A dual-mode flexible capacitive sensor based on phase change regulation and a preparation method thereof

Abstract

The application discloses a dual-mode flexible capacitive sensor based on phase change regulation and a preparation method, and belongs to the technical field of flexible sensors. The method comprises the following steps: preparing a temperature-sensitive phase change composite dielectric layer film, and performing hot pressing and bonding under the condition that the temperature is lower than the melting point of polycaprolactone; and the dual-mode flexible capacitive sensor is subjected to controlled cooling by using different cooling rates. According to the application, the thermal history of the temperature-sensitive phase change composite dielectric layer is eliminated and the controlled cooling is performed after the completion of the assembly of the device, the crystallization kinetics and the thermodynamic competition mechanism of the semi-crystalline polymer under different cooling rates are utilized, the physical reconstruction of the internal microstructure is realized, and therefore the same sensor can be reversibly configured between the high-sensitivity mode and the wide-range mode in situ.

Description

Technical Field

[0001] This invention specifically belongs to the field of flexible sensor technology, and relates to a dual-modal flexible capacitive sensor based on phase change modulation and its fabrication method. Background Technology

[0002] In recent years, flexible capacitive sensors have been widely used in wearable health monitoring, human-computer interaction interfaces, and tactile sensing for intelligent robots due to their advantages such as simple structure, fast response speed, low power consumption, and easy integration with flexible circuits. Their core sensing unit is the dielectric layer between two electrodes, and the microstructure and material properties of the dielectric layer directly determine the sensor's key performance indicators such as sensitivity and detection range.

[0003] In practical applications, different detection tasks have significantly different requirements for sensor performance: for example, in scenarios involving weak physiological signal detection such as pulse monitoring and vocal cord vibration recognition, sensors are required to have extremely high sensitivity and the ability to resolve minute pressures; while in scenarios involving large strains or high pressures such as joint motion monitoring and foot pressure distribution measurement, sensors are required to have a wide detection range and high pressure resistance to avoid premature signal saturation.

[0004] However, once existing flexible capacitive sensors are manufactured, the microstructure and material properties of the dielectric layer are fixed. A single device typically exhibits only fixed sensing characteristics, making it difficult to simultaneously meet the requirements of high sensitivity and wide measurement range. To adapt to the detection requirements of different scenarios, traditional solutions often require redesigning and fabricating sensors with different structures for specific applications, or combining sensors with multiple characteristics through complex array integration. This not only significantly increases the complexity and cost of the manufacturing process but also severely limits the application flexibility of sensors in complex and changing environments. Therefore, realizing a flexible capacitive sensor with in-situ, reversibly switchable sensing characteristics (such as high sensitivity and wide measurement range) without changing the device's hardware structure is of significant practical importance for broadening the application range of flexible sensors and reducing manufacturing costs. To address the above problems, we propose a dual-modal flexible capacitive sensor based on phase transition modulation and its fabrication method. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a dual-modal flexible capacitive sensor based on phase change modulation and its fabrication method. This solves the problems of existing flexible capacitive sensors having a fixed microstructure after molding and the difficulty in achieving both high sensitivity and wide measurement range in a single device.

[0006] This invention is implemented as follows: a method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation, the method comprising: S10, prepare a temperature-sensitive phase change composite dielectric layer film. A polymer solution and a conductive filler suspension are pre-prepared. The conductive filler suspension is added to the polymer solution, followed by the addition of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([EMIM][TFSI]) and polyethylene glycol (PEG-400). After uniform mixing, a composite precursor solution is obtained. The composite precursor solution is then used to form a film and dried to obtain the temperature-sensitive phase change composite dielectric layer film. S20, Obtain the upper and lower electrode layers of the dual-modal flexible capacitive sensor for later use; S30, the surfaces to be bonded, including the upper electrode layer, the lower electrode layer, and the temperature-sensitive phase change composite dielectric film, are subjected to plasma activation treatment; the temperature-sensitive phase change composite dielectric film is sandwiched between the upper electrode layer and the lower electrode layer, and hot-pressed bonded at a temperature below the melting point of polycaprolactone to encapsulate the edge of the device. S40, the assembled bimodal flexible capacitive sensor is heated to a temperature above the melting point of polycaprolactone and held at that temperature to eliminate thermal history; then the bimodal flexible capacitive sensor is subjected to controlled cooling at different cooling rates.

[0007] Preferably, in step S10, when preparing the polymer solution, polycaprolactone is dissolved in dichloromethane to form a polymer solution, while when preparing the conductive filler suspension, multi-walled carbon nanotubes and sodium dodecylbenzene sulfonate are taken and dispersed in dichloromethane to form a conductive filler suspension, wherein the multi-walled carbon nanotubes and sodium dodecylbenzene sulfonate are ultrasonically dispersed and mixed.

[0008] Preferably, in step S10, polycaprolactone is dissolved in dichloromethane to form a polymer solution, wherein the mass fraction of dichloromethane in the polymer solution is 10%, thereby forming a PCL / DCM solution with a mass fraction of 10 wt%. 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and polyethylene glycol are added to the polymer solution under a nitrogen protective atmosphere.

[0009] Preferably, in step S10, when the composite precursor liquid is formed and dried, the composite precursor liquid is poured into a polytetrafluoroethylene mold, and after being allowed to stand at room temperature for volatilization and then vacuum dried, a temperature-sensitive phase change composite dielectric layer film is obtained.

[0010] Preferably, both the upper electrode layer and the lower electrode layer are flexible conductive electrode layers.

[0011] Preferably, the flexible conductive electrode layer is copper foil, aluminum foil, or a flexible printed circuit board.

[0012] Preferably, the flexible conductive electrode layer is a copper foil or a flexible printed circuit board (FPCB).

[0013] Preferably, in step S30, when plasma activation treatment is performed on the surfaces to be bonded of the upper electrode layer, lower electrode layer and temperature-sensitive phase change composite dielectric layer film, the plasma activation treatment conditions are 100W and 30s, the hot pressing bonding conditions are 40℃, 1kPa and 30min, and when the device edge is encapsulated, the device edge is encapsulated with silicone material and cured at room temperature for 24h.

[0014] Preferably, the device edges are encapsulated using Silbione 4717 medical-grade silicone material.

[0015] Preferably, in step S40, when the assembled dual-mode flexible capacitive sensor is heated to a temperature higher than the melting point of polycaprolactone and kept at that temperature, the thermal history elimination condition is to keep it at 70°C for 15 minutes. When controlling the cooling of a dual-mode flexible capacitive sensor using different cooling rates, the cooling rates are divided into slow cooling rates and fast cooling rates. The dual-mode flexible capacitive sensor is configured as a high-sensitivity mode using a slow cooling rate, and as a wide-range mode using a fast cooling rate. The configuration conditions for the high-sensitivity mode are cooling to 25°C at a rate of 1.5°C / min, and the configuration conditions for the wide-range mode are cooling to 25°C at a rate of 12°C / min using air cooling.

[0016] On the other hand, the present invention also provides a dual-mode flexible capacitive sensor based on phase change modulation, the dual-mode flexible capacitive sensor based on phase change modulation includes an upper electrode layer, a lower electrode layer and a temperature-sensitive phase change composite dielectric layer located between the upper electrode layer and the lower electrode layer.

