Preparation method of flexible array capacitive pressure sensor based on IPMC

Abstract

The invention discloses a preparation method of a flexible array capacitive pressure sensor based on IPMC, and relates to a flexible sensing technology. The sensor adopts a five-layer symmetrical composite structure and comprises a flexible PI packaging layer, a patterned copper electrode network and a Nafion-PEO nanofiber dielectric layer. A flexible PI base film is prepared through a spin-coating and sintering process, and a snakelike extension electrode is formed by combining a micro-nano mask and a magnetron sputtering technology; the preparation method comprises the following steps: directionally preparing a Nafion-PEO composite nanofiber dielectric membrane by adopting an electrostatic spinning technology, and activating a proton conduction channel through ion exchange; and multi-layer heterostructure integration is realized through vacuum thermocompression bonding. Through topological adaptation of the fiber reinforced composite dielectric layer and the array electrodes, the pressure sensitivity, mechanical flexibility and environmental adaptability of the sensor are improved, the problems that a traditional flexible sensor is low in ion migration efficiency, insufficient in spatial resolution and the like are solved, and the sensor can be widely applied to the fields of intelligent wearing, health monitoring and high-resolution detection of dynamic pressure fields.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible sensors, and specifically to a preparation method of a flexible array capacitive pressure sensor based on Ionic Polymer Metal Composite (IPMC), which is particularly suitable for high-resolution dynamic pressure detection in a curved surface fitting scenario. Background Art

[0002] With the development of technology, many researchers have carried out in-depth research on the application of sensors in fields such as interactive electronics, dynamic signal monitoring, and human-computer interaction. However, their limitations have become increasingly prominent. Most existing sensors adopt a rigid electrode structure, resulting in limited detection accuracy and response performance in a changing environment. In addition, the chemical stability and mechanical strength of traditional materials are insufficient, further restricting the practical application of sensors. To solve the above problems, there is an urgent need for a new type of sensor that can organically combine high sensitivity, fast response, and environmental adaptability, take into account mechanical flexibility and chemical selectivity, and provide chemical and biological detection in a complex environment. Summary of the Invention

[0003] The present invention aims to provide a flexible array capacitive pressure sensor based on IPMC and its preparation method. Through the innovative design of the dielectric material system and the optimization of the multi-layer stacked structure topology, the key technical problems existing in traditional flexible sensors, such as limited ion migration efficiency, insufficient mechanical compliance, and low spatial resolution, are effectively solved, thereby realizing high-resolution dynamic pressure detection.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a flexible array capacitive pressure sensor based on IPMC, which has a five-layer symmetric composite structure with excellent flexible characteristics and array detection functions. Specifically, from the outside to the inside, it includes:

[0006] Flexible outer encapsulation protection layer: It is composed of a flexible PI-based film, which provides mechanical protection and environmental isolation for the sensor, ensuring the stable operation of the sensor in a complex environment;

[0007] Patterning copper electrode layer: Integrated on the inner surface of the base film by micro-nano processing technology, it includes copper electrodes distributed in an array and serpentine extension leads for transmitting electrical signals; realizing the conversion of pressure-electrical signals;

[0008] Nanofiber dielectric layer: A Nafion nanofiber film prepared by electrospinning technology in a directional manner to achieve high-sensitivity pressure response of the sensor.

[0009] The fiber diameter of the nanofiber dielectric layer can be 100 - 500 nm, the porosity can be 60% - 80%, and the ion exchange capacity can be ≥ 0.8 meq / g.

[0010] The copper electrodes distributed in an array have a 3×3 circular topological structure. The copper electrodes are connected by serpentine leads. The thickness of the copper electrodes can be 50 - 200 nm, the line width of the serpentine extended leads can be ≤ 100 μm, and the center-to-center spacing of adjacent electrodes can be 2 - 5 mm.

[0011] The present invention provides a preparation method of a flexible array capacitive pressure sensor based on IPMC, comprising the following steps:

[0012] 1) Preparation of a flexible polyimide (PI) - based film: A PI prepolymer solution is spin - coated on the surface of an optical - grade silicon wafer substrate, and through a stepped heating and curing procedure, the orderly arrangement of molecular chains and the release of residual stress are achieved, and finally, the flexible PI - based film is peeled off.

