A flexible sensor device based on silicon nanowire array and its preparation method

Abstract

The present invention relates to a flexible sensor device based on a silicon nanowire array and a preparation method thereof, belonging to the field of sensor technology. The preparation method of the present invention comprises the following steps: S1, after silver plating the surface of a silicon wafer, etching is performed once to form a silicon nanowire array; S2, ultrasonic induction and secondary etching are performed on the silicon wafer after the primary etching to form cracks at the bottom of the silicon nanowire array; S3, a tackifier is applied to the top of the silicon nanowire array, and then the silicon nanowire array is transferred to the substrate surface under heating conditions, and peeled, cured, and ultrasonically induced twice; S4, a second electrode is set on the top of the silicon nanowire array after the secondary ultrasonic induction to obtain the flexible sensor device based on the silicon nanowire array. The preparation method of the present invention constructs a flower-like silicon nanowire array that is gathered at the bottom and open and neat at the top, which can evaporate, rub, adsorb, and desorb tiny water droplets faster to obtain a faster response and a better signal-to-noise ratio.

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] Respiratory disorders have always been a concern for countries around the world. In addition, breathing patterns and quality of breathing have a very important impact on the health monitoring and quality of life management of the elderly. A respiratory sensing system for respiratory disorders can better solve such problems. Traditional sensing systems achieve the purpose of sensing by sensing muscle electrical signals caused by changes in human muscle or vocal cord vibration. They have defects such as complex equipment manufacturing, difficult signal acquisition, and poor wearability. In order to ensure signal sensitivity and signal-to-noise ratio, existing hydrovoltaic moisture adsorption power generation devices mostly use inorganic silicon, silicon carbide and other materials. However, these materials have poor flexibility and toughness, making it 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, sensing elements are typically patterned onto flexible substrates to achieve flexibility, offering a new approach to building flexible sensor devices. However, the three-dimensional structure of the functional layers of silicon-based sensor devices places high demands on their transfer. Therefore, transferring the entire silicon nanowire sensor array onto a flexible substrate while preserving its integrity has become a challenge. 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 with aggregation at the bottom and looseness 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 silicon wafer surface, 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. Setting 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 primary etching and the secondary etching are both obtained by dissolving hydrogen fluoride and hydrogen peroxide in water; the concentration of hydrogen fluoride in the etching solution is 4.5 mol / L-5 mol / L, and the concentration of hydrogen peroxide is 0.02 mol / L-0.05 mol / 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 this temperature condition, 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 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 a silicon nanowire array 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 a 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 at the top, which can evaporate, rub, adsorb, and desorb tiny water droplets faster, thereby obtaining a faster response and a 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 This is a characterization 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 in Example 1 of the present invention;

[0032] Figure 7 Response results of the sensor device of Comparative Example 1 of the present invention;

[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 will be further described below with reference to specific embodiments so that those skilled in the art can better understand and implement the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. It should be understood that the specific embodiments are only used to illustrate the present invention, and the embodiments are not intended to limit the present invention.

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

[0036] In the present invention, unless stated otherwise, 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 examples 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 laser marking and perform RCA standard cleaning, acetone cleaning, concentrated sulfuric acid cleaning, and oxygen plasma cleaning to obtain a clean silicon wafer;

[0043] S2. Use anti-corrosion silicone adhesive to encapsulate the back of the silicon wafer (i.e., apply tape to the back side that is not etched) to protect it, heat and cure the back side, and then place the encapsulated silicon wafer on a plastic rack;

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

[0045] S4. After the first etching, the silicon wafer is cleaned in deionized water and then dried. After drying, the silicon wafer is vertically adhered to a plastic rack, placed in 60°C water, and ultrasonically treated at a frequency of 45,000 Hz for 3 minutes to induce rearrangement of the silver nanoparticles.

