Flexible pressure sensor and preparation method thereof

Abstract

The invention relates to a flexible pressure sensor and a preparation method thereof. The preparation method of the flexible pressure sensor comprises the steps of providing a flexible conductive substrate, etching one surface of the flexible conductive substrate by adopting first laser to form a first microstructure with the same height, and then etching the side wall of the first microstructure by adopting second laser to form a hierarchical microstructure with at least one annular groove, a first flexible substrate is obtained; providing a second flexible substrate, wherein the second flexible substrate comprises a second flexible substrate and an electrode arranged on one surface of the second flexible substrate; and arranging a second flexible substrate on the first flexible substrate in a laminated manner, and enabling an electrode to be in contact with the hierarchical microstructure, thereby obtaining the flexible pressure sensor. The flexible pressure sensor prepared by the preparation method not only can maintain high sensitivity, but also has a wide detection range, and can maintain a good linear relation of output signals.

Description

Technical Field

[0001] The present invention relates to the field of flexible electronic technology, and in particular to a flexible pressure sensor and a preparation method thereof. Background Art

[0002] Microstructure design is an effective way to improve the performance of flexible pressure sensors. In traditional flexible pressure sensors, microstructures are mainly prepared by silicon mold etching, magnetron sputtering, oxygen plasma treatment, 3D printing and other methods. Not only are the steps complicated and the materials are many, but the process parameters are also difficult to control. At the same time, it is difficult for traditional flexible pressure sensors to maintain high sensitivity while also having a wide detection range.

[0003] Although there are methods on the market to improve the sensitivity of pressure sensors and increase the measurement range by preparing microstructures of different heights, it is difficult for the output signal to maintain a linear relationship within the entire measurement range. This is mainly because the compressibility of the microstructure gradually decreases as the pressure increases. Summary of the invention

[0004] Based on this, it is necessary to provide a flexible pressure sensor and a preparation method thereof to address the above problems. The preparation method has the advantages of simple process, low cost, environmental protection and no pollution, and is suitable for large-scale industrial production. The prepared flexible pressure sensor can not only maintain high sensitivity while having a wide detection range, but also can maintain a good linear relationship in the output signal.

[0005] A method for preparing a flexible pressure sensor, comprising:

[0006] Providing a flexible conductive substrate, using a first laser to etch a surface of the flexible conductive substrate to form a plurality of first microstructures of the same height, and then using a second laser to etch the sidewalls of the first microstructures to form a hierarchical microstructure having at least one annular groove, thereby obtaining a first flexible substrate;

[0007] Providing a second flexible substrate, wherein the second flexible substrate comprises a second flexible substrate and an electrode disposed on a surface of the second flexible substrate;

[0008] The second flexible substrate is stacked on the first flexible substrate, and the electrode is in contact with the hierarchical microstructure to obtain a flexible pressure sensor.

[0009] In one embodiment, a cross-sectional width of the first microstructure gradually decreases along a direction in which the first microstructure moves away from the flexible conductive substrate.

[0010] In one embodiment, when the number of annular grooves is at least two, with the direction from the groove mouth to the groove bottom as the depth direction, the depth of adjacent annular grooves tends to gradually decrease or gradually increase from the side of the hierarchical microstructure close to the flexible conductive substrate to the side away from the flexible conductive substrate.

[0011] In one embodiment, when the number of the annular grooves is at least two, the depth direction is from the groove opening to the groove bottom of the annular groove, and the depths of adjacent annular grooves are the same.

[0012] In one embodiment, the depth of the annular groove is 10 μm-500 μm, and the width of the annular groove is 5 μm-200 μm.

[0013] In one embodiment, when the number of the annular grooves is at least two, during the second laser etching process, the annular grooves are sequentially and spaced apart from each other on the side walls of the first microstructure from the bottom surface of the first microstructure toward a direction away from the bottom surface of the flexible conductive substrate.

[0014] In one embodiment, when the number of the annular grooves is at least two, the distances between adjacent annular grooves are the same;

[0015] And / or, when the number of the annular grooves is at least two, the distance between adjacent annular grooves is 5 μm-50 μm;

[0016] And / or, the distance between the annular groove closest to the bottom surface of the hierarchical microstructure and the bottom surface of the hierarchical microstructure is 5 μm-50 μm.

[0017] In one embodiment, during the second laser etching process, the etching path is parallel to the bottom surface of the first microstructure.

[0018] In one embodiment, the height of the first microstructure is 10 μm-500 μm;

[0019] And / or, when the bottom surface of the first microstructure is a square, the side length of the bottom surface of the first microstructure is 20 μm-1000 μm.

[0020] A flexible pressure sensor, comprising:

[0021] A first flexible substrate, comprising a flexible conductive substrate and a hierarchical microstructure disposed on a surface of the flexible conductive substrate, wherein the flexible conductive substrate and the hierarchical microstructure are an integral structure, and a side wall of the hierarchical microstructure has at least one annular groove;

[0022] The second flexible substrate comprises a flexible substrate and an electrode disposed on a surface of the flexible substrate. The second flexible substrate is stacked with the first flexible substrate, and the electrode is in contact with the hierarchical microstructure.