[0013] 2) Preparation of a micro - nano - patterned mask plate: Based on a preset electrode array topological structure, electrode and extended lead via arrays are ablated on a metal sheet to prepare an electrode - patterned mask plate.

[0014] 3) Magnetron - sputtered patterned copper electrodes: The patterned mask plate and the PI - based film are aligned and laminated, and by using a high - power pulsed magnetron sputtering process, a copper conductive layer is deposited on the surface of the base film, and after mask - removing treatment, an array of copper electrodes with a serpentine extended structure and extended leads are formed.

[0015] 4) Functional preparation of a Nafion - PEO nanofiber dielectric film: Polyethylene oxide (PEO) and a Nafion solution are blended by mass ratio to form a Nafion - PEO solution, and an electrostatic spinning process is used to form a nanofiber network film, which is impregnated with an ionic solution to activate the proton - conduction function, and a functionalized nanofiber dielectric layer is obtained.

[0016] 5) Multilayer heterostructure integrated assembly: The functionalized Nafion nanofiber film is sandwiched between two groups of patterned copper electrode / PI - based film assemblies, and a five - layer symmetric structure packaging is completed through vacuum thermocompression bonding and ultrasonic wedge - welding processes.

[0017] In step 1), the stepped heating and curing procedure is: heating in a tube furnace, 80℃ / 1h → 150℃ / 2h → 250 - 300℃ / 1h, and peeling off after natural cooling.

[0018] In step 2), the arrayed copper electrodes have a 3×3 circular topological structure. The 3×1 circular arrays in each column are interconnected, and extended leads are formed below.

[0019] In step 3), the conditions of the high-power pulsed magnetron sputtering process can be: a magnetron sputtering power of 300 W and a sputtering time of 30 min.

[0020] In step 4), the mass ratio of the Nafion-PEO solution is 4:1, and the electrospinning parameters include: an injection speed of 150 μL / h, a voltage of 3 - 4 kV, a receiving distance of 12 mm, and a roller moving speed of 6 mm / min.

[0021] In step 4), the electrospinning forms a nanofiber network membrane, and the proton conduction function is activated by immersion in an ionic solution. Specifically, after mechanical stirring and vacuum degassing, an interconnected nanofiber network membrane is prepared using an electrospinning system. Subsequently, the fiber membrane is immersed in the ionic solution, and the proton conduction channels are activated through ion exchange, finally obtaining a functionalized nanofiber dielectric layer.

[0022] In step 4), the ionic solution can be an aqueous solution of LiCl, NaCl, or KCl, and the immersion time can be 2 - 4 h.

[0023] In step 5), the five-layer symmetric structure packaging is completed through vacuum thermocompression bonding and ultrasonic wedge bonding processes. Specifically, the interlayer microstructural conformal contact can be achieved through a precision alignment fixture, the interface fusion is realized using the vacuum thermocompression bonding process, and finally, a gold-plated copper lead with a diameter is bonded to the electrode port through the ultrasonic wedge bonding process to complete the integration of the flexible pressure sensor array with a five-layer symmetric stack structure.

[0024] In step 5), the conditions of the vacuum thermocompression bonding can be: a temperature of 80 - 100 °C, a pressure of 0.5 - 1 MPa, and a time of 10 - 15 min.

[0025] The innovative material selection and multi-layer structure design of the present invention not only achieve tight conformal contact at the electrode-dielectric layer interface, but also significantly improve the pressure response performance and environmental adaptability of the sensor through the IPMC fiber reinforcement effect, enabling it to exhibit performance advantages in complex curved surface fitting, multi-dimensional deformation adaptation, and higher-resolution pressure detection.