[0017] Preferably, the temperature-sensitive phase change composite dielectric layer comprises the following raw materials in parts by weight: 100 parts of polycaprolactone, 8 parts of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 0.6 parts of multi-walled carbon nanotubes, 6 parts of polyethylene glycol, and 0.12 parts of sodium dodecylbenzenesulfonate.

[0018] Preferably, the polycaprolactone has a molecular weight of 80,000, and the multi-walled carbon nanotubes have a diameter of 10-20 nm and a length of 5-15 μm.

[0019] Preferably, after assembly, the dual-mode flexible capacitive sensor undergoes thermal history elimination and controlled cooling at different cooling rates, enabling it to switch between a high-sensitivity mode and a wide-range mode.

[0020] Compared with the prior art, the embodiments of this application have the following main advantages: This invention achieves physical reconstruction of the internal microstructure by eliminating the thermal history and controlling the cooling of the temperature-sensitive phase-change composite dielectric layer after device assembly. This is achieved by utilizing the competition between the crystallization kinetics and thermodynamics of semi-crystalline polymers at different cooling rates. This allows the same sensor to be configured in situ and reversibly between high-sensitivity and wide-range modes. This method eliminates the need to change the device hardware structure or re-fabricate different types of sensors, significantly improving the application flexibility of the device.

[0021] Furthermore, the dual-modal flexible capacitive sensor prepared by this invention addresses both the needs of weak pressure detection and wide-range detection. In the verified embodiments of this invention, by selecting different cooling rates, the same device can exhibit both a high-sensitivity mode and a wide-range mode. Specifically, the high-sensitivity mode configured with a slow cooling rate is suitable for weak pressure signal detection scenarios such as pulse monitoring and vocal cord vibration; the wide-range mode configured with a fast cooling rate is suitable for detection scenarios with a larger pressure range, such as joint motion monitoring and foot pressure distribution measurement. This broadens the application scenarios of a single device and overcomes the technical bottleneck of the single performance limitation of traditional flexible capacitive sensors.

[0022] The operating mode switching of this invention is based on the thermally reversible phase transition characteristics of a temperature-sensitive phase-change composite dielectric layer. Mode switching is achieved by eliminating the thermal history of the dielectric layer and recooling it. According to the test results of the embodiments of this invention, after 100 mode switching cycles, the sensitivity retention rate of the device is still higher than 90%, indicating that the sensor has excellent mode configuration repeatability and performance retention capabilities. For applications that require both low-voltage high-response detection and a wide detection range, this invention can achieve different operating states through mode switching of the same device, eliminating the need to design and fabricate sensors with different structures for specific applications, and eliminating the need to combine sensors with different characteristics through complex array integration. This reduces the structural complexity and usage costs caused by configuring different sensors to adapt to different scenarios, and has broad application prospects in flexible wearable devices, human-computer interaction, and intelligent robots. Attached Figure Description

[0023] Figure 1 A schematic diagram of the fabrication process of a dual-modal flexible capacitive sensor based on phase transition modulation is shown.

[0024] Figure 2 A schematic diagram of the overall structure of a dual-mode flexible capacitive sensor based on phase change modulation is shown in an embodiment of the present invention.

[0025] Figure 3 The side view of a prototype of a dual-modal flexible capacitive sensor based on phase change modulation is shown in an embodiment of the present invention.

[0026] Figure 4A diagram illustrating the phase transition mechanism of the temperature-sensitive phase transition composite dielectric layer in an embodiment of the present invention is shown.

[0027] Figure 5 The cross-sectional SEM images of the temperature-sensitive phase change composite dielectric layer under different configuration modes in Embodiment 1 of the present invention are shown.

[0028] Figure 6 The pressure-capacitance response characteristic curve in the high-sensitivity mode of Embodiment 1 of the present invention is shown.

[0029] Figure 7 The pressure-capacitance response characteristic curve in the wide range mode of Embodiment 1 of the present invention is shown.

[0030] Figure 8 The diagram shows a comparison of the pressure-capacitance response of the same device before and after switching from A to B to A in Embodiment 1 of the present invention.

[0031] Figure 9 The graph shows the sensitivity retention rate test curve of the dual-mode flexible capacitive sensor in Embodiment 1 of the present invention during 100 reversible switching cycles.

[0032] Figure 10 The diagram shows the basic dynamic performance of the dual-mode flexible capacitive sensor in Embodiment 1 of the present invention.

[0033] Figure 11 A comparative graph showing the overall performance of Example 1 and Comparative Examples 1-4 in this invention is presented.

[0034] Figure 12 The diagram shows the anti-interference test results of the dual-mode flexible capacitive sensor prepared in Embodiment 1 of the present invention under different ambient temperatures.

[0035] Figure 13 The diagram shows the output curve of the dual-mode flexible capacitive sensor prepared in Embodiment 1 of the present invention in a practical application test in high-sensitivity mode.

[0036] Figure 14 The diagram shows the output curve of the dual-mode flexible capacitive sensor prepared in Embodiment 1 of the present invention in a wide-range mode practical application test. Detailed Implementation

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0038] Once manufactured, the microstructure and material properties of the dielectric layer in existing flexible capacitive sensors are fixed. A single device typically exhibits only fixed sensing characteristics, making it difficult to simultaneously meet the demands of high sensitivity and wide measurement range. To adapt to the detection requirements of different scenarios, traditional solutions often require redesigning and fabricating sensors with different structures for specific applications, or combining sensors with multiple characteristics through complex array integration. This not only significantly increases the complexity and cost of the manufacturing process but also severely limits the sensor's application flexibility in complex and variable environments. To address these issues, we propose a dual-modal flexible capacitive sensor based on phase transition modulation and its fabrication method. In summary, the method involves first preparing a temperature-sensitive phase-change composite dielectric layer film, then performing plasma activation treatment on the upper electrode layer 1, lower electrode layer 3, and the surfaces of the temperature-sensitive phase-change composite dielectric layer film to be bonded. The temperature-sensitive phase-change composite dielectric layer film is then sandwiched between the upper electrode layer 1 and the lower electrode layer 3, and hot-pressed at a temperature below the melting point of polycaprolactone. The assembled dual-mode flexible capacitive sensor is then heated to a temperature above the melting point of polycaprolactone and held at this temperature to eliminate thermal history. Subsequently, the dual-mode flexible capacitive sensor is subjected to controlled cooling at different cooling rates. This invention, by eliminating thermal history and controlling cooling of the temperature-sensitive phase-change composite dielectric layer 2 after device assembly, utilizes the competition mechanism between the crystallization kinetics and thermodynamics of semi-crystalline polymers at different cooling rates to achieve physical reconstruction of the internal microstructure. This allows the same sensor to be configured in situ and reversibly between high-sensitivity and wide-range modes. This invention requires no hardware replacement, has a simple process, good repeatability, and application flexibility, and has broad application prospects in flexible wearable devices, human-computer interaction, and intelligent robots.