[0023] In the preparation method of the present invention, laser etching is directly used to etch the surface of the flexible conductive substrate to form a hierarchical microstructure, which has a simple process, low cost, environmental protection and no pollution, and can be mass-produced industrially. At the same time, the side wall of the obtained hierarchical microstructure has at least one annular groove, so that the hierarchical microstructure has at least 2 levels, and the microstructure with multiple levels has a high degree of variability, so that the prepared flexible pressure sensor can improve the detection range and reliability while improving the sensitivity. At the same time, due to the presence of the annular groove, the hierarchical microstructure is similar to a spring structure, which effectively increases the compressibility of the hierarchical microstructure and avoids the problem that the compressibility of the hierarchical microstructure decreases with the increase of pressure, thereby making the output signal of the sensor have a good linear relationship in the entire pressure range.

[0024] Specifically, under the action of pressure, the first layer located at the highest point in the hierarchical microstructure deforms first, so that the contact area between the hierarchical microstructure and the electrode increases, the conductive path of the sensor increases, and the sensitivity is high. As the pressure increases, the second layer, the third layer and other layers with the next highest height will contact each other and contact the electrodes in turn, further increasing the conductive path of the sensor and maintaining the sensitivity of the sensor. At the same time, due to the presence of annular grooves between adjacent levels, the compressibility between adjacent levels is increased, thereby enhancing the compressibility of the hierarchical microstructure, avoiding the problem that the compressibility of the hierarchical microstructure decreases with the increase of pressure. Therefore, the hierarchical microstructure can increase the saturated contact area of ​​the sensor, increase the conductive path, and extend its pressure linear response range, thereby improving the sensitivity of the sensor while improving the detection range and reliability, and making the output signal in the entire pressure range present a good linear relationship, which is convenient for the later analysis and processing of the signal data in the sensor, and further improves the accuracy of the measurement data. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A prefabricated graphic of an embodiment;

[0026] Figure 2 for Figure 1 A schematic diagram of a first microstructure corresponding to the prefabricated pattern shown;

[0027] Figure 3 is a schematic diagram of a first flexible substrate according to Embodiment 3 of the present invention;

[0028] Figure 4 It is a structural schematic diagram of the flexible pressure sensor of the present invention;

[0029] Figure 5 is a schematic diagram of a first flexible substrate of Comparative Example 3 of the present invention;

[0030] Figure 6 is a curve diagram showing the relationship between the current change rate and the pressure of the flexible pressure sensor according to Example 3 of the present invention;

[0031] Figure 7 A curve diagram showing the relationship between the current change rate and the pressure of the flexible pressure sensor of Comparative Example 1 of the present invention;

[0032] Figure 8 This is a curve diagram of the relationship between the current change rate and pressure of the flexible pressure sensor of comparative example 2 of the present invention.

[0033] In the figure: 1. flexible conductive substrate; 2. first microstructure; 3. hierarchical microstructure; 4. annular groove; 5. first flexible substrate; 6. second flexible substrate. DETAILED DESCRIPTION

[0034] The flexible pressure sensor and the preparation method thereof provided by the present invention will be further described below.

[0035] The present invention provides a method for preparing a flexible pressure sensor, comprising:

[0036] S1, providing a flexible conductive substrate, and using a first laser to etch a surface of the flexible conductive substrate to form Figure 2 Then, a second laser is used to etch the sidewalls of the first microstructures to form a hierarchical microstructure having at least one annular groove, and a first microstructure having a plurality of first microstructures at the same height is obtained. Figure 3 The first flexible substrate shown;

[0037] S2. providing a second flexible substrate, wherein the second flexible substrate comprises a second flexible substrate and an electrode disposed on a surface of the second flexible substrate;

[0038] S3. Laminating the second flexible substrate on the first flexible substrate and making the electrode contact the hierarchical microstructure to obtain a flexible pressure sensor.

[0039] In one embodiment, the thickness of the flexible conductive substrate is 50 μm-200 μm.

[0040] In step S1, the method for preparing the flexible conductive substrate is as follows:

[0041] S11, providing a flexible conductive mixed liquid;

[0042] S12, spin coating the flexible conductive mixed liquid on a carrier, and curing the mixture to obtain the flexible conductive substrate.

[0043] In one embodiment, in step S11, the flexible conductive mixed solution is mixed with polymer monomers, conductive materials and curing agents, wherein the mass fraction of the conductive materials in the flexible conductive mixed solution is 5%-20%. This configuration enables the flexible conductive substrate to have excellent conductivity, thermal stability and biocompatibility.

