Flexible sensing device based on silicon nanowire array and preparation method thereof

Abstract

The invention relates to a flexible sensing device based on a silicon nanowire array and a preparation method of the flexible sensing device, and belongs to the technical field of sensors. The preparation method comprises the following steps: S1, plating silver on the surface of a silicon wafer, and performing primary etching to form a silicon nanowire array; s2, performing primary ultrasonic induction and secondary etching on the silicon wafer after primary etching, and forming cracks at the bottom of the silicon nanowire array; s3, coating the top of the silicon nanowire array with a tackifier, then transferring the silicon nanowire array to the surface of the substrate under a heating condition, and performing stripping, curing and secondary ultrasonic induction; and S4, arranging a second electrode on the top of the silicon nanowire array after the secondary ultrasonic induction to obtain the flexible sensing device based on the silicon nanowire array. According to the preparation method disclosed by the invention, the flowering-shaped silicon nanowire array of which the bottom is gathered and the top is opened and tidy is constructed, and evaporation, friction, adsorption and desorption of tiny water drops can be carried out more quickly, so that faster response and better signal-to-noise ratio are obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and in particular relates to a flexible sensor device based on a silicon nanowire array and a preparation method thereof. Background Art

[0002] The problem of respiratory disorders has always been one of the issues that have attracted attention from all over the world. In addition, breathing patterns and breathing quality have a very important impact on the life health monitoring and quality of life management of the elderly. The respiratory sensing system for respiratory disorders can better solve such problems. The traditional sensing system achieves the purpose of sensing by sensing the muscle electrical signals caused by changes in the vibration of human muscles or vocal cords. It has defects such as complex equipment manufacturing, difficult signal acquisition, and poor wearability. In order to ensure the sensitivity and signal-to-noise ratio of the signal, the existing hydrovoltaic moisture adsorption power generation devices mostly use inorganic silicon, silicon carbide and other materials. However, this type of material has poor flexibility and toughness, and it is difficult to cope with complex physical scenarios. Therefore, improving the flexibility of silicon-based sensor devices has become an important issue.

[0003] In the existing field of flexible sensors, the sensing unit is generally engraved on a flexible substrate to achieve flexibility, which provides a new idea for the construction of flexible sensor devices. However, the three-dimensional structure of the functional layer of the silicon-based sensor device has high requirements for the transfer of the functional layer. Therefore, it has become a problem to transfer the complete flexible substrate while keeping the silicon nanowire sensor array unchanged. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a flexible sensor device based on a silicon nanowire array and a preparation method thereof. The functional structure of the silicon nanowires of the flexible sensor device is a flower-like silicon nanowire structure that is aggregated at the bottom and loose at the top, which is conducive to the friction, adsorption, desorption of moisture and the generation of electrical signals, thereby realizing the efficient and complete transfer of the silicon nanowire array and constructing a high-performance flexible sensor device.

[0005] The first object of the present invention is to provide a method for preparing a flexible sensor device based on a silicon nanowire array, comprising the following steps:

[0006] S1, after silver plating on the surface of the silicon wafer, etching is performed once to form a silicon nanowire array;

[0007] S2, performing an ultrasonic induction and a secondary etching on the silicon wafer after the primary etching to form a crack at the bottom of the silicon nanowire array;

[0008] S3, applying a tackifier on the top of the silicon nanowire array, then transferring the silicon nanowire array to the surface of a substrate under heating conditions, and performing peeling, curing, and secondary ultrasonic induction; the substrate includes a polymer substrate and a first electrode disposed on the surface of the polymer substrate; the first electrode is disposed between the silicon nanowire array and the polymer substrate;

[0009] S4. Disposing a second electrode on the top of the silicon nanowire array after secondary ultrasonic induction to obtain the flexible sensor device based on the silicon nanowire array.

[0010] In one embodiment of the present invention, in S1, the length of the silicon nanowire is 20 μm-30 μm;

[0011] The temperature of the first etching is 30° C.-50° C., and the time is 25 min-35 min.

[0012] In one embodiment of the present invention, in S2, the temperature of the secondary etching is 30° C.-50° C., and the time is 3 min-8 min.

[0013] In one embodiment of the present invention, in S1 and S2, the etching solutions used in the first etching and the second etching are both obtained by dissolving hydrogen fluoride and hydrogen peroxide in water; the concentration of hydrogen fluoride in the etching solution is 4.5mol / L-5mol / L, and the concentration of hydrogen peroxide is 0.02mol / L-0.05mol / L.

[0014] In one embodiment of the present invention, in S3, the adhesion promoter is hexamethyldisilazane (HMDS) to enhance its viscosity so as to facilitate its more stable adhesion to the substrate surface.

