microchannel 5 is arranged at 180°, microchannel 6 is arranged at 225°, microchannel 7 is arranged at 270°, and microchannel 8 is arranged at 315°;

[0048] The deformation amounts of microchannels 0 to 8 are defined as: △ε0, △ε1, △ε2, △ε3, △ε4, △ε5, △ε6, △ε7, and △ε8, respectively.

[0049] When the sensor is bent and deformed, take the bending angle θ and the bending azimuth angle 0° as an example: according to the symmetry, the deformation of microchannels 3 and 7, microchannels 4 and 6, and microchannels 2 and 8 are the same (△ε3=△ε7, △ε4=△ε6, △ε2=△ε8), and the deformation of microchannel 1 is the smallest, and the deformation of microchannel 5 is the largest;

[0050] If the bending angle is θ and the bending azimuth angle is 22.5°: According to symmetry, the deformation of microchannels 1 and 2, microchannels 3 and 8, microchannels 4 and 7, and microchannels 5 and 6 are the same (△ε1=△ε2, △ε3=△ε8, △ε4=△ε7, △ε5=△ε6), and the deformation of microchannels 1 and 2 is the smallest, and the deformation of microchannels 5 and 6 is the largest;

[0051] If the bending angle is θ and the bending azimuth angle is 15°: the deformation of microchannel 1 is the smallest, and the deformation of microchannel 5 is the largest. Then the position of the microchannel 1 is determined based on the deformation of microchannels 2 and 8 on both sides of microchannel 1, and microchannels 4 and 6 on both sides of microchannel 5. The bending azimuth angle is 15°, and the size relationship should be △ε2<△ε8, △ε4<△ε6. If the bending azimuth angle is not a multiple of 15°, the azimuth angle can also be calculated through geometric relationships.

[0052] When the sensor undergoes tensile and bending coupled deformation, the overall tensile deformation of the sensor is detected through microchannel 0, and the difference in deformation between microchannels 1 to 8 and microchannel 0 is used to detect the bending angle and bending direction, thereby achieving complex perception of tensile and bending coupled deformation.

[0053] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

Claims

1. A flexible sensor for sensing complex deformation, characterized in that: include: A flexible substrate (1), wherein the flexible substrate (1) is provided with at least four microchannels distributed along its axial direction; Any one of the microchannels is arranged at the center of the flexible substrate (1); A flexible electrode (2) is arranged in the microchannel; the flexible electrode (2) is formed by a conductive liquid; A wire connected to the flexible electrode (2) and used for connecting to a desired measurement circuit; When the flexible substrate (1) is stretched and deformed, the length of the microchannel increases and the cross-sectional area decreases, and the resistance of the flexible electrode (2) changes accordingly; When the flexible sensor undergoes a pulling and bending coupling deformation, the tensile deformation of the flexible sensor as a whole is detected by a microchannel located at the center of the flexible substrate (1), and the bending angle and bending direction of the flexible sensor are detected by the difference between the deformation amount generated by the microchannel located around the central axis of the flexible substrate (1) and the deformation amount generated by the microchannel located at the center of the flexible substrate (1); The deformation is the largest in the opposite direction of the bending direction, and the resistance change rate is the largest. The deformation is the smallest in the positive direction of the bending direction, and the resistance change rate is the smallest. When the flexible sensor is bent and deformed, the deformation of the microchannels evenly distributed around it is different, so the bending direction can be detected. The microfluidic channel located at the center of the flexible substrate (1) is the neutral axis. When the flexible sensor undergoes a pulling and bending coupled deformation, the neutral axis undergoes only a pulling deformation and no bending deformation occurs, while the microfluidic channels uniformly distributed around the sensor undergo a pulling and bending coupled deformation. The difference between the deformation of the peripheral microfluidic channels and the deformation of the neutral axis is the bending deformation. The bending angle can be obtained by measuring the resistance change rate at different bending angles as a reference value and selecting the minimum resistance change rate for comparison with the reference value. The upper mold (3) and the lower mold (4) are assembled, and a plurality of fixed micropores (6) and an injection hole (7) are formed between the upper mold (3) and the lower mold (4), and the fixed micropores (6) are arranged around the injection hole (7); the metal wires (5) are inserted into the fixed micropores (6), and the flexible substrate (1) is poured into the mold through the injection hole (7); after the pouring is completed, the metal wires (5) are inserted into the injection hole (7), and after waiting for complete solidification, the metal wires (5) are pulled out, and the upper and lower molds are removed to obtain a flexible substrate (1) with microchannels; liquid metal is injected into the microchannels, and the wires are led out to obtain a flexible sensor with 9 microchannels.

2. The flexible sensor for sensing complex deformation according to claim 1, characterized in that: The cross-sectional shape of the flexible substrate (1) is circular, elliptical, triangular, rectangular or polygonal.

3. The flexible sensor for sensing complex deformation according to claim 1, characterized in that: The cross-sectional shape of the microchannel is circular, triangular or quadrilateral.

4. The flexible sensor for sensing complex deformation according to claim 1, characterized in that: The flexible substrate (1) is made of polydimethylsiloxane, polyvinyl alcohol, polyethylene terephthalate, polyimide, polyethylene naphthalate, polyurethane, hydrogel, natural rubber, vulcanized rubber or silicone-based rubber.

5. The flexible sensor for sensing complex deformation according to claim 1, characterized in that: The conductive liquid is liquid metal, ion gel or ionic liquid.

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