[0044] Preferably, the mass ratio of the polymer monomer to the curing agent is 10:(0.9-1.1). Further preferably, the mass ratio of the polymer monomer to the curing agent is 10:1. With such an arrangement, the flexible conductive substrate has excellent tensile properties.

[0045] Furthermore, the material of the polymer monomer is selected from at least one of polydimethylsiloxane, polyurethane elastomer, and polytrimethylene carbonate. Since polydimethylsiloxane has the best biocompatibility and thermal stability, polydimethylsiloxane is preferred in the present invention. This arrangement further improves the flexibility of the flexible conductive substrate.

[0046] The conductive material is selected from at least one of carbon nanotubes, graphene, and silver nanowires, so that the flexible conductive substrate has excellent flexibility while improving the conductivity of the flexible conductive substrate. In the present application, the conductive material is preferably carbon nanotubes.

[0047] Furthermore, step S11 further includes removing bubbles in the flexible conductive mixed solution to avoid forming holes in the flexible conductive substrate. Specifically, the method for removing bubbles may be: placing the mixture under a vacuum condition of 0.1 Torr-1 Torr for 10 min-30 min.

[0048] In step S12, the carrier is preferably a glass substrate, the spin coating speed is 50 rpm-2000 rpm, the spin coating time is 10 s-30 s, the curing temperature is 25°C-150°C, and the curing time is 0.25h-24h. This arrangement facilitates the control of the thickness and molding efficiency of the flexible conductive substrate.

[0049] Before the first laser etching, a prefabricated pattern is drawn using computer software such as CAD, and then the drawn prefabricated pattern is imported into the software of the laser etching equipment, so that the laser scans the flexible conductive substrate according to the drawn prefabricated pattern to etch the hierarchical microstructure.

[0050] Specifically, Figure 1As shown in the figure, the prefabricated grid pattern is drawn using CAD software. In the figure, area B and area C are filled with lines respectively, and the spacing between the lines is equal. Area B and area C do not cross. After the prefabricated grid pattern is imported into the software of the laser etching equipment, during laser etching, the laser scans along the filled lines. Area B and area C are laser scanned once, and area A is not laser scanned. The etching result is as follows Figure 2 The first microstructure 2 shown, Figure 2 In the figure, there are multiple first microstructures 2 with the same height.

[0051] In one embodiment, the flexible conductive substrate 1 is placed on an angle-adjustable processing platform, and laser etching equipment is used to perform laser etching on it. When etching the first microstructure 2, the laser is perpendicular to the flexible conductive substrate 1. When the second laser is etched, the angle of the processing platform is adjusted to adjust the angle between the flexible conductive substrate 1 and the laser etching path, and then at least one annular groove 4 is etched on the side wall of the first microstructure 2 to obtain the following: Figure 3 The hierarchical microstructure 3 is shown.

[0052] At the same time, in the present invention, the shape and height of the microstructure can be controlled by the drawn prefabricated graphics and the filling of the lines in the prefabricated graphics, and the method is simple and easy to operate.

[0053] In one embodiment, the cross-sectional width of the first microstructure gradually decreases along the direction in which the first microstructure is away from the flexible conductive substrate. For example, if the cross-sectional shape of the first microstructure is a cone, a hemisphere, a trapezoid, etc., preferably, the first microstructure with a cone cross-sectional shape may be a quadrangular pyramid or a triangular pyramid, and the first microstructure with a trapezoid cross-sectional shape may be a quadrangular pyramid. Thus, the hierarchical microstructure is easy to deform under the action of pressure, and the contact area between the hierarchical microstructure and the electrode can gradually increase with the increase of pressure, with fast response and high sensitivity.

[0054] In step S1, during the first laser etching, the pulse energy of the laser output forms a high-energy beam after passing through a reflector and a focusing mirror and acts on the surface of the flexible conductive substrate, gasifying or decomposing the surface material of the flexible conductive substrate through photochemical action to form the first microstructure.

[0055] Furthermore, in order to cause photochemical action on the surface of the flexible conductive substrate and reduce thermal effects, the wavelength of the laser during laser etching is less than or equal to 355 nm, and the laser pulse width is less than or equal to picoseconds.

[0056] In addition, the depth and efficiency of the first laser etching and the second laser etching can be controlled by adjusting the single pulse energy and scanning rate of the laser.

[0057] For example, when the single pulse energy of the laser is less than 1 μJ, the etching depth is small and multiple etchings are required, which affects efficiency. When the single pulse energy of the laser is greater than 200 μJ, the etching depth is large and the tensile strength of the flexible conductive substrate is greatly reduced, affecting its use. Therefore, the single pulse energy of the laser is preferably 1 μJ-200 μJ.

[0058] When the laser scanning speed is less than 50mm / s, the etching time is long and the efficiency is low; when the laser scanning speed is greater than 3000mm / s, the laser spot is not overlapped and the microstructure quality is low, so the laser scanning speed is preferably 50mm / s-3000mm / s. Therefore, in the present invention, preferably, the conditions of the first laser etching and the second laser etching are: the laser wavelength is less than or equal to 355nm, the laser single pulse energy is 1μJ-200μJ, and the laser scanning speed is 50mm / s-3000mm / s.