[0046] S5. Place the ultrasonically treated silicon wafer in an etching solution for a second etching to form a bottom crack, then place the wafer in nitric acid to wash away the remaining silver, rinse with clean water, and then dry. The second etching temperature 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 on the dried silicon wafer; construct a PET substrate with a thickness of approximately 100 μm and a 10 μm copper electrode using 3D printing; heat the copper electrode and PET substrate to 150°C in a semi-molten state, transfer the silicon nanowire array to the substrate surface (the side coated with HMDS is attached to the copper electrode), 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.

[0048] S7. Place the cooled material in 60°C water and ultrasonically treat it at a frequency of 45,000 Hz for 3 minutes to induce fracture, thereby achieving a more uniform and higher-yield silicon nanowire functional layer transfer;

[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 laser marking and perform RCA standard cleaning, acetone cleaning, concentrated sulfuric acid cleaning, and oxygen plasma cleaning to obtain a clean silicon wafer;

[0053] S2. Use anti-corrosion silicone adhesive to encapsulate the back of the silicon wafer (i.e., apply tape to the back side that is not etched) to protect it, heat and cure the back side, and then place the encapsulated silicon wafer on a plastic rack;

[0054] S3. Silver is plated on the surface of the silicon wafer using a thermal evaporation method, and the wafer is immersed in an etching solution for the first etching while stirring at a low speed to ensure uniform etching, forming silicon nanowires with a length of about 30 μm. The remaining silver is then washed away in nitric acid, and the wafer is dried after rinsing with clean water. 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. The method specifically includes the following steps:

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

[0058] S2. Use anti-corrosion silicone adhesive to encapsulate the back of the silicon wafer (i.e., apply tape to the back side that is not etched) to protect it, heat and cure the back side, and then place the encapsulated silicon wafer on a plastic rack;

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

[0060] S4. After the first etching, the silicon wafer is cleaned in deionized water and then dried. After drying, the silicon wafer is vertically adhered to a plastic rack, placed in 60°C water, and ultrasonically treated at a frequency of 45,000 Hz for 3 minutes to induce rearrangement of the silver nanoparticles.

[0061] S5. Place the ultrasonically treated silicon wafer in an etching solution for a second etching to form a bottom crack, then place the wafer in nitric acid to wash away the remaining silver, rinse with clean water, and then dry. The second etching temperature 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 approximately 100 μm and a copper electrode with a thickness of 10 μm. Heat the copper electrode and PET substrate to 150°C in a semi-molten state, transfer the silicon nanowire array to the substrate surface, 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 were 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 and uneven distribution of pores; Figure 4 It can be seen that the silicon nanowires on the top of the sensor device of Comparative Example 2 are relatively disordered.

[0066] Test Example 2

[0067] The sensor device of Example 1 is cut into a rectangle of 1cm*6cm, referring to Figure 5 To perform a bending performance test, clamp both ends onto a horizontal translation stage and tighten the stage by turning the knob to prevent the device from loosening during the test. Fix the scale in front of the stage and then turn the knob on the side of the 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 and an exhalation test was performed. The exhalation intensity was controlled to be roughly the same, and a "ha" sound was emitted 5 times in a row. The data of the obtained current intensity change over time was collected and plotted. The results are shown in Figure 1. 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 of 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 the silicon nanowires on the top of the sensor device have a large number of clusters and uneven distribution of pores, resulting in insufficient friction. Figure 8 It can be seen that the sensor device of Comparative Example 2 has weak signal strength and low signal-to-noise ratio. This is because the silicon nanowires on the top of the sensor device are relatively messy.

[0070] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present 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 silicon wafer surface, 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 curing, secondary ultrasonic induction, and peeling; 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 top of the silicon nanowire array after secondary ultrasound induction to obtain the flexible sensor device based on the silicon nanowire array; The first ultrasonic induction and the second ultrasonic induction are both performed 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.

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

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

5. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, wherein: 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, wherein: In S3, the heating condition is a temperature of 140°C to 210°C.

7. The method for preparing a flexible sensor device based on a silicon nanowire array according to claim 1, wherein: 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, wherein: 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.

9. A flexible sensor device based on a silicon nanowire array prepared by the method according to any one of claims 1 to 8.

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