[0039] For ease of description, in the embodiments of this invention, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is referred to as [EMIM][TFSI], multi-walled carbon nanotubes are referred to as MWCNTs, polycaprolactone is referred to as PCL, polyethylene glycol is referred to as PEG-400 in the specific embodiments of this application, and sodium dodecylbenzenesulfonate is referred to as SDBS. The above abbreviations are for convenience only and do not change the specific meaning of each component. Unless otherwise specified, the above English abbreviations appearing in the embodiments of this invention refer to the corresponding specific chemical substances and do not constitute new technical features or limitations.

[0040] This invention provides a dual-mode flexible capacitive sensor based on phase change modulation. The dual-mode flexible capacitive sensor includes an upper electrode layer 1, a lower electrode layer 3, and a temperature-sensitive phase change composite dielectric layer 2 located between the upper electrode layer 1 and the lower electrode layer 3. The upper electrode layer 1, the temperature-sensitive phase change composite dielectric layer 2, and the lower electrode layer 3 are stacked sequentially and together form a layered sensitive unit that can generate a capacitive response under pressure. After the device is assembled, the temperature-sensitive phase change composite dielectric layer 2 can be reconstructed through thermal history elimination and controlled cooling, enabling the same sensor to switch in situ between a high-sensitivity mode and a wide-range mode.

[0041] The temperature-sensitive phase change composite dielectric layer 2 is composed of a semi-crystalline polymer matrix, an ionic liquid, a conductive filler, a plasticizer, and a dispersant. In the verified embodiments of this invention, the semi-crystalline polymer matrix is ​​PCL, the ionic liquid is [EMIM][TFSI], the conductive filler is MWCNTs, the plasticizer is PEG, preferably PEG-400, and the dispersant is SDBS. These materials together constitute the temperature-sensitive phase change composite dielectric layer 2. PCL provides a basis for the reversible melt-crystallization transition, [EMIM][TFSI] improves the dielectric response of the temperature-sensitive phase change composite dielectric layer 2, MWCNTs improve the dielectric properties of the temperature-sensitive phase change composite dielectric layer 2 and enhance system stability, PEG-400 improves the flexibility of the temperature-sensitive phase change composite dielectric layer 2, and SDBS improves the uniformity of MWCNTs dispersion in the system.

[0042] in, Figure 2 This illustration shows a schematic diagram of the overall structure of a dual-modal flexible capacitive sensor based on phase change modulation in an embodiment of the present invention. Furthermore, this embodiment also provides a method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation. Figure 1 A schematic diagram illustrating the fabrication process of a dual-modal flexible capacitive sensor based on phase transition modulation is shown. The fabrication method specifically includes: S10, Preparation of a temperature-sensitive phase change composite dielectric layer film: The temperature-sensitive phase change composite dielectric layer 2 comprises the following raw materials in parts by weight: 100 parts of polycaprolactone, 8 parts of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 0.6 parts of multi-walled carbon nanotubes, 6 parts of polyethylene glycol, and 0.12 parts of sodium dodecylbenzenesulfonate; In the preparation of the temperature-sensitive phase change composite dielectric layer film, a polymer solution and a conductive filler suspension are first prepared. The conductive filler suspension is added to the polymer solution, and then 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([EMIM][TFSI]) and polyethylene glycol (PEG-400) are added and mixed evenly to obtain a composite precursor solution; the composite precursor solution is formed into a film and dried to obtain a temperature-sensitive phase change composite dielectric layer film; In the preparation of the polymer solution, polycaprolactone is dissolved in dichloromethane to form a polymer solution. In the preparation of the conductive filler suspension, multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are dispersed in dichloromethane to form a conductive filler suspension. The multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate are ultrasonically dispersed and mixed. The polycaprolactone is dissolved in dichloromethane to form a polymer solution with a dichloromethane mass fraction of 10%, thus forming a 10 wt% PCL / DCM solution. 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and polyethylene glycol are added to the polymer solution under a nitrogen protective atmosphere. The polycaprolactone has a molecular weight of 80,000, and the multi-walled carbon nanotubes have a diameter of 10-20 nm and a length of 5-15 μm.

[0043] It should be noted that when the composite precursor liquid is formed and dried, the composite precursor liquid is poured into a polytetrafluoroethylene mold, and after being allowed to stand at room temperature for volatilization and then vacuum dried, a temperature-sensitive phase change composite dielectric layer film is obtained.

[0044] S20, Obtain the upper electrode layer 1 and lower electrode layer 3 of the dual-mode flexible capacitive sensor for later use. Both the upper electrode layer 1 and the lower electrode layer 3 are flexible conductive electrode layers. The flexible conductive electrode layer can be copper foil, aluminum foil, flexible printed circuit board or other flexible conductive materials. In this embodiment, the flexible conductive electrode layer is preferably copper foil or flexible printed circuit board (FPCB).

[0045] S30, Surface treatment, assembly, and optional encapsulation: Plasma activation treatment is performed on the surfaces to be bonded, including the upper electrode layer 1, the lower electrode layer 3, and the temperature-sensitive phase change composite dielectric film; the temperature-sensitive phase change composite dielectric film is sandwiched between the upper electrode layer 1 and the lower electrode layer 3, and hot-pressed at a temperature below the melting point of polycaprolactone, and the device edges are encapsulated; wherein, when plasma activation treatment is performed on the surfaces to be bonded, including the upper electrode layer 1, the lower electrode layer 3, and the temperature-sensitive phase change composite dielectric film, the plasma activation conditions are 100W for 30s, and the hot-pressing conditions are 40℃, 1kPa, and 30min; when encapsulating the device edges, silicone material is used for encapsulation and cured at room temperature for 24h.

[0046] S40, In-situ configuration of the operating mode: The assembled bimodal flexible capacitive sensor is heated to a temperature above the melting point of polycaprolactone and held at that temperature to eliminate thermal history; then the bimodal flexible capacitive sensor is cooled in a controlled manner using different cooling rates.

[0047] In this embodiment of the invention, when the assembled dual-modal flexible capacitive sensor is heated to a temperature higher than the melting point of polycaprolactone and held at that temperature, the thermal history elimination condition is to hold at 70°C for 15 minutes. When a dual-modal flexible capacitive sensor is subjected to controlled cooling at different rates, these rates are categorized as slow and fast. The slow cooling rate configures the sensor in high-sensitivity mode, while the fast cooling rate configures it in wide-range mode. The high-sensitivity mode is configured by cooling to 25°C at a rate of 1.5°C / min, while the wide-range mode is configured by cooling to 25°C via air cooling at a rate of 12°C / min. Switching between the high-sensitivity and wide-range modes is achieved by repeatedly performing thermal history elimination and reselecting the cooling rate.

[0048] This invention eliminates the thermal history of the temperature-sensitive phase-change composite dielectric layer 2 and performs controlled cooling after device assembly. By utilizing the competition mechanism between the crystallization kinetics and thermodynamics of the semi-crystalline polymer at different cooling rates, the internal microstructure is physically reconstructed. This allows the same sensor to be configured in situ and reversibly between high-sensitivity mode and wide-range mode. This invention does not require changing the hardware structure, has a simple process, good repeatability and application flexibility, and has broad application prospects in flexible wearable devices, human-computer interaction and intelligent robots.

