Design and manufacturing of flexible proximity sensor

Abstract

The invention discloses a liquid metal-based flexible proximity sensor formed through a mask spraying process. According to the manufacturing process, the manufacturing process and the performance of the proximity sensor are remarkably optimized. Through the improvement of the structural design, the thickness of the sensor is successfully reduced to be within 1mm, and the flexibility and adhesive force of the sensor in large-scale production and complex surface application are greatly improved. And secondly, in the aspect of performance characterization, the output capacitance change is stable, and the relative capacitance change rate is remarkably improved, so that the detection sensitivity and the anti-interference capability are enhanced. The sensor can be widely applied to the fields of intelligent clothing, man-machine interaction and robots.

Description

Technical Field

[0001] This invention relates to the field of sensors, and in particular to a flexible proximity sensor based on a liquid metal mask spraying process and its fabrication method. Background Technology

[0002] In modern society, flexible electronic devices have shown broad application prospects in wearable devices, human-computer interaction and medical monitoring. Among them, flexible proximity sensors, as an important part of intelligent sensing technology, have received widespread attention and rapid development at home and abroad in recent years.

[0003] Flexible proximity sensors can be categorized into various types based on their sensing principles and mechanisms, including capacitive and triboelectric types. Among these, capacitive and triboelectric sensing technologies have received considerable attention in academic research. The electrode shape of capacitive sensors (such as parallel plates, interdigitated pins, Archimedean spirals, etc.) significantly affects the edge electric field strength and sensor performance (such as signal strength, sensitivity, and signal-to-noise ratio). Triboelectric sensors convert mechanical energy into electrical signals through triboelectric charging and electrostatic induction, but their performance degrades with increasing distance, a problem that urgently needs to be addressed. Therefore, it can be observed that currently researched flexible proximity sensors struggle to balance performance and structural flexibility, leading to challenges in improving sensitivity, flexibility, and adhesion. These trade-offs place higher demands on the development of flexible proximity sensors.

[0004] In existing technologies, liquid metals are often used to fabricate high-performance flexible sensors due to their high conductivity, flexibility, and stability. For example, some studies have explored the fabrication of sensors by injecting liquid metal into hollow elastomer fibers or combining it with ion gel fibers. However, these methods still have limitations in adapting to complex curved surfaces and extreme environments, and there is still room for improvement in terms of device thinning and sensitivity enhancement. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flexible proximity sensor with high sensitivity, good flexibility, thin thickness, strong adhesion and suitable for mass production, as well as its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This application discloses a flexible proximity sensor, including a flexible substrate and concentric interdigitated microelectrodes disposed on the surface of the flexible substrate. The concentric interdigitated microelectrodes are formed from liquid metal through a mask spraying process.

[0007] Preferably, in the above-mentioned flexible proximity sensor, the number of concentric interdigital microelectrodes is 8, the width of each electrode is 0.5 mm, and the electrode spacing is 0.5 mm.

[0008] Preferably, in the above-mentioned flexible proximity sensor, the flexible substrate is made of a novel silicone material composed of polydimethylsiloxane (PDMS).

[0009] Preferably, in the above-mentioned flexible proximity sensor, the liquid metal is a gallium indium alloy (EGaIn).

[0010] Preferably, in the above-mentioned flexible proximity sensor, the total thickness of the sensor is no more than 1 mm, and the thickness of the flexible substrate is no more than 0.5 mm.

[0011] Accordingly, the present invention also discloses a method for manufacturing a flexible proximity sensor, comprising: S1. Prepare a flexible substrate; S2. Fabricate a mask plate with a preset pattern and fix it to the surface of the flexible substrate; S3. Liquid metal is sprayed into the open area of ​​the mask plate using a spray gun to form the concentric interdigitated microelectrodes; S4. Remove the mask plate; S5. Cover the substrate on which the concentric interdigitated microelectrodes are formed with an encapsulation layer and cure it.

[0012] Preferably, in the above-mentioned method for manufacturing a flexible proximity sensor, the process of spraying liquid metal involves controlling the spraying air pressure to be 0.2-0.5 MPa, the spraying distance to be 100-150 mm, and maintaining the spray gun at a constant speed.

[0013] Preferably, in the above-described method for manufacturing a flexible proximity sensor, the curing step is performed at 37°C for 60 minutes.

[0014] Preferably, in the above-described method for manufacturing a flexible proximity sensor, the flexible substrate and encapsulation layer are formed by injecting novel silicone into a 3D-printed mold and curing it.