[0059] It should be noted that in the present invention, the direction from the groove opening to the groove bottom of the annular groove is the depth direction, and the laser etching depth direction or the depth direction of the annular groove is Figure 3 Meanwhile, the direction close to the bottom surface of the hierarchical microstructure to the direction away from the bottom surface of the flexible conductive substrate is the width direction, that is, the width direction of the laser etching or the width direction of the annular groove in the present invention is Figure 3 In the direction indicated by arrow B.

[0060] As the number of annular grooves on the side wall of the hierarchical microstructure increases, the compressibility of the hierarchical microstructure increases. Therefore, in the present invention, preferably, the number of the annular grooves is at least two.

[0061] At the same time, considering that the depth difference of the annular grooves of adjacent layers will affect the compressibility of the hierarchical microstructure, and further affect the sensitivity and range of the sensor, the present invention preferably, when the number of annular grooves is at least two, the depth direction is the direction from the notch of the annular groove to the bottom of the groove, and the depth of the adjacent annular grooves is gradually decreasing or gradually increasing from the side of the hierarchical microstructure close to the flexible conductive substrate to the side away from the flexible conductive substrate. In this way, as the pressure increases, the compressibility difference of adjacent layers in the hierarchical microstructure is obvious, and then the sensitivity of the sensor changes continuously, thereby effectively improving the sensitivity and range of the sensor, and is conducive to the linearity of the output signal of the sensor within the entire measurement range.

[0062] Further preferably, the depth of the adjacent annular grooves gradually decreases from the bottom of the hierarchical microstructure toward the direction away from the flexible conductive substrate. Such an arrangement will gradually increase the depth of the annular grooves from top to bottom, that is, the depth of the annular grooves close to the bottom of the hierarchical microstructure is the largest, so that the compressibility of each layer from top to bottom increases successively, making the compressibility of the hierarchical microstructure stronger, which is convenient for offsetting the problem of the gradual decrease in the deformation of the hierarchical microstructure as the pressure increases, thereby making the sensor better at maintaining the linear output signal within the entire measurement range.

[0063] In one embodiment, when the number of the annular grooves is at least two, the direction from the groove opening to the groove bottom of the annular groove is the depth direction, and the depths of adjacent annular grooves are the same.

[0064] It is understandable that the depth of the annular groove in the present invention depends on the depth of etching during the second laser etching process, and the width of the annular groove depends on the width of etching during the second laser etching process. Therefore, the depth and width of the annular groove can be adjusted by adjusting the etching depth and etching width of the laser.

[0065] In step S1, the present invention preferably, when the number of the annular grooves is at least two, in the second laser etching process, the etching depth is 10μm-500μm, and the etching width is 5μm-200μm, so that the depth of the annular groove on the side wall of the hierarchical microstructure is 10μm-500μm, and the width of the annular groove is 5μm-200μm, which is convenient for improving the compressibility of the hierarchical microstructure, improving its deformability, and thereby improving the sensitivity of the sensor and the range of measurement, while maintaining the linearity of the output signal within the entire measurement range.

[0066] Furthermore, when the number of the annular grooves is at least two, during the second laser etching process, the annular grooves are sequentially and spaced apart from each other on the sidewall of the first microstructure from the bottom surface of the first microstructure toward the direction away from the bottom surface of the flexible conductive substrate. This arrangement facilitates improving the linear measurement range of the sensor.

[0067] In order to better maintain the linearity of the output signal of the sensor within the entire measuring range, the present invention preferably adopts equal-pitch etching when the number of the annular grooves is at least two, so that the distances between adjacent annular grooves are the same.

[0068] At the same time, in order to improve the sensitivity of the sensor and increase the measuring range, preferably, when the number of the annular grooves is at least two, the distance between adjacent annular grooves is 5 μm-50 μm.

[0069] It can be understood that the distance between adjacent annular grooves represents the spacing between adjacent etching positions, that is, the distance of the interval etching, that is, the etching spacing mentioned in the present invention.

[0070] In one embodiment, the distance between the annular groove closest to the bottom surface of the hierarchical microstructure and the bottom surface of the hierarchical microstructure is 5 μm-50 μm. It can be understood that from the bottom surface of the hierarchical microstructure to the direction away from the bottom surface of the flexible conductive substrate, the distance between the first annular groove and the bottom surface of the hierarchical microstructure is 5 μm-50 μm. This arrangement can ensure that the hierarchical microstructure has compressibility while ensuring its structural stability.

[0071] In one embodiment, during the second laser etching process, the etching path is parallel to the bottom surface of the first microstructure. This arrangement facilitates improving the stability of the hierarchical microstructure, thereby improving the sensitivity and detection range of the sensor, and maintaining the linearity of the output signal within the entire measurement range.