[0049] In a further preferred embodiment of the present invention, the method for preparing a temperature-sensitive phase change composite dielectric thin film specifically includes: S101, Polymer matrix dissolution: PCL is dissolved in an organic solvent to obtain a polymer solution. In the verified embodiments of this invention, dichloromethane is selected as the organic solvent. Dichloromethane has good dissolving ability for PCL and is easy to remove through subsequent evaporation. S102, Dispersion of conductive fillers: MWCNTs and SDBS are added to an appropriate amount of organic solvent for dispersion treatment to obtain a conductive filler suspension. To improve the dispersion effect of MWCNTs in the system, ultrasonic dispersion can be used for pretreatment. S103, Multi-component mixing: The conductive filler suspension is added to the polymer solution for mixing, followed by the addition of [EMIM][TFSI] and PEG-400, and continuous stirring is performed to ensure uniform mixing of all components, resulting in a composite precursor solution. In the verified embodiments of this invention, the addition of the ionic liquid and plasticizer is carried out under a protective atmosphere, preferably slowly under a nitrogen protective atmosphere; the stirring process can be carried out in stages, i.e., stirring at room temperature first, followed by appropriate heating and continued stirring, to improve the mixing uniformity of the multi-component system, wherein the heating and stirring temperature is preferably 35-45°C, more preferably 40°C; S104, Film Formation and Drying: The uniformly mixed composite precursor liquid is injected into a mold for molding and then dried to remove the solvent from the system, resulting in a temperature-sensitive phase change composite dielectric layer film. In the verified embodiment of this invention, the mold is a polytetrafluoroethylene mold. The drying process includes room temperature settling and vacuum drying. The room temperature settling time can be adjusted according to the solvent evaporation, preferably 18-30 h, more preferably 24 h. The vacuum drying temperature is preferably 35-45 °C, more preferably 40 °C. The vacuum drying time is preferably 36-60 h, more preferably 48 h. After the above treatment, a temperature-sensitive phase change composite dielectric layer film with a complete structure that meets the requirements of subsequent assembly can be obtained. The film thickness can be adjusted according to the baseline capacitance and pressure response requirements of the target device. In the verified embodiment of this invention, the obtained film thickness is approximately 500 μm. In a further preferred embodiment of the present invention, when acquiring the upper electrode layer 1 and the lower electrode layer 3 of the dual-modal flexible capacitive sensor, the following operations are performed: S201, Electrode layer preparation. An upper electrode layer 1 and a lower electrode layer 3 are provided. In this invention, both the upper electrode layer 1 and the lower electrode layer 3 are flexible conductive electrode layers. The flexible conductive electrode layer can be made of copper foil, aluminum foil, flexible printed circuit board, or other flexible conductive materials, preferably copper foil or FPCB; S202, Electrode layer cutting and lead-out terminal provision: The flexible conductive electrode layer is cut according to the target device size, and electrical connection leads are provided for subsequent connection with external test circuits. Using the aforementioned flexible conductive electrode layer helps improve the structural stability and electrical connection reliability of the device during bending, pressure, and repeated use.

[0050] In a further preferred embodiment of the present invention, the surface treatment, assembly, and optional packaging method includes: S301, Surface activation treatment. Surface activation treatment is performed on the surfaces of the upper electrode layer 1, lower electrode layer 3, and the temperature-sensitive phase change composite dielectric layer film to be bonded. In the verified embodiments of this invention, the surface activation treatment employs plasma activation treatment. The plasma activation power is preferably 80-120W, more preferably 100W; the treatment time is preferably 20-40s, more preferably 30s. Surface activation treatment is beneficial for improving the interlayer bonding effect. S302, hot-press bonding: The treated temperature-sensitive phase change composite dielectric layer film is sandwiched between the upper electrode layer 1 and the lower electrode layer 3, and hot-pressed bonding is performed at a temperature below the melting point of PCL to form a stable laminated structure. The hot-press bonding temperature is preferably 3-50℃, more preferably 40℃; the bonding pressure is preferably 0.5-5kPa, more preferably 1kPa; the bonding time is preferably 10-60min, more preferably 30min. Controlling the hot-press bonding temperature below the melting point of PCL helps to avoid significant melting of the temperature-sensitive phase change composite dielectric layer 2 during assembly. S303, edge-sealed encapsulation: After bonding, the edges of the device can be encapsulated according to usage requirements. In the verified embodiments of this invention, the edge encapsulation material can be a silicone-based material, preferably medical-grade silicone, and more preferably Silbione 4717 medical-grade silicone. After encapsulation, it can be cured at room temperature, with a curing time preferably 12-36 hours, more preferably 24 hours. Edge sealing improves the overall structural integrity of the device and helps enhance its stability during use.

[0051] In a further preferred embodiment of the present invention, the in-situ configuration method of the working mode specifically includes: S401, Thermal history elimination: The assembled sensor is heated to a temperature higher than the melting point of PCL and held at that temperature for a period of time to eliminate the thermal history, allowing the temperature-sensitive phase change composite dielectric layer 2 to enter a reconfigurable state. The heating temperature is preferably 65-80℃, more preferably 70℃; the holding time is preferably 10-30 min, more preferably 15 min. S402, High Sensitivity Mode Configuration: When the sensor needs to be configured in high sensitivity mode, after thermal history elimination is completed, the sensor is slowly cooled to room temperature or the target operating temperature. The cooling rate of the slow cooling is preferably 1-3℃ / min, more preferably 1.5℃ / min; S403, wide-range mode configuration: When the sensor needs to be configured in wide-range mode, after thermal history elimination is completed, the sensor is rapidly cooled to room temperature or the target operating temperature. The cooling rate is preferably 8-15℃ / min, more preferably 12℃ / min; S404, Mode Switching: The two operating modes described above can be switched by reheating to eliminate thermal history and reselecting the cooling rate. In the verified embodiment of this invention, the cooling endpoint is 25°C. This method allows the same device to switch in situ between high-sensitivity mode and wide-range mode without changing the device structure.

[0052] In summary, the above preparation and pattern configuration methods can yield [the desired results]. Figure 2 The dual-mode flexible capacitive sensor shown can switch in situ between a high-sensitivity mode and a wide-range mode.

[0053] Example 1

[0054] This invention provides a dual-mode flexible capacitive sensor based on phase change modulation. The overall structure of the sensor is as follows: Figure 2 As shown, it includes an upper electrode layer 1 and a lower electrode layer 3 arranged opposite to each other, and a temperature-sensitive phase-change composite dielectric layer 2 located between the upper electrode layer 1 and the lower electrode layer 3. By implementing thermal history elimination and differentiated cooling configuration on the temperature-sensitive phase-change composite dielectric layer 2, the same device can be switched in situ between a high-sensitivity mode and a wide-range mode.

[0055] In this embodiment of the invention, the method for fabricating a dual-modal flexible capacitive sensor based on phase transition modulation specifically includes: S10 was used to prepare a temperature-sensitive phase change composite dielectric thin film.