[0026] Compared with the prior art, the beneficial effects achieved by the technical solution of the present invention are as follows: First, through the collaborative design of the flexible substrate and the composite dielectric material, while ensuring excellent mechanical flexibility, the charge transfer efficiency is significantly improved. Second, by adopting the topological adaptation process of the array-patterned electrode and the dielectric layer, the sensor has high-sensitivity pressure response and high-resolution precise signal capture capabilities. This technology effectively solves the inherent defects of flexible sensors such as signal distortion and mechanical fatigue under complex working conditions, and provides a reliable solution for the high-resolution detection and precise quantitative analysis of dynamic pressure fields. A fiber membrane based on a Nafion flexible dielectric layer with good proton conductivity, ion exchange capacity, and water absorption rate. This sensor realizes the precise conversion of pressure-electric signals through the capacitance change caused by deformation. This sensor can be widely applied in fields such as environmental monitoring, health detection, intelligent wearable devices, and energy harvesting. Description of the Drawings

[0027] Figure 1 It is a schematic flow chart of the preparation method of the present invention;

[0028] Figure 2 It is a schematic diagram of the product of the present invention. Detailed Embodiments

[0029] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present invention clearer, the following further describes the present invention in detail with reference to the drawings and embodiments.

[0030] See Figure 1 , the present invention provides a preparation method of a flexible arrayed capacitive pressure sensor based on IPMC, including the preparation of a PI protective layer, the preparation of a copper electrode, and the preparation of an electrospinning solution. The solution is electrospun into a nanofiber thin film as the core dielectric layer by an electrospinning machine, and finally a sensor is made through assembly.

[0031] The specific technical solutions adopted are as follows:

[0032] The first step is to configure the PI solution: Use an electronic balance to weigh 4 g of polyimide precursor solution and 1 g of N,N-dimethylacetamide solution (DMAC) respectively, mix the two and place them in a glass bottle; put magnetic particles into the mixed solution and place it on a magnetic particle stirrer, set the rotation speed to 150 rpm, and perform mechanical stirring to fully mix the PI precursor solution and the DMAC solution. After mixing, keep the prepared solution for later use.

[0033] Step 2: Prepare the PI encapsulation base film: Place the optical-grade silicon wafer substrate on the spin coater tray, turn on the vacuum pump to evacuate air and adsorb the silicon wafer substrate; pour the prepared PI solution onto the silicon wafer substrate, set the rotation speed of the spin coater to 1500 rpm, set the time to 60 s, and turn on the spin coater to evenly cover the PI solution on the silicon wafer substrate; place the silicon wafer covered with the uniform PI solution in a box furnace for heating, heat to 300 °C, keep warm for 60 min, and then naturally cool to room temperature. Peel the formed PI base film from the silicon wafer to complete the preparation of the PI encapsulation base film.

[0034] Step 3: Prepare the patterned copper electrodes: Design and manufacture a metal mask plate using the high-power pulsed magnetron sputtering process according to the layout position of the copper electrodes. The shape of the metal mask plate is a 3×3 circular array, and the 3×1 circular arrays in each column are interconnected and form extended leads below. Align and bond the mask plate with the PI base film, and place it in the magnetron sputtering machine to prepare the copper electrodes; the target material of the magnetron sputtering machine is a copper target, set the sputtering power to 300 W, and set the sputtering time to 30 min; after sputtering, take out the PI base film and the mask plate, and remove the mask plate to complete the preparation of the copper electrodes.

[0035] Step 4: Prepare the electrospinning solution of the Nafion-PEO nanofiber dielectric film: Weigh 16 mg of PEO solid powder and 4 g of Nafion membrane solution respectively using a precision electronic balance and place them in a plastic volumetric bottle; at the same time, measure 1.7 mL of deionized water and absolute ethanol and pour them into the plastic bottle to mix and form a Nafion solution. Finally, place the mixed Nafion solution on a magnetic particle stirrer, set the rotation speed to 150 rpm, and stir mechanically to fully mix the PEO and Nafion molecules. After mixing, keep the prepared solution for use; among them, the PEO solid powder uses the ultra-high molecular weight type (5 million) to reduce its influence on the performance of the Nafion fiber membrane as an impurity.