[0072] Taking into account the size of the hierarchical microstructure (such as height, bottom side length, etc.), the performance of the sensor can be regulated. Preferably, in the present invention, the height of the first microstructure is 10μm-500μm, and when the bottom surface of the first microstructure is square, the bottom side length of the first microstructure is 20μm-1000μm. When the bottom surface of the first microstructure is circular, the diameter of the first microstructure is 20μm-1000μm. This arrangement facilitates the regulation of the sensitivity and detection range of the sensor.

[0073] In one embodiment, in step S2, the material of the second flexible substrate is selected from at least one of polydimethylsiloxane, thermoplastic polyurethane elastomer, and polytrimethylene carbonate. Since polydimethylsiloxane has the best biocompatibility and thermal stability, polydimethylsiloxane is preferably used in the present invention.

[0074] In one embodiment, the second flexible substrate has a thickness of 50 μm-200 μm.

[0075] Furthermore, in step S2, the electrode provided on one surface of the second flexible substrate is preferably an interdigitated electrode, which can be prepared by referring to the following method: treating the second flexible substrate with oxygen plasma, and then preparing it by surface printing or 3D printing, and curing it at 25°C-150°C to obtain the interdigitated electrode.

[0076] It should be noted that the electrode is in contact with the hierarchical microstructure, that is, in the initial state, the electrode only contacts the surface of the first layer located at the highest point of the hierarchical microstructure, and as the pressure increases, the contact area between the first layer and the electrode increases.

[0077] At the same time, it should be noted here that in the present invention, a flexible conductive substrate with a hierarchical microstructure on the surface is directly used as the first substrate, so that it has both conductive and flexible effects. At the same time, the second flexible substrate in the second substrate is also flexible. Therefore, under sufficient pressure, electrical contact can be achieved between the hierarchical pyramid microstructure and the electrode.

[0078] Therefore, in the preparation method of the present invention, laser etching is directly used to etch the hierarchical microstructure on the surface of the flexible conductive substrate, which has a simple process, low cost, environmental protection and no pollution, and can be mass-produced industrially. At the same time, the side wall of the obtained hierarchical microstructure has at least one annular groove, so that the hierarchical microstructure has at least 2 levels, especially when the number of annular grooves is at least two, as the number of annular grooves increases, the number of levels of the hierarchical microstructure is higher, and the degree of deformability of the hierarchical microstructure is higher, so that the flexible pressure sensor can improve the detection range and reliability while improving the sensitivity. At the same time, due to the presence of annular grooves, especially when the number of annular grooves is at least two, the hierarchical microstructure is similar to a spring structure, thereby increasing the compressibility of the hierarchical microstructure, avoiding the problem that the compressibility of the hierarchical microstructure decreases with the increase of pressure, and thus making the output signal in the entire pressure range have a good linear relationship.

[0079] Specifically, under the action of pressure, the first layer located at the highest point in the hierarchical microstructure deforms first, so that the contact area between the hierarchical microstructure and the electrode increases, the conductive path of the sensor increases, and the sensitivity is high. As the pressure increases, the second layer, the third layer and other layers with the next highest height will contact each other and contact the electrodes in turn, further increasing the conductive path of the sensor and maintaining the sensitivity of the sensor. At the same time, due to the presence of annular grooves between adjacent levels, the compressibility between adjacent levels is increased, thereby enhancing the compressibility of the hierarchical microstructure, avoiding the problem that the compressibility of the hierarchical microstructure decreases with the increase of pressure. Therefore, the hierarchical microstructure can increase the saturated contact area of ​​the sensor, increase the conductive path, and extend its pressure linear response range, thereby improving the sensitivity of the sensor while improving the detection range and reliability, and making the output signal in the entire pressure range present a good linear relationship, which is convenient for the later analysis and processing of the signal data in the sensor, and further improves the accuracy of the measurement data.

[0080] At the same time, the present invention also provides a flexible pressure sensor, comprising:

[0081] A first flexible substrate 5, comprising a flexible conductive substrate 1 and a hierarchical microstructure 3 provided on a surface of the flexible conductive substrate, wherein the flexible conductive substrate 1 and the hierarchical microstructure 3 are an integral structure, and a side wall of the hierarchical microstructure has at least one annular groove 4;

[0082] The second flexible substrate 6 includes a flexible substrate and an electrode disposed on a surface of the flexible substrate. The second flexible substrate 6 is stacked with the first flexible substrate 5, and the electrode is in contact with the hierarchical microstructure.