[0056] S101, Polymer matrix dissolution: Weigh 10g of PCL particles and add them to 90g of dichloromethane. Dissolve them completely under magnetic stirring to obtain a PCL / DCM solution (i.e., polymer solution) with a mass fraction of 10wt%.

[0057] S102, Dispersion of conductive filler: Weigh 0.06g MWCNTs and 0.012g SDBS, add them to 10mL dichloromethane, and disperse by ultrasonication for 45min to obtain MWCNTs suspension (i.e. conductive filler suspension).

[0058] S103, Multi-component mixing: The MWCNTs suspension was added to the PCL / DCM solution and mechanically stirred for 30 min; then, under a nitrogen protective atmosphere, 0.8 g of [EMIM][TFSI] and 0.6 g of PEG-400 premixed solution was slowly added dropwise at a rate of 0.5 mL / min using a syringe pump; after the addition was completed, mechanical stirring was continued at room temperature for 2 h, and then the temperature was raised to 40 °C and stirred for another 1 h to obtain a uniformly mixed composite precursor solution.

[0059] S104, Film Formation and Drying: The composite precursor liquid is poured into a polytetrafluoroethylene mold with dimensions of 50mm×50mm×10mm and left to stand at room temperature for 24h to allow dichloromethane to evaporate; then, the preliminarily formed film is transferred to a vacuum oven at 40℃ and dried for another 48h to remove residual solvent, resulting in a temperature-sensitive phase change composite dielectric layer film with a thickness of approximately 500μm.

[0060] S20, prepare the upper electrode layer 1 and the lower electrode layer 3.

[0061] S201, Electrode layer preparation: Cut two copper foils, each 50mm×50mm in size, to serve as the upper electrode layer 1 and the lower electrode layer 3, respectively.

[0062] S202, Lead-out terminal reserved: During the cutting process, an electrical connection lead-out terminal is reserved for subsequent connection with external test circuits.

[0063] S30, Surface treatment, assembly and packaging.

[0064] S301, Surface activation treatment: Plasma activation treatment is performed on the conductive surfaces of the two copper foils and the upper and lower surfaces of the temperature-sensitive phase change composite dielectric layer film. The treatment conditions are 100W and 30s.

[0065] S302, Hot pressing: The temperature-sensitive phase change composite dielectric layer film is sandwiched between the upper electrode layer 1 and the lower electrode layer 3, and hot-pressed for 30 minutes at 40°C and 1 kPa in a flatbed hot press to form a laminated structure.

[0066] S303, edge-sealed encapsulation. The device edges were encapsulated using Silbione 4717 medical-grade silicone and cured at room temperature for 24 hours, resulting in a dual-modal flexible capacitive sensor. The side view morphology of the obtained dual-modal flexible capacitive sensor sample is shown below. Figure 3 As shown, the device has a layered structure, with the upper electrode layer 1, the temperature-sensitive phase change composite dielectric layer 2, and the lower electrode layer 3 stacked in sequence. The device is relatively thin and has flexible and bendable characteristics.

[0067] S40, operating mode configuration.

[0068] S401, Thermal History Elimination: Place the assembled sensor on a temperature control platform, heat it to 70°C and keep it at that temperature for 15 minutes to eliminate thermal history.

[0069] S402, High Sensitivity Mode Configuration: When a high sensitivity mode is required, after thermal history elimination is completed, the temperature is reduced to 25°C at a rate of 1.5°C / min to obtain the slow-cooling configuration sample of Example 1.

[0070] S403, Wide Range Mode Configuration: When a wide range mode is required, after completing the elimination of thermal history, the sample is cooled to 25°C at a rate of approximately 12°C / min using an air-cooling device, thereby obtaining the fast-cooling configuration sample of Example 1.

[0071] S404, Mode Switching: By repeatedly performing thermal history elimination and differential cooling processes, the same sensor can be switched between high sensitivity mode and wide range mode.

[0072] This invention achieves physical reconstruction of the internal microstructure by eliminating the thermal history and controlling the cooling of the temperature-sensitive phase-change composite dielectric layer 2 after device assembly. This is achieved by utilizing the competition mechanism between the crystallization kinetics and thermodynamics of the semi-crystalline polymer at different cooling rates, enabling the same sensor to be configured in situ and reversibly between high-sensitivity and wide-range modes. This method eliminates the need to change the device hardware structure or re-fabricate different types of sensors, significantly improving the application flexibility of the device.

[0073] Furthermore, the dual-modal flexible capacitive sensor prepared by this invention addresses both the needs of weak pressure detection and wide-range detection. In the verified embodiments of this invention, by selecting different cooling rates, the same device can exhibit both a high-sensitivity mode and a wide-range mode. Specifically, the high-sensitivity mode configured with a slow cooling rate is suitable for weak pressure signal detection scenarios such as pulse monitoring and vocal cord vibration; the wide-range mode configured with a fast cooling rate is suitable for detection scenarios with a larger pressure range, such as joint motion monitoring and foot pressure distribution measurement. This broadens the application scenarios of a single device and overcomes the technical bottleneck of the single performance limitation of traditional flexible capacitive sensors.

[0074] The operating mode switching of this invention is based on the thermally reversible phase transition characteristics of the temperature-sensitive phase-change composite dielectric layer 2. Mode switching can be achieved by eliminating the thermal history of the dielectric layer and recooling it. According to the test results of the embodiment of this invention, after 100 mode switching cycles, the sensitivity retention rate of the device is still higher than 90%, indicating that the sensor has excellent mode configuration repeatability and performance retention capability. For application scenarios that require both low-voltage high-response detection and a wide detection range, this invention can achieve different operating states through mode switching of the same device, without the need to design and manufacture sensors with different structures for specific applications, or to combine sensors with different characteristics through complex array integration. This reduces the structural complexity and usage cost caused by configuring different sensors to adapt to different scenarios, and has broad application prospects in flexible wearable devices, human-computer interaction, and intelligent robots.

[0075] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that PEG-400 is not added in step S103. All other raw material composition, film-forming conditions, assembly conditions, thermal history elimination conditions, cooling configuration conditions, and testing conditions are the same as in Example 1. The obtained samples were used for structural characterization and sensing performance testing.

[0076] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that SDBS is not added in step S102. All other raw material composition, film-forming conditions, assembly conditions, thermal history elimination conditions, cooling configuration conditions, and testing conditions are the same as in Example 1. The obtained samples were used for structural characterization and sensing performance testing.

[0077] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that no thermal history erasure treatment or controlled cooling mode configuration was performed after assembly. All other raw material composition, film-forming conditions, assembly conditions, and testing conditions were the same as in Example 1. The resulting sample was directly subjected to structural characterization and sensing performance testing. This sample also served as an initial state reference sample without mode configuration.

[0078] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that although heat treatment was performed after assembly, controlled cooling was not used for mode configuration; instead, the samples were cooled to room temperature under natural conditions. All other raw material composition, film-forming conditions, assembly conditions, and testing conditions were the same as in Example 1. The resulting samples were then subjected to sensing performance testing.