[0015] In one embodiment of the present invention, in S3, the peeling method is selected from mechanical peeling or ultrasonic vibration peeling.

[0016] In one embodiment of the present invention, in S3, the heating condition is at a temperature of 140°C-210°C, under which the polymer substrate is in a semi-molten state, which is conducive to slightly inserting the silicon nanowire array into the polymer substrate by its own weight and tightly adhering to the inside of the polymer substrate.

[0017] In one embodiment of the present invention, in S3, the polymer substrate is selected from polyethylene terephthalate (PET) or thermoplastic polyurethane elastomer; the thickness of the polymer substrate is 80 μm-120 μm, has certain adhesion and biocompatibility, and can be applied to the surface of human skin for sensing applications.

[0018] In one embodiment of the present invention, in S2 and S3, the first ultrasonic induction and the second ultrasonic induction are both performed by ultrasonic treatment in a water bath; the temperature of the water bath is 55°C-65°C, and the ultrasonic treatment is performed at a frequency of 42000Hz-48000Hz for 2min-4min.

[0019] In one embodiment of the present invention, in S3 and S4, the materials of the first electrode and the second electrode are independently selected from silver and / or copper, and the thicknesses are independently 5 μm-15 μm.

[0020] The second object of the present invention is to provide a flexible sensor device based on silicon nanowire arrays prepared by the method described above.

[0021] The technical solution of the present invention has the following advantages over the prior art:

[0022] (1) The preparation method described in the present invention transfers the silicon nanowire array from the hard silicon substrate during etching growth to the polymer substrate, so that the sensor device can be bent to cope with a variety of complex mechanical environments and application scenarios.

[0023] (2) The preparation method described in the present invention constructs a flower-like silicon nanowire array that is aggregated at the bottom and open and neat at the top, which can evaporate, rub, adsorb, and desorb tiny water droplets faster to obtain faster response and better signal-to-noise ratio.

[0024] (3) The preparation method described in the present invention can realize the preparation of large-scale silicon nanowire arrays. The polymer substrate used has ultra-high flexibility and can be directly cut into various shapes using scissors, lasers, hand tearing, etc. as needed, and is suitable for a variety of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 This is a process flow chart of a flexible sensor device based on a silicon nanowire array in Example 1 of the present invention;

[0027] Figure 2 is a representation diagram of the sensor device according to Example 1 of the present invention;

[0028] Figure 3 This is a characterization diagram of the sensor device of Comparative Example 1 of the present invention;

[0029] Figure 4 This is a characterization diagram of the sensor device of Comparative Example 2 of the present invention;

[0030] Figure 5This is the bending performance test of Test Example 2 of the present invention;

[0031] Figure 6 is the response result of the sensor device of Example 1 of the present invention;

[0032] Figure 7 The response result of the sensor device of comparative example 1 of the present invention is shown in FIG.

[0033] Figure 8 This is the response result of the sensor device of comparative example 2 of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0035] In the present invention, unless otherwise defined, technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs.

[0036] In the present invention, unless otherwise stated, the term "and / or" used in the present invention includes any and all combinations of one or more of the associated listed items.

[0037] In the present invention, unless otherwise stated, the experimental methods used in the embodiments of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0038] In the present invention, unless otherwise specified, the silicon wafer used in the embodiments of the present invention is an N-type highly doped silicon wafer.

[0039] In the present invention, unless otherwise specified, the etching solution used in the embodiments of the present invention is prepared by dissolving hydrogen fluoride and hydrogen peroxide in water; the concentration of hydrogen fluoride in the etching solution is 4.8 mol / L, and the concentration of hydrogen peroxide is 0.03 mol / L.

[0040] Example 1

[0041] Reference Figure 1 As shown, the flexible sensor device based on silicon nanowire array and the preparation method thereof of the present invention specifically include the following steps:

[0042] S1. Cut a 500 μm thick silicon wafer into 6*6 cm squares using a laser marking method and perform RCA standard cleaning, acetone cleaning, concentrated sulfuric acid cleaning, and oxygen plasma cleaning to obtain a clean silicon wafer;

[0043] S2, using anti-corrosion silicone glue to encapsulate the back of the silicon wafer (i.e., sticking tape on the back side that is not etched) to protect it, heating and curing the back side, and then placing the encapsulated silicon wafer on a plastic frame;

[0044] S3, using a thermal evaporation method to plate silver on the surface of the silicon wafer, and immersing it in an etching solution for the first etching, while stirring at a low speed to ensure uniform etching, to form silicon nanowires with a length of about 30 μm; wherein the temperature of the first etching is about 40° C., and the time is about 30 minutes;