[0083] In this flexible pressure sensor, during the compression process of the hierarchical microstructure, the contact area between the hierarchical microstructure and the electrode increases, the conductive path of the sensor increases, and the sensitivity is high. When the pressure continues to increase, the contact area reaches saturation, and the slope of the general sensitivity curve gradually decreases. However, due to the setting of the annular groove on the side wall of the hierarchical microstructure, the compressibility of the hierarchical microstructure is improved, thereby playing a certain buffering role, so that the high sensitivity continues to be maintained, that is, before the contact area between the first layer and the electrode is saturated, it contacts the second layer, and so on. The multiple layers in the hierarchical microstructure contact each other and contact the electrode in turn, further increasing the conductive path of the sensor and maintaining the sensitivity of the sensor. Due to the presence of the annular groove between adjacent layers, the compressibility of the hierarchical microstructure is enhanced, avoiding the problem that the compressibility of the hierarchical microstructure decreases with the increase of pressure. Therefore, the hierarchical microstructure can increase the saturated contact area of ​​the sensor, increase the conductive path, and extend its pressure linear response range, thereby improving the detection range and reliability while improving the sensitivity of the sensor, and making the output signal present a good linear relationship within the entire pressure range.

[0084] Hereinafter, the flexible pressure sensor and the preparation method thereof will be further described through specific embodiments.

[0085] Example 1

[0086] Weigh 1g of polydimethylsiloxane (PDMS) prepolymer into a beaker, add 0.1g of carbon nanotubes and mix well, then weigh 0.1g of curing agent and add it into the beaker and stir well, place it under 0.1Torr vacuum conditions for 10min to remove bubbles, and obtain a mixed solution. Select a clean glass substrate, spin-coat the above mixed solution on its surface at a speed of 500rpm for 10s, and cure it at 60℃ to obtain a 150μm thick flexible conductive substrate.

[0087] Weigh 1g of polydimethylsiloxane (PDMS) prepolymer into a beaker, then weigh 0.1g of curing agent and add it to the beaker and stir evenly, place it under 0.1Torr vacuum conditions for 10 minutes to remove bubbles, and obtain a mixed solution. Select a clean glass substrate, spin-coat the above mixed solution on its surface at a speed of 500rpm for 10 seconds, and cure it at 60°C to obtain a second flexible substrate with a thickness of 150μm.

[0088] The flexible conductive substrate is placed on a plane processing platform with an adjustable angle. A pulsed laser with a wavelength of 355nm, a pulse width of 500fs, and a spot diameter of 20μm is used to etch grid lines on the surface of the flexible conductive substrate. The spacing between parallel lines is 100μm, the laser single pulse energy is 10μJ, and the scanning speed is 500mm / s. After etching, a tetrahedral microstructure array pattern is obtained, in which the bottom side length of the tetrahedral microstructure is 100μm and the height is 50μm. Then the processing plane is adjusted. The angle of the platform is adjusted, and at a surface position of the quadrangular pyramid microstructure 10 μm away from the bottom of the quadrangular pyramid microstructure, the PDMS / carbon nanotubes are etched away from bottom to top at equal intervals, the etching interval is 10 μm, and the etching path is parallel to the bottom surface of the quadrangular pyramid microstructure. Two etchings are performed in sequence, wherein the etching depth is 10 μm and the etching width is 5 μm. After completion, a hierarchical microstructure array pattern with two annular grooves on the surface is obtained, and the depth of the annular groove is 10 μm and the width is 5 μm, that is, a first flexible substrate is obtained.

[0089] The second flexible substrate was treated with oxygen plasma, and then the interdigitated electrodes were 3D printed on its surface and cured at 100°C. Two thin wires were cut and placed at the two ends of the interdigitated electrodes respectively, and then a layer of conductive silver glue was applied to fix the wires to obtain the second flexible substrate.

[0090] The second flexible substrate is stacked on the first flexible substrate so that the interdigital electrodes are in contact with the hierarchical microstructure, and the first flexible substrate and the second flexible substrate are packaged with 3M tape to obtain a flexible pressure sensor.

[0091] Example 2

[0092] Compared with Example 1, the only difference is that the flexible conductive substrate is placed on a plane processing platform with an adjustable angle, and a pulsed laser with a wavelength of 355nm, a pulse width of 500fs, and a spot diameter of 20μm is used to etch grid lines on the surface of the flexible conductive substrate, with a spacing of 500μm between parallel lines, a single laser pulse energy of 10μJ, and a scanning speed of 500mm / s. After the etching is completed, a quadrangular pyramid microstructure array pattern is obtained, wherein the bottom side length of the quadrangular pyramid microstructure is 500μm and the height is 100μm; then Then, the angle of the processing platform was adjusted, and the PDMS / carbon nanotubes were removed by etching from bottom to top at equal intervals at a position on the surface of the tetrahedral microstructure 10 μm away from the bottom of the tetrahedral microstructure. The etching interval was 10 μm, and the etching path was parallel to the bottom surface of the tetrahedral microstructure. Four etchings were performed in sequence, wherein the etching depth was 20 μm and the etching width was 5 μm. After completion, a hierarchical microstructure array pattern with four annular grooves on the surface was obtained, and each annular groove had a depth of 20 μm and a width of 5 μm, that is, a first flexible substrate was obtained.