[0079] To avoid ambiguity, in this application, the term "low-pressure response sensitivity" refers to the slope of the linear fit of the curve of relative capacitance change rate (ΔC / C0) versus applied pressure (P) within the corresponding test range. Figure 6 and Figure 7 The vertical axis is expressed as a percentage, therefore the unit of the corresponding pressure response sensitivity is % / kPa. It should be noted that the pressure response sensitivities of the high-sensitivity mode and the wide-range mode were obtained by fitting within their respective target operating ranges, and the relevant values ​​are used to characterize the response capability of each mode within the target application range.

[0080] Performance testing and characterization: The samples prepared in Example 1 and Comparative Examples 1-4 were subjected to morphological observation, thermal analysis, crystal structure characterization, pressure-capacitance response testing, mode switching testing, dynamic performance testing, environmental temperature testing, and application demonstration testing. The results are as follows: Figures 4-14 As shown.

[0081] in, Figure 4 The diagram illustrating the phase transition mechanism of the temperature-sensitive phase-change composite dielectric layer 2 in this embodiment of the invention is shown. To further verify the structural reconstruction mechanism of the temperature-sensitive phase-change composite dielectric layer 2 under different configuration modes, thermal analysis and crystal structure characterization were performed on the samples of Example 1 with slow cooling configuration (i.e., the dual-mode flexible capacitive sensor is configured in high-sensitivity mode with a slow cooling rate), the sample of Example 1 with fast cooling configuration (i.e., the dual-mode flexible capacitive sensor is configured in wide-range mode with a rapid cooling rate), and the sample of Comparative Example 3. Figure 4 (a) shows the DSC curves of the slow-cooling configuration sample of Example 1, the fast-cooling configuration sample of Example 1, and the sample of Comparative Example 3. Figure 4 (b) shows the XRD patterns of the slow-cooling configuration sample of Example 1, the fast-cooling configuration sample of Example 1, and the sample of Comparative Example 3. Figure 4 As shown in (a), the DSC curves indicate that different samples exhibit distinguishable thermal transition characteristics. Compared to the fast-cooling configuration sample of Example 1, the melt-related peak of the slow-cooling configuration sample of Example 1 is more pronounced and the peak shape is relatively concentrated; the DSC curve of the sample of Comparative Example 3 is generally between the two. This result indicates that different cooling histories affect the thermal transition behavior of the temperature-sensitive phase change composite dielectric layer 2, thereby leading to differences in the internal microstructure state. Figure 4 As shown in (b), the XRD pattern further indicates that the characteristic diffraction peaks of the slow-cooled sample in Example 1 are clearer and the peak shapes are relatively sharper; the corresponding peak shapes of the fast-cooled sample in Example 1 show a certain degree of broadening; and the sample in Comparative Example 3 is generally between the two. The above results show that thermal history elimination and differentiated cooling processes can affect the formation mode and perfection of the microcrystalline structure inside the temperature-sensitive phase change composite dielectric layer 2, thus providing a structural basis for the differences in sensing performance under different operating modes.

[0082] Figure 5 The following are cross-sectional SEM images of the temperature-sensitive phase-change composite dielectric layer 2 under different configuration modes in Embodiment 1 of the present invention. Figure 5Image (a) is a cross-sectional SEM image of the slow-cooled sample from Example 1 in high-sensitivity mode. Figure 5 Image (b) is a cross-sectional SEM image of the rapid-cooling configuration sample from Example 1 in wide-range mode, as shown below. Figure 5 As shown, the cross-sectional micromorphology of the temperature-sensitive phase change composite dielectric layer 2 varies significantly under different mode configurations. Figure 5 (a) in the image corresponds to the cross-sectional SEM image of the slow-cooled sample in Example 1 in high-sensitivity mode. A more obvious spherulite structure can be observed, and groove regions can be seen between adjacent structures. Figure 5 (b) in the image corresponds to the cross-sectional SEM image of the rapid-cooling configuration sample in Example 1 under wide-range mode. It is evident that large-sized spherulite structures are significantly reduced, and the overall sample exhibits a relatively dense and uniform fine-grained morphology. Combined with... Figure 4 and Figure 5 This demonstrates that different cooling methods can lead to the formation of differentiated microstructure states within the temperature-sensitive phase change composite dielectric layer 2.

[0083] in, Figure 6 The diagram shows the pressure-capacitance response characteristics in the high-sensitivity mode (i.e., slow-cooling configuration) of Embodiment 1 of the present invention. Figure 7 The diagram shows the pressure-capacitance response characteristic curves under the wide-range mode (i.e., rapid cooling configuration) of Embodiment 1 of the present invention. Regarding pressure response performance, as... Figure 6 As shown, the slow-cooled sample in Example 1 exhibits a significant change in capacitance response within the 0-10 kPa pressure range under high-sensitivity mode. Under the test conditions of this example, fitting its pressure-capacitance response curve yields a slope of approximately 6.68, indicating high pressure response sensitivity in this mode and its applicability for signal detection in lower pressure ranges. Figure 7 As shown, the sample with rapid cooling configuration in Example 1 maintained a stable response in the 0-100kPa pressure range under wide range mode. Under the test conditions of this example, its pressure-capacitance response curve was fitted, and the slope was found to be approximately 0.356, indicating that the sensitivity was relatively reduced in this mode, but the detection range was significantly widened, making it more suitable for detection scenarios with a larger pressure range.

[0084] To illustrate the reversible switching capability of the same device between different modes, the same numbered device in Example 1 was repeatedly configured and tested in mode A → mode B → mode A. Figure 8 The following diagram shows a comparison of the pressure-capacitance response of the same device before and after switching from A to B to A in Embodiment 1 of the present invention. During the switching from A mode to B mode to A mode, the first A mode is the first slow cooling configuration (A1), the B mode is the fast cooling configuration (B), and the second A mode is the second slow cooling configuration (A2). The results are as follows... Figure 8As shown, the device exhibits an A1 response characteristic after the first slow cooling configuration; after reheating to eliminate the thermal history and implementing a rapid cooling configuration, the device switches to a B response characteristic; after further eliminating the thermal history and re-implementing the slow cooling configuration, the device's pressure-capacitance response curve recovers to an A2 trend similar to the initial A1 state. This demonstrates that the dual-mode switching described in this invention does not originate from irreversible damage or a one-time structural change, but rather from the reversible reconstruction of the temperature-sensitive phase-change composite dielectric layer 2 under different cooling histories. Therefore, the same device can perform in-situ, reversible switching between different modes.

[0085] To evaluate the performance retention capability during mode switching, the device in Example 1 was subjected to 100 mode switching cycles. Figure 9 The following is a graph showing the sensitivity retention rate test curve of the dual-modal flexible capacitive sensor in Embodiment 1 of the present invention during 100 reversible switching cycles. The results are as follows: Figure 9 As shown, after 100 mode switching cycles, the sensitivity retention rate of the dual-mode flexible capacitive sensor is still above 90%, indicating that the dual-mode flexible capacitive sensor has good repeatable mode configuration capability and performance retention capability. Figure 9 The tests shown primarily reflect the device's performance retention under repeated hot programming and mode switching conditions.