[0045] S4, washing the silicon wafer after the first etching in deionized water and drying it, adhering the silicon wafer vertically to a plastic frame after drying, placing it in 60°C water, and ultrasonically treating it at a frequency of 45000 Hz for 3 minutes to induce rearrangement of the silver nanoparticles;

[0046] S5, placing the ultrasonically treated silicon wafer in an etching solution for a second etching to form a bottom crack, placing it in nitric acid to wash away the residual silver, rinsing it with clean water and drying it; wherein the temperature of the second etching is about 40° C., and the time is about 5 minutes;

[0047] S6. Apply a layer of hexamethyldisilazane HMDS on the top of the nanowire array of the dried silicon wafer; construct a PET substrate with a thickness of about 100 μm and a copper electrode with a thickness of 10 μm by 3D printing; heat the copper electrode and the PET substrate to 150°C in a semi-molten state, transfer the silicon nanowire array to the substrate surface (the side coated with HMDS fits the copper electrode), use the silicon nanowire array's own weight to slightly insert and tightly adhere to the inside of the polymer substrate, then perform ultrasonic peeling and cool to room temperature to obtain a more stable silicon nanowire functional layer-electrode layer-flexible substrate layer;

[0048] S7, placing the cooled material in 60°C water, and ultrasonically treating it at a frequency of 45000 Hz for 3 minutes to induce fracture, thereby achieving a more orderly transfer of the silicon nanowire functional layer with a higher yield;

[0049] S8. A copper electrode with a thickness of 10 μm is arranged on the top of the silicon nanowire array after ultrasonic treatment to obtain a flexible sensor device based on the silicon nanowire array.

[0050] Comparative Example 1

[0051] The method is basically the same as Example 1, except that subsequent steps such as secondary etching are not performed. Specifically, the method includes the following steps:

[0052] S1. Cut a 500 μm thick silicon wafer into 6 cm*6 cm squares using a laser marking method and perform RCA standard cleaning, acetone cleaning, concentrated sulfuric acid cleaning, and oxygen plasma cleaning to obtain a clean silicon wafer;

[0053] S2, using anti-corrosion silicone glue to encapsulate the back of the silicon wafer (i.e., sticking tape on the back side that is not etched) to protect it, heating and curing the back side, and then placing the encapsulated silicon wafer on a plastic frame;

[0054] S3. Silver is plated on the surface of the silicon wafer by thermal evaporation, and the wafer is immersed in an etching solution for the first etching, while stirring at a low speed to ensure uniform etching, to form silicon nanowires with a length of about 30 μm, and then placed in nitric acid to wash away the residual silver, rinsed with clean water and dried; wherein, the temperature of the first etching is about 40°C, and the time is about 30 minutes.

[0055] Comparative Example 2

[0056] The method is basically the same as Example 1, except that no induced fracture is performed after HMDS treatment and cooling, and specifically comprises the following steps:

[0057] S1. Cut a 500 μm thick silicon wafer into 6*6 cm squares using a laser marking method and perform RCA standard cleaning, acetone cleaning, concentrated sulfuric acid cleaning, and oxygen plasma cleaning to obtain a clean silicon wafer;

[0058] S2, using anti-corrosion silicone glue to encapsulate the back of the silicon wafer (i.e., sticking tape on the back side that is not etched) to protect it, heating and curing the back side, and then placing the encapsulated silicon wafer on a plastic frame;

[0059] S3, using a thermal evaporation method to plate silver on the surface of the silicon wafer, and immersing it in an etching solution for the first etching, while stirring at a low speed to ensure uniform etching, to form silicon nanowires with a length of about 30 μm; wherein the temperature of the first etching is about 40° C., and the time is about 30 minutes;

[0060] S4, washing the silicon wafer after the first etching in deionized water and drying it, adhering the silicon wafer vertically to a plastic frame after drying, placing it in 60°C water, and ultrasonically treating it at a frequency of 45000 Hz for 3 minutes to induce rearrangement of the silver nanoparticles;

[0061] S5, placing the ultrasonically treated silicon wafer in an etching solution for a second etching to form a bottom crack, placing it in nitric acid to wash away the residual silver, rinsing it with clean water and drying it; wherein the temperature of the second etching is about 40° C., and the time is about 5 minutes;

[0062] S6. Use 3D printing to construct a PET substrate with a thickness of about 100 μm and a copper electrode with a thickness of 10 μm. Heat the copper electrode and the PET substrate to 150°C in a semi-molten state, transfer the silicon nanowire array to the surface of the substrate, and use the silicon nanowire array's own weight to slightly insert and tightly adhere to the inside of the polymer substrate. Then, perform ultrasonic peeling and cool to room temperature to obtain a more stable silicon nanowire functional layer-electrode layer-flexible substrate layer.