[0093] Example 3

[0094] Compared with Example 1, the only difference is that in Example 3, the flexible conductive substrate is placed on a plane processing platform with an adjustable angle, and a pulsed laser with a wavelength of 355nm, a pulse width of 500fs, and a spot diameter of 20μm is used to etch grid lines on the surface of the flexible conductive substrate, with a spacing of 500μm between parallel lines, a single laser pulse energy of 10μJ, and a scanning speed of 500mm / s. After the etching is completed, a tetrahedral microstructure array pattern is obtained, wherein the bottom side length of the tetrahedral microstructure is 500μm and the height is 100μm; then the angle of the processing platform is adjusted to be at a distance from the tetrahedral The bottom of the microstructure is located on the surface of a tetrahedral microstructure of 10 μm. The PDMS / carbon nanotubes are removed by etching at equal intervals from bottom to top. The etching interval is 10 μm, and the etching path is parallel to the bottom of the tetrahedral microstructure. Etching is performed four times in sequence, and the etching depths are 20 μm, 15 μm, 10 μm, and 5 μm in sequence, and the etching width is 5 μm. After completion, a hierarchical microstructure array pattern with four annular grooves on the surface is obtained, and from bottom to top, the depths of the annular grooves are 20 μm, 15 μm, 10 μm, and 5 μm in sequence, and the widths of the four annular grooves are all 5 μm, that is, the first flexible substrate is obtained.

[0095] Example 4

[0096] Compared with Example 1, the only difference is that in Example 4, the flexible conductive substrate is placed on a plane processing platform with an adjustable angle, and a pulsed laser with a wavelength of 355nm, a pulse width of 500fs, and a spot diameter of 20μm is used to etch grid lines on the surface of the flexible conductive substrate, with a spacing of 800μm between parallel lines, a laser single pulse energy of 10μJ, and a scanning speed of 500mm / s. After the etching is completed, a tetrahedral microstructure array pattern is obtained, wherein the bottom side length of the tetrahedral microstructure is 800μm and the height is 200μm; then the angle of the processing platform is adjusted, and the PD is removed from the surface of the tetrahedral microstructure 15μm away from the bottom of the tetrahedral microstructure by etching at equal intervals from bottom to top. MS / carbon nanotube, the etching spacing is 10μm, the etching path is parallel to the bottom surface of the tetrahedral microstructure, and etching is performed 6 times in sequence, and the etching depths are 100μm, 80μm, 60μm, 40μm, 20μm, and 5μm in sequence, and the etching widths are 20μm, 30μm, 30μm, 20μm, 15μm, and 10μm respectively; after completion, a hierarchical microstructure array pattern with 6 annular grooves on the surface is obtained, and from bottom to top, the depths of the annular grooves are 100μm, 80μm, 60μm, 40μm, 20μm, and 5μm, and the widths of the annular grooves are 20μm, 30μm, 30μm, 20μm, 15μm, and 10μm, respectively, that is, the first flexible substrate is obtained.

[0097] The differences between Example 5 to Example 10 and Example 1 are shown in Table 1.

[0098] Table 1

[0099]

[0100] Comparative Example 1

[0101] Compared with Example 3, the only difference is that in Comparative Example 1, the obtained quadrangular pyramid microstructure array pattern is no longer etched, and the Figure 2 The flexible conductive substrate having a quadrangular pyramid microstructure on its surface is shown as the first flexible substrate.

[0102] Comparative Example 2

[0103] Compared with Example 3, the only difference is that in Comparative Example 2, the flexible conductive substrate is placed on a flat processing table, and a pulsed laser with a wavelength of 355nm, a pulse width of 500fs, and a spot diameter of 20μm is used to etch grid lines on the surface of the flexible conductive substrate. The spacing between parallel lines is 500μm, the laser single pulse energy is 10μJ, and the scanning speed is 500mm / s. After etching, a tetrahedral microstructure array with three heights is obtained, wherein the bottom side length of the tetrahedral microstructure is 500μm, and the heights are 100μm, 70μm, and 40μm, respectively. Directly as shown in Figure 5 The flexible conductive substrate shown has a surface with an array of quadrangular pyramid microstructures of three heights as the first flexible substrate.

[0104] The differences between Comparative Examples 3 to 9 and Example 1 are shown in Table 2.

[0105] Table 1

[0106]

[0107] The relationship between the current change rate and pressure of the sensors of Example 3 of the present invention and Comparative Examples 1 and 2 was tested. The results are as follows: Figure 6-8 As shown. Figure 6-8 It can be seen that the linear detection range of the sensor of Example 3 of the present invention is 0kPa-500kPa, and the sensitivity is about 4.5kPa -1 The sensitivity of the sensor in comparative example 1 is about 3.7 kPa. -1 , the pressure range is 0kPa-40kPa, which is obviously weaker than the sensor of the present invention, and there is no linear detection range.