[0086] To evaluate the service stability of the device under actual repeated stress, dynamic performance tests were conducted on the sample from Example 1. Figure 10 The diagram shows the basic dynamic performance of the dual-modal flexible capacitive sensor in Embodiment 1 of the present invention. Figure 10 (a) in the figure is the loading-unloading hysteresis curve of the dual-mode flexible capacitive sensor. Figure 10 (b) in the figure is the response / recovery time curve of the dual-mode flexible capacitive sensor. Figure 10 (c) in the figure shows the stability diagram of the dual-mode flexible capacitive sensor after 1000 cycles. Figure 10 As shown in (a), the response hysteresis loop formed by the sample of Example 1 during loading and unloading is small, indicating that the device has low hysteresis characteristics and good pressure recovery capability. The overall trend of the loading and unloading curves is consistent, indicating that the device has good response repeatability during cyclic stress. Figure 10 As shown in (b), under step pressure, the sample of Example 1 can complete the response in a short time and quickly recover to the initial state after unloading, demonstrating good dynamic detection capability. During multiple consecutive load-unload processes, the response waveform maintains good repeatability, indicating that the device has good transient response stability. Figure 10As shown in (c), after 1000 cycles of loading under fixed pressure, the peak output of the sample in Example 1 fluctuated to a certain extent, but the overall trend was stable, and no obvious failure or abnormal change was observed. This indicates that the sensor of the present invention has good cyclic stability and structural durability under repeated loading conditions. Figure 10 The test shown primarily reflects the dynamic service performance of the device under repeated loading of a fixed external force, and... Figure 9 The mode switching cycle retention rate test shown corresponds to different evaluation dimensions.

[0087] To facilitate the explanation of the differences in key evaluation parameters between Example 1 and the comparative samples, Table 1 lists the original evaluation parameters and relative retention rates of Example 1 and Comparative Examples 1-4. The low-pressure response sensitivity is taken as the slope of the linear fit of the relative capacitance change rate-pressure curve for each sample within the corresponding low-pressure test range; the upper limit of the effective range is taken as the highest detection pressure of the sample under stable and resolvable response conditions. In Table 1, SH represents the low-pressure response sensitivity in high-sensitivity mode, which is the slope of the linear fit of the relative capacitance change rate (ΔC / C0)-pressure (P) curve for the sample within the 0-10 kPa range, in % / kPa; RW represents the upper limit of the effective range in wide-range mode, in kPa. The "relative retention rate of low-pressure response sensitivity" and "relative retention rate of effective range" in the table represent the degree of retention of each sample relative to Example 1 in the corresponding evaluation parameters.

[0088] Table 1. Key evaluation parameters for dual-modal operation in Example 1 and Comparative Examples 1-4 sample SH Relative retention rate of low-pressure response sensitivity / % RW Relative retention rate of effective range / % Example 1 6.68 100 97 100 Comparative Example 1 2.34 35 35 36 Comparative Example 2 3.07 46 50 52 Comparative Example 3 1.40 21 23 24 Comparative Example 4 1.87 28 41 42 To further illustrate the crucial role of the material formulation and mode configuration process in achieving dual-modal performance in this invention, a comparative test of the comprehensive dual-modal performance was conducted between Example 1 and Comparative Examples 1-4; among them, Figure 11 A comparative graph showing the overall performance of Example 1 and Comparative Examples 1-4 in this invention is shown, wherein... Figure 11 The blue bars represent the relative retention rate of low-pressure response sensitivity, and the red bars represent the relative retention rate of the effective range. It should be noted that... Figure 11A dual-index comprehensive evaluation method was adopted. In the high-sensitivity mode, the low-pressure response sensitivity was used as the representative evaluation parameter, while in the wide-range mode, the upper limit of the effective range was used as the representative evaluation parameter. Therefore, the two sets of bar charts correspond to the performance retention of the dual-modal sensor under the two target operating modes, respectively. For easy comparison, the low-pressure response sensitivity of Example 1 in the 0-10 kPa range under the high-sensitivity mode was used as the normalization benchmark and set to 100%; simultaneously, the upper limit of the effective range of Example 1 in the wide-range mode was used as the normalization benchmark and set to 100%. Under the test conditions of this example, the low-pressure response sensitivity of Example 1 in the high-sensitivity mode was 6.68% / kPa, and the upper limit of the effective range in the wide-range mode was approximately 97 kPa.

[0089] Test results show that Example 1 outperforms all comparative samples in both high-sensitivity mode and wide-range mode. Comparative Example 1, lacking PEG-400, exhibits reduced flexibility and compressive deformation capability of its temperature-sensitive phase-change composite dielectric layer 2, resulting in a low-pressure response sensitivity of only 2.34% / kPa in high-sensitivity mode and an effective range limit of approximately 35kPa in wide-range mode, corresponding to relative retention rates of 35% and 36%, respectively. Comparative Example 2, lacking SDBS, suffers from poor dispersion uniformity of the conductive filler in the system, resulting in a low-pressure response sensitivity of approximately 3.07% / kPa in high-sensitivity mode and an effective range limit of approximately 50kPa in wide-range mode, corresponding to relative retention rates of 46% and 52%, respectively. Comparative Example 3, lacking thermal history elimination treatment, struggles to enter a stable reconfigurable state in its dielectric layer, resulting in a low-pressure response sensitivity of approximately 1.40% / kPa in high-sensitivity mode and an effective range limit of approximately 23kPa in wide-range mode, corresponding to relative retention rates of 21% and 24%, showing the most significant performance degradation. Although Comparative Example 4 was heated, it was not cooled in a controlled manner for mode configuration. Instead, it was cooled in a natural environment, making it difficult to form a stable and distinguishable mode structure. Its low-pressure response sensitivity in high-sensitivity mode was about 1.87% / kPa, and the effective range limit in wide-range mode was about 41kPa, corresponding to relative retention rates of 28% and 42%, respectively.

[0090] The above results demonstrate that the technical effectiveness of this invention does not stem from a single material factor or a single post-processing factor, but rather from the synergistic effect of material composition and mode configuration processes. PEG-400, SDBS, thermal history elimination, and controlled cooling all play crucial roles in achieving reversible switching between high-sensitivity and wide-range modes, and none of them can be omitted.

[0091] Considering that this invention uses a temperature-sensitive phase-change composite dielectric layer 2, an environmental temperature interference immunity test was conducted on the sample of Example 1 to examine the stability of the device within a common ambient temperature range. Figure 12 The following diagram shows the anti-interference test results of the dual-mode flexible capacitive sensor prepared in Embodiment 1 of the present invention under different ambient temperatures. Figure 12 As shown, under environments of 20℃, 30℃ and 40℃, although the baseline capacitance of the sample in Example 1 showed a certain degree of temperature dependence, the overall fluctuation range was controllable, and no baseline abrupt change or functional failure occurred, indicating that the sensor of the present invention has good output stability within the common ambient temperature range.

