Flexible temperature and pressure integrated sensor

Abstract

The invention belongs to the related technical field of flexible sensors, and discloses a flexible sensor capable of simultaneously monitoring temperature and pressure and a preparation method thereof, and the flexible sensor sequentially comprises an upper electrode, a flexible dielectric layer with a spatial ordered multistage microstructure, a thin film thermistor and a lower electrode. The flexible dielectric layer with the spatially ordered multistage microstructure is composed of a flexible polymer and comprises a first-stage microstructure and a second-stage microstructure which are orderly arranged on a plane. When pressed by an object, the pressure can be monitored through the capacitance change of the sensor and the temperature can be monitored through the resistance change of the thin film thermistor. The spatial ordered multistage microstructure of the flexible sensor can effectively improve the sensitivity and the measuring range of the sensor.

Description

Technical Field

[0001] This invention relates to a sensor, and more particularly to a flexible sensor capable of simultaneously detecting temperature and pressure, and a method for manufacturing the same. Background Technology

[0002] With the rapid development of the Internet of Things (IoT), smart manufacturing, and smart terminal devices, the demand for high-performance sensors is increasing, especially those capable of simultaneously monitoring multiple physical parameters. In the field of battery health monitoring, simultaneous monitoring of temperature and pressure can provide comprehensive battery status data, helping to detect potential risks in a timely manner and optimize battery life. Flexible robots need to sense changes in temperature and pressure on their surfaces in real time to make precise adjustments when performing complex tasks. In wearable devices, the integration of temperature and pressure sensors can improve the user experience by providing more accurate health data and feedback through continuous monitoring of physiological indicators. However, due to their rigid structure, traditional sensors struggle to provide reliable dual-parameter monitoring in these complex and variable environments.

[0003] This technology proposes a novel flexible temperature and pressure sensor integrating temperature and pressure sensing. It employs microstructure design and new processes to improve the sensor's sensitivity and durability. Based on multi-element fusion sensing technology, it integrates multiple sensing functions such as pressure and temperature, enabling simultaneous monitoring of multiple parameters. The innovations lie in the sensor's flexibility and the microstructure design of the pressure-sensitive dielectric layer, ensuring its adaptability and response performance on different shapes and complex surfaces. The integrated multi-parameter sensing allows for simultaneous monitoring of multiple parameters, improving the accuracy and practicality of data acquisition. Summary of the Invention

[0004] To address existing problems, this invention proposes a flexible temperature and pressure sensor and its fabrication method. This invention designs and fabricates a capacitive sensor with a spatially ordered multi-level microstructure dielectric layer and an embedded thin-film thermistor, enabling simultaneous temperature sensing and pressure detection. This solves the problems of high cost, large measurement space, and complex equipment associated with using two separate sensors. Furthermore, based on the spatially ordered multi-level microstructure of the dielectric layer, the sensor's sensitivity and measurement range can be further improved. The electrodes and dielectric materials of this flexible pressure and temperature sensor are both made of flexible polymer materials, exhibiting high flexibility, small size, simple fabrication process, and low cost, allowing for mass production.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A flexible temperature and pressure sensor includes a flexible FPC upper electrode, a dielectric layer, a thin-film thermistor, and a flexible FPC lower electrode arranged sequentially. The FPC electrode has pre-installed wires for connection to an external data acquisition device. Figure 1 This is a schematic diagram of the sensor structure.

[0007] A 3D printing mold was designed with a primary microstructure consisting of a slanted pyramid with a base and height of 800 μm, and a secondary microstructure with a base side length of 600 μm and a height of 600 μm. The two microstructures are distributed in a planar, ordered, spaced array with a spacing of 800 μm. A mixture of polydimethylsiloxane and graphene was poured into the mold, and after a series of operations, demolding yielded a dielectric layer with a spatially ordered multi-level microstructure, which can effectively improve the sensitivity and range of pressure sensing.

[0008] The advantages of this invention compared to the prior art are:

[0009] (1) By embedding thin film thermal resistors between flexible capacitive sensors, pressure and temperature sensing of flexible sensors can be integrated in a single modular manner.

[0010] (2) By 3D printing, spatially ordered multi-level microstructures are created on the surface of the dielectric layer, thereby achieving simultaneous improvement in range and sensitivity. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the sensor structure.

[0012] Figure 2 This is a picture of the actual sensor.

[0013] Figure 3 This is the pressure-capacitance response curve of the sensor.

[0014] Figure 4 For temperature response testing of the sensor. Detailed Implementation

[0015] The specific implementation method is as follows, which is intended to illustrate the present invention and not to further limit the present invention.