[0063] S7. A copper electrode with a thickness of 10 μm is arranged on the top of the silicon nanowire array of the cooled material to obtain a sensor device.

[0064] Test Example 1

[0065] The sensor devices prepared in Example 1 and Comparative Examples 1-2 were characterized, and the results are as follows: Figure 2-Figure 4 As shown. Figure 2 It can be seen that the silicon nanowires on the top of the sensor device of Example 1 are evenly distributed; Figure 3 It can be seen that the silicon nanowires on the top of the sensor device of Comparative Example 1 have a large number of clusters of pores that are unevenly distributed; Figure 4 It can be seen that the silicon nanowires on the top of the sensor device of Comparative Example 2 are relatively messy.

[0066] Test Example 2

[0067] The sensor device of Example 1 is cut into a rectangle of 1 cm*6 cm, referring to Figure 5 To perform the bending performance test, clamp the two ends onto the horizontal translation stage and turn the knob to tighten the translation stage to prevent the device from loosening during the test. Fix the scale in front of the translation stage and turn the knob on the side of the translation stage to compress it. Figure 5 It can be observed that the curvature radius of the sensor device is between 1cm and 1.5cm, and its bending performance far exceeds that of hard silicon devices.

[0068] Test Example 3

[0069] The electrode connection wires of the sensor devices prepared in Example 1 and Comparative Examples 1-2 were connected to the current signal test instrument Keithly to perform an exhalation test. The exhalation intensity was controlled to be roughly the same, and a "Ha" sound was emitted for 5 consecutive times. The data of the obtained current intensity changing with time were collected and plotted. The results are shown in Figure 6-Figure 8 As shown. Figure 6 It can be seen that the electrical signal of the sensor device of Example 1 is highly recognizable and can quickly form 5 distinguishable signals. This is because the silicon nanowires on the top of the sensor device are evenly distributed. Figure 7It can be seen that the signal of the sensor device in Comparative Example 1 is weak, and due to problems such as incomplete evaporation, there are large noises and abnormal signals, making it difficult to form five continuous and distinguishable signals. This is because there are a large number of clusters of silicon nanowires on the top of the sensor device, which are unevenly distributed, resulting in insufficient friction. Figure 8 It can be seen that the signal strength and signal-to-noise ratio of the sensor device of Comparative Example 2 are weak because the silicon nanowires on the top of the sensor device are relatively messy.

[0070] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing a flexible sensor device based on a silicon nanowire array, characterized in that: The following steps are involved: S1, after silver plating on the surface of the silicon wafer, etching is performed once to form a silicon nanowire array; S2, performing an ultrasonic induction and a secondary etching on the silicon wafer after the primary etching to form a crack at the bottom of the silicon nanowire array; S3, applying a tackifier on the top of the silicon nanowire array, then transferring the silicon nanowire array to the surface of a substrate under heating conditions, and performing peeling, curing, and secondary ultrasonic induction; the substrate includes a polymer substrate and a first electrode disposed on the surface of the polymer substrate; the first electrode is disposed between the silicon nanowire array and the polymer substrate; S4. Disposing a second electrode on the top of the silicon nanowire array after secondary ultrasonic induction to obtain the flexible sensor device based on the silicon nanowire array.

2. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S1, the length of the silicon nanowire is 20 μm-30 μm; The temperature of the first etching is 30° C.-50° C., and the time is 25 min-35 min.

3. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S2, the temperature of the secondary etching is 30°C-50°C, and the time is 3min-8min.

4. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S1 and S2, the etching solutions used in the first etching and the second etching are both obtained by dissolving hydrogen fluoride and hydrogen peroxide in water; the concentration of hydrogen fluoride in the etching solution is 4.5mol / L-5mol / L, and the concentration of hydrogen peroxide is 0.02mol / L-0.05mol / L.

5. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S3, the adhesion promoter is hexamethyldisilazane.

6. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S3, the heating condition has a temperature of 140°C-210°C.

7. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S3, the polymer substrate is selected from polyethylene terephthalate or thermoplastic polyurethane elastomer; and the thickness of the polymer substrate is 80 μm-120 μm.

8. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S2 and S3, the first ultrasonic induction and the second ultrasonic induction are both performed by ultrasonic treatment in a water bath; the temperature of the water bath is 55° C.-65° C., and the ultrasonic treatment is performed at a frequency of 42000 Hz-48000 Hz for 2 min-4 min.

9. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, characterized in that: In S3 and S4, the materials of the first electrode and the second electrode are independently selected from silver and / or copper, and the thicknesses are independently 5 μm-15 μm.

10. A flexible sensor device based on silicon nanowire arrays prepared by the method according to any one of claims 1 to 9.

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