[0092] To verify the practical application capability in high-sensitivity mode, a weak pressure scenario application test was conducted on the slow-cooling configuration sample of Example 1. Figure 13 The following is a graph showing the output curve of the dual-mode flexible capacitive sensor prepared in Embodiment 1 of the present invention in a practical application test in high-sensitivity mode. The results are as follows: Figure 13 As shown. In high-sensitivity mode, the dual-modal flexible capacitive sensor can be attached to the human throat, pulse, or other weak pressure signal acquisition sites, maintaining good fit and flexibility. This meets the practical application requirements for weak mechanical stimulation detection scenarios. In high-sensitivity mode, the slow-cooling configuration sample in Example 1 can acquire clear and continuous vocal cord vibration waveforms, and the output signal has good periodicity and distinguishability, indicating that the present invention is suitable for applications such as the detection of weak physiological signals in high-sensitivity mode.

[0093] To verify the practical application capability under wide-range mode, the rapid cooling configuration sample of Example 1 was subjected to application tests under high-pressure scenarios. Figure 14 The following is a graph showing the output curve of the dual-mode flexible capacitive sensor prepared in Embodiment 1 of the present invention in a wide-range mode practical application test. The results are as follows: Figure 14 As shown, in wide-range mode, the dual-modal flexible capacitive sensor can be used in scenarios with relatively large pressure, such as finger pressing, grasping, and contact loading, while maintaining good structural integrity and signal output capability during actual operation. In wide-range mode, the sample output of the rapid-cooling configuration in Example 1 can form a distinguishable real-time response signal according to the changes in the intensity of multi-level pressing. The output amplitude corresponding to different pressure levels has good resolution, indicating that the present invention is suitable for detection needs with a large pressure range in wide-range mode.

[0094] In summary, this embodiment, by setting a temperature-sensitive phase-change composite dielectric layer 2 containing PCL, [EMIM][TFSI], MWCNTs, PEG-400, and SDBS between the upper electrode layer 1 and the lower electrode layer 3, and implementing thermal history elimination and differentiated cooling after device assembly, enables the same device to switch in situ between high-sensitivity mode and wide-range mode. Combined with... Figures 3-14The results shown further illustrate that the dual-mode flexible capacitive sensor based on phase change regulation described in this invention not only has reversible mode switching capability, but also has good dynamic performance, environmental adaptability and practical application potential.

[0095] In summary, this invention provides a dual-modal flexible capacitive sensor based on phase change modulation and its fabrication method. After device assembly, this invention eliminates the thermal history of the temperature-sensitive phase change composite dielectric layer 2 and performs controlled cooling. Utilizing the competition mechanism between the crystallization kinetics and thermodynamics of the semi-crystalline polymer at different cooling rates, it achieves physical reconstruction of the internal microstructure. This allows the same sensor to be configured in situ and reversibly between a high-sensitivity mode and a wide-range mode. This invention requires no hardware replacement, has a simple process, good repeatability, and application flexibility, showing broad application prospects in flexible wearable devices, human-computer interaction, and intelligent robots.

[0096] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A method for fabricating a dual-modal flexible capacitive sensor based on phase transition modulation, characterized in that, The method for fabricating a dual-modal flexible capacitive sensor based on phase transition modulation includes: S10, prepare a temperature-sensitive phase change composite dielectric layer film by pre-preparing a polymer solution and a conductive filler suspension, adding the conductive filler suspension to the polymer solution, then adding 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and polyethylene glycol, and mixing evenly to obtain a composite precursor solution; the composite precursor solution is formed into a film and dried to obtain a temperature-sensitive phase change composite dielectric layer film. S20, Obtain the upper and lower electrode layers of the dual-modal flexible capacitive sensor for later use; S30, the surfaces to be bonded, including the upper electrode layer, the lower electrode layer, and the temperature-sensitive phase change composite dielectric film, are subjected to plasma activation treatment; the temperature-sensitive phase change composite dielectric film is sandwiched between the upper electrode layer and the lower electrode layer, and hot-pressed bonded at a temperature below the melting point of polycaprolactone to encapsulate the edge of the device. S40, the assembled bimodal flexible capacitive sensor is heated to a temperature above the melting point of polycaprolactone and held at that temperature to eliminate thermal history; then the bimodal flexible capacitive sensor is subjected to controlled cooling at different cooling rates.

2. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 1, characterized in that: In step S10, when preparing the polymer solution, polycaprolactone is dissolved in dichloromethane to form a polymer solution. When preparing the conductive filler suspension, multi-walled carbon nanotubes and sodium dodecylbenzene sulfonate are taken and dispersed in dichloromethane to form a conductive filler suspension. The multi-walled carbon nanotubes and sodium dodecylbenzene sulfonate are ultrasonically dispersed and mixed.

3. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 2, characterized in that: In step S10, polycaprolactone is dissolved in dichloromethane to form a polymer solution with a dichloromethane mass fraction of 10%, thereby forming a PCL / DCM solution with a mass fraction of 10 wt%. 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt and polyethylene glycol are added to the polymer solution under a nitrogen protective atmosphere.

4. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 2, characterized in that: In step S10, when the composite precursor liquid is formed and dried, the composite precursor liquid is poured into a polytetrafluoroethylene mold, and after being allowed to stand at room temperature for volatilization and then vacuum dried, a temperature-sensitive phase change composite dielectric layer film is obtained.

5. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 1, characterized in that: Both the upper and lower electrode layers are flexible conductive electrode layers.

6. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 5, characterized in that: The flexible conductive electrode layer is made of copper foil, aluminum foil, or a flexible printed circuit board.

7. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 6, characterized in that: In step S30, when plasma activation treatment is performed on the surfaces to be bonded, including the upper electrode layer, the lower electrode layer, and the temperature-sensitive phase change composite dielectric layer film, the plasma activation treatment conditions are 100W for 30s, and the hot-press bonding conditions are 40℃, 1kPa, and 30min. When encapsulating the device edge, the device edge is encapsulated with silicone material and cured at room temperature for 24h.

8. The method for fabricating a dual-modal flexible capacitive sensor based on phase change modulation as described in claim 1, characterized in that: In step S40, when the assembled dual-mode flexible capacitive sensor is heated to a temperature higher than the melting point of polycaprolactone and held at that temperature, the thermal history elimination condition is to hold at 70°C for 15 minutes. When controlling the cooling of a dual-mode flexible capacitive sensor using different cooling rates, the cooling rates are divided into slow cooling rates and fast cooling rates. The dual-mode flexible capacitive sensor is configured as a high-sensitivity mode using a slow cooling rate, and as a wide-range mode using a fast cooling rate. The configuration conditions for the high-sensitivity mode are cooling to 25°C at a rate of 1.5°C / min, and the configuration conditions for the wide-range mode are cooling to 25°C at a rate of 12°C / min using air cooling.

9. A phase-change modulated dual-mode flexible capacitive sensor, fabricated using the method described in any one of claims 1-8, characterized in that: The phase-change-controlled dual-mode flexible capacitive sensor includes an upper electrode layer, a lower electrode layer, and a temperature-sensitive phase-change composite dielectric layer located between the upper electrode layer and the lower electrode layer.

10. The dual-modal flexible capacitive sensor based on phase change modulation as described in claim 9, characterized in that: The temperature-sensitive phase change composite dielectric layer comprises the following raw materials in parts by weight: 100 parts of polycaprolactone, 8 parts of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 0.6 parts of multi-walled carbon nanotubes, 6 parts of polyethylene glycol, and 0.12 parts of sodium dodecylbenzenesulfonate.

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