[0016] After 3D printing, the mold with the microstructure is immersed in a beaker of deionized water and then cleaned in an ultrasonic cleaner for five minutes. This step cleans the mold surface and any impurities within the microstructure, facilitating subsequent film preparation. Polydimethylsiloxane (PDMS) and a curing agent are mixed at a mass ratio of 10:1 to obtain a PDMS mixture. The test tube containing the PDMS mixture is placed in a rotary mixer and stirred thoroughly for 10 minutes. Graphene powder, at a mass ratio of 1:50 to the PDMS mixture, is added and stirred until homogeneous. The prepared liquid composite is then uniformly poured into the designed 3D-printed mold and placed in a vacuum dryer. The vacuum pump is turned on to maintain a vacuum inside the dryer, and then turned off. Small bubbles will gradually appear on the sample surface. After the bubbles completely disappear, the vent valve is opened. This process is repeated multiple times until no more bubbles appear on the surface. Due to the small size of the microstructures, this process is crucial to remove residual bubbles from the mold and ensure that the mixture fully fills the microstructures within the mold. The sample was placed in a forced-air drying oven and cured at 80℃ for 60 minutes. After drying, it was removed, cooled, and demolded to obtain a microstructured dielectric layer.

[0017] The thermistor was fabricated using magnetron sputtering. After cleaning the lower electrode of the FPC, the mask and the lower electrode were fixed together in the magnetron sputtering chamber. A cobalt-nickel-iron-based alloy 50Ni-10Co-Fe target was placed, and vacuum sputtering was performed. The thickness of the alloy film was controlled by adjusting the sputtering time. The sputtered alloy film was placed in a high-temperature resistance sintering furnace and annealed. Electrodes were then sputtered onto the alloy film again using magnetron sputtering to obtain the thermistor. PDMS self-encapsulation was achieved based on the van der Waals forces between PDMS molecules. Specifically, the fabricated microstructure film, the upper electrode, and the lower electrode with the embedded thermistor were cleaned using a PLUTOVAC plasma vacuum cleaner, then stacked and bonded sequentially, and further reinforced with adhesive tape to obtain the desired result. Figure 2 sensor.

[0018] To verify the response characteristics of the sensor under different microstructure arrangements, 3D-printed molds with the same two-level microstructures but different spacings were designed, specifically 600µm and 700µm. The above steps were repeated to fabricate the sensor and calibrate the capacitive-pressure response characteristics of the three microstructure spacings. Figure 3 As shown, the smaller the sensor spacing, the higher the sensor sensitivity. The sensor is placed inside an oven to test its temperature, and wires are led out through the oven's guide holes to the temperature acquisition chip. (See figure) Figure 4 As shown, real-time temperature comparison demonstrates that the sensor can respond to temperature changes promptly and accurately.

Claims

1. A flexible temperature and pressure integrated sensor, characterized in that: The device includes an upper electrode, a dielectric layer, a thin-film thermistor, and a lower electrode arranged sequentially. The upper and lower electrodes are flexible FPC electrodes. The dielectric layer has a spatially ordered multi-level microstructure and is composed of a mixture of polydimethylsiloxane and graphene. The thin-film thermistor is made of a cobalt-nickel-iron-based alloy.

2. The flexible temperature and pressure integrated sensor as described in claim 1, characterized in that: The multi-level microstructure of the dielectric layer includes a primary microstructure and a secondary microstructure. The primary microstructure is an oblique pyramid with a base of 800 μm and a height of 800 μm, and the secondary microstructure is an oblique pyramid with a base of 600 μm and a height of 600 μm.

3. The flexible temperature and pressure integrated sensor as described in claim 2, characterized in that: The planar distance between the primary microstructure and the secondary microstructure is 600-800 μm.

4. The flexible temperature and pressure integrated sensor as described in any one of claims 1 to 3, characterized in that: The mass ratio of polydimethylsiloxane to graphene is 50:

1.

5. The flexible temperature and pressure integrated sensor as described in claim 4, characterized in that: The thickness of the thin-film thermistor is 50 nm.

6. A method for fabricating the flexible temperature and pressure integrated sensor according to any one of claims 1 to 5, characterized in that: Includes the following steps: (1) Prepare and clean the 3D printing mold; (2) Mix polydimethylsiloxane, curing agent and graphene, pour into mold, vacuum degas and then cure and demold to obtain dielectric layer; (3) A cobalt-nickel-iron-based alloy thin film is formed on the lower electrode by magnetron sputtering, and a thermistor is obtained by annealing and secondary sputtering. (4) After cleaning the dielectric layer, the upper electrode and the lower electrode with the embedded thermistor, stack and package them.

7. The preparation method according to claim 6, characterized in that: The curing temperature in step (2) is 80°C and the curing time is 60 minutes.

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