[0015] Compared with existing technologies, the advantages of this invention are as follows: The flexible proximity sensor of this invention, through mask spraying design process, successfully reduces the sensor thickness to less than 1 mm, significantly improving the sensor's flexibility and adhesion to complex curved surfaces; the optimized concentric interdigitated electrode structure increases the effective surface area and edge electric field strength, resulting in a significant increase in the relative capacitance change rate, improved detection distance and sensitivity, while also possessing excellent anti-interference ability and repeatability; the mask spraying process achieves high-precision and high-efficiency patterning, with controllable key parameters, providing a feasible path for large-scale, low-cost industrial production. Attached Figure Description

[0016] Figure 1 The diagram shown is a structural schematic of the present invention. Figure 2 The image shown is a physical diagram of the present invention. Figure 3 The figure shown is a tensile test diagram of the present invention. Figure 4 The diagram shown is a torsion test diagram of the present invention. Figure 5 The image shown is a test diagram of arm attachment according to the present invention. Figure 6 The figure shown is a curve illustrating the relative capacitance change rate as a function of distance according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] like Figure 1 As shown, the flexible proximity sensor in this embodiment has a size of 20×20×1mm. The middle part is a flexible substrate, and the concentric interdigital microelectrodes on both sides of the flexible substrate are made of liquid metal through the following mask spraying process, with a total of 8 rings and a line width and spacing of 0.5mm.

[0019] The material of the flexible substrate is preferably a novel silicone material composed of polydimethylsiloxane (PDMS), and the thickness of the flexible substrate is no more than 0.5 mm.

[0020] The liquid metal in concentric interdigitated microelectrodes is preferably a gallium-indium alloy (EGaIn), which has the characteristics of high resistivity and good stability.

[0021] The aforementioned concentric interdigitated microelectrode structure exhibits high stability and sensitivity, along with excellent anti-interference capabilities, playing a crucial role in proximity sensing and material analysis in proximity sensors.

[0022] The method for fabricating the ultra-flexible bending sensor in this embodiment of the invention is as follows: S1. Preparation of flexible substrate: First, a set of sensor molds with different heights (0.5mm and 1mm) were fabricated using 3D printing technology to meet the design requirements of the sensor structure. Then, silicone components A and B were mixed evenly in a mass ratio (1:1) and injected into the pre-printed molds. After curing, a flexible thin film substrate with dimensions of 20×20×0.5mm was formed.

[0023] S2. Fabricating the photomask: A laser cutting machine is used to precisely process a stainless steel mask to obtain a template that meets the design requirements of a conductive pattern.

[0024] S3, Spraying liquid metal: The mask is tightly adhered to the cured silicone substrate. Then, using a spray gun, under conditions of 0.3 MPa air pressure and a distance of 120 mm, the open area of ​​the mask is sprayed at a uniform speed until a uniform liquid metal coating is formed. After spraying, the mask is slowly removed to obtain a clear and undamaged liquid metal electrode.

[0025] S4. Solidification and Encapsulation: Place the substrate with electrodes into a 1mm high encapsulation mold, then pour in the mixed silicone again, ensuring complete coverage of the electrodes. Finally, place the entire mold in a 37°C oven for 60 minutes to cure, allowing the encapsulation layer to firmly bond with the substrate, completing the sensor fabrication.

[0026] According to the specific embodiments described above, a flexible proximity sensor can be fabricated. In the actual fabrication process, strict control of material quality and processing precision is necessary to ensure the sensor's performance and stability. Furthermore, relevant safety regulations and operating guidelines should be followed during fabrication to ensure the safety of operators.

[0027] It is worth noting that the above implementation method is only an example, and the actual manufacturing process can be appropriately adjusted and improved as needed. The specific manufacturing steps and parameters can be optimized and adjusted according to the actual situation to obtain the best sensor performance and function.

Claims

1. A flexible tactile sensor, characterized by, The flexible substrate and the concentric interdigital microelectrode formed on the surface of the flexible substrate by a mask spraying process of liquid metal.

2. The flexible proximity sensor of claim 1, wherein: The concentric interdigital microelectrode has 8 turns, each turn has a width of 0.5 mm, and the electrode spacing is 0.5 mm.

3. The flexible proximity sensor of claim 1, wherein: The flexible substrate is made of a new type of silica gel composed of polydimethylsiloxane (PDMS).

4. The flexible proximity sensor of claim 1, wherein: The liquid metal is gallium-indium alloy (EGaIn).

5. The flexible proximity sensor of claim 1, wherein: The total thickness of the sensor is not more than 1 mm, and the thickness of the flexible substrate is not more than 0.5 mm.

6. The method of claim 1 to 5, wherein The sensor comprises: S1, preparing a flexible substrate; S2, making a mask plate with a preset pattern and fixing it on the surface of the flexible substrate; S3, spraying liquid metal in the open area of the mask plate by a spray gun to form the concentric interdigital microelectrode; S4, removing the mask plate; S5, covering the encapsulation layer on the substrate with the concentric interdigital microelectrode and curing.

7. The method of manufacturing according to claim 6, wherein: The process of spraying liquid metal controls the spraying air pressure to be 0.2-0.5 MPa, the spraying distance to be 100-150 mm, and keeps the spray gun moving at a constant speed.

8. The method of claim 6, wherein: The curing step is carried out at 37°C for 60 minutes.

9. The method of claim 6, wherein: The flexible substrate and the encapsulation layer are formed by injecting the new type of silica gel into a 3D printed mold and curing.

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