[0036] Fifth step, preparation of Nafion-PEO nanofiber dielectric film: Using an electrospinning device equipped with a DC high-voltage power supply, first suck 2 mL of Nafion solution into a 2.5 mL standard syringe, then assemble a disposable dispensing needle with an inner diameter of 0.1 mm, install it on a precision micro-injection pump and lock it. Set the liquid supply speed of the injection pump to 150 μL / h and the working liquid supply volume to be constantly 2 mL. Subsequently, start the DC high-voltage power supply. After grounding the ground wire end, connect it to the conductive layer of the roller evenly wrapped with non-creased aluminum foil paper on the surface, and connect the output end to the dispensing needle. Adjust the output voltage to the range of 3 kV - 4 kV until the fibers are stably spun out. Synchronously start the moving platform to reciprocate at a speed of 6 mm / min along a 12 mm spacing, so that the fibers are orderly deposited on the surface of the roller. After the electrospinning is completed, cut the obtained nanofiber membrane according to the required size, immerse it in an ionic solution for sufficient infiltration treatment, and finally prepare a functionalized Nafion-PEO nanofiber dielectric film.

[0037] Sixth step, integrated assembly of the sensor multi-layer heterostructure: Place the PI film with copper electrodes prepared on a flat surface, and accurately place the nanofiber membrane at the appropriate position on the PI base film through a fixture and a three-axis moving positioning system. Then, laminate another PI film with copper electrodes prepared on it to the bottom imide film through a fixture and a three-axis moving positioning system, and use a vacuum thermal compression bonding process to achieve interface fusion, so that the PI base film with copper electrodes and the nanofiber membrane are tightly combined into a whole. Finally, bond gold-plated copper leads with a diameter at the electrode ports through an ultrasonic wedge bonding process to complete the integration of a flexible pressure sensor array with a five-layer symmetric stack structure.

[0038] The present invention adopts a capacitive sensor structure, and a sensor is made by pressing array metal electrodes on both sides of a nanofiber film.

[0039] See Figure 2 , the flexible array capacitive pressure sensor based on IPMC has a five-layer symmetric composite structure, which from top to bottom is:

[0040] Flexible PI upper encapsulation layer, which is used to protect the internal structure of the sensor and provide flexible support;

[0041] Patterned copper upper electrode layer, which is integrated on the inner surface of the flexible PI upper encapsulation layer by micro-nano processing technology and is used to transmit electrical signals;

[0042] Nafion - PEO nanofiber dielectric layer, which is prepared directionally by electrospinning technology and is used as the core dielectric component for realizing pressure - electrical signal conversion;

[0043] Patterned copper lower electrode layer, which is integrated on the outer surface of the flexible PI lower encapsulation layer by micro-nano processing technology and cooperates with the patterned copper upper electrode layer to transmit electrical signals;

[0044] The flexible PI bottom encapsulation layer is used to protect the internal structure of the sensor and provide flexible support.

[0045] The fiber diameter of the Nafion - PEO nanofiber dielectric layer is 100 - 500 nm, the porosity is 60% - 80%, and the ion exchange capacity is 0.9 - 1.1 meq / g.

[0046] The copper electrode thickness of the patterned copper upper electrode layer and the patterned copper lower electrode layer is 50 - 200 nm.

[0047] The thickness of the upper and lower flexible PI encapsulation layers can both be 50 - 100 μm, and the surface roughness Ra < 0.1 μm;

[0048] The copper electrode array can be in a 3×3 circular topology structure, and the electrodes are connected by serpentine leads.

[0049] The line width of the serpentine lead ≤ 100μm, and the center distance between adjacent electrodes is 2 - 5 mm.

[0050] The present invention integrates the composition formulation and structure preparation technologies of the Nafion - PEO nanofiber dielectric film, improves the proton conductivity, ion exchange capacity and water absorption rate of the film, and has a certain flexibility. Through the collaborative composite design of the PI film with copper electrodes and the nanofiber film dielectric material, while ensuring excellent mechanical flexibility, the charge transfer efficiency is significantly improved, enhancing the environmental adaptability of the sensor and improving the output performance; adopting the topological adaptation process of the array patterned electrodes and the dielectric layer, the sensor has high - sensitive pressure