[0108] In addition, the range detection range of the sensor in comparative example 2 is roughly divided into two sections, namely, a linear detection range and a curve detection range. Specifically, it is linearly detected in the range of 0kPa-45kPa, and the sensitivity is about 5.8kPa. -1As the pressure increases, that is, within the range of 45kPa-150kPa, it presents an obvious curve with a sensitivity of 0.87kPa -1 . This is because as the pressure increases, the compressibility of the microstructure gradually decreases. At the same time, when the sensor of comparative document 2 is used to detect pressure, not only does it make the subsequent signal processing circuit complicated, it requires complex analysis and calculation, which brings great inconvenience to the calibration and data processing of the pressure sensor, but also due to the appearance of the segmented curve, it is difficult to calibrate the pressure in the interval, thereby affecting the accuracy of the measurement during the period. The sensor of embodiment 3 of the present invention maintains a linear output signal within the entire pressure range.

[0109] It can be seen that the flexible pressure sensor of the present invention can not only improve sensitivity while having a wide detection range and reliability, but also make the output signal present a good linear relationship in the entire pressure range, thereby facilitating the subsequent analysis and processing of signal data in the sensor, and further improving the accuracy of the measurement data.

[0110] At the same time, this flexible pressure sensor can be used as a wearable electronic product, and has great application prospects in intelligent robots and human physiological signal monitoring. For example, in human physiological signal monitoring, the flexible pressure sensor can be attached to the surface of the human chest to monitor heart rate, to the wrist to detect arterial pulsation, and to the throat to detect vocal cord vibration.

[0111] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0112] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a flexible pressure sensor, It is characterized in that include: Providing a flexible conductive substrate, using a first laser to etch a surface of the flexible conductive substrate to form a plurality of first microstructures of the same height, and then using a second laser to etch the sidewalls of the first microstructures to form a hierarchical microstructure having at least one annular groove, thereby obtaining a first flexible substrate; Providing a second flexible substrate, wherein the second flexible substrate comprises a second flexible substrate and an electrode disposed on a surface of the second flexible substrate; The second flexible substrate is stacked on the first flexible substrate, and the electrode is in contact with the hierarchical microstructure to obtain a flexible pressure sensor.

2. The method for preparing the flexible pressure sensor according to claim 1, It is characterized in that Along the direction in which the first microstructure moves away from the flexible conductive substrate, the cross-sectional width of the first microstructure gradually decreases.

3. The method for preparing the flexible pressure sensor according to claim 1 or 2, It is characterized in that When the number of the annular grooves is at least two, with the direction from the groove mouth to the groove bottom of the annular groove as the depth direction, the depth of adjacent annular grooves tends to gradually decrease or gradually increase from the side of the hierarchical microstructure close to the flexible conductive substrate to the side away from the flexible conductive substrate.

4. The method for preparing the flexible pressure sensor according to claim 1 or 2, It is characterized in that When the number of the annular grooves is at least two, the direction from the groove opening to the groove bottom of the annular groove is the depth direction, and the depths of adjacent annular grooves are the same.

5. The method for preparing the flexible pressure sensor according to claim 3, It is characterized in that The depth of the annular groove is 10 μm-500 μm, and the width of the annular groove is 5 μm-200 μm.

6. The method for preparing the flexible pressure sensor according to claim 1, It is characterized in that When the number of the annular grooves is at least two, during the second laser etching process, the annular grooves are sequentially and spaced apart from each other on the sidewalls of the first microstructure from the bottom surface of the first microstructure toward a direction away from the bottom surface of the flexible conductive substrate.

7. The method for preparing the flexible pressure sensor according to claim 1, It is characterized in that When the number of the annular grooves is at least two, the distances between adjacent annular grooves are the same; And / or, when the number of the annular grooves is at least two, the distance between adjacent annular grooves is 5 μm-50 μm; And / or, the distance between the annular groove closest to the bottom surface of the hierarchical microstructure and the bottom surface of the hierarchical microstructure is 5 μm-50 μm.

8. The method for preparing the flexible pressure sensor according to claim 1, It is characterized in that During the second laser etching process, the etching path is parallel to the bottom surface of the first microstructure.

9. The method for preparing the flexible pressure sensor according to claim 1, It is characterized in that The height of the first microstructure is 10 μm-500 μm; And / or, when the bottom surface of the first microstructure is a square, the side length of the bottom surface of the first microstructure is 20 μm-1000 μm.

10. A flexible pressure sensor, It is characterized in that include: A first flexible substrate, comprising a flexible conductive substrate and a plurality of hierarchical microstructures disposed on a surface of the flexible conductive substrate, wherein the flexible conductive substrate and the hierarchical microstructures are an integral structure, and a side wall of the hierarchical microstructure has at least one annular groove; The second flexible substrate comprises a flexible substrate and an electrode disposed on a surface of the flexible substrate. The second flexible substrate is stacked with the first flexible substrate, and the electrode is in contact with the hierarchical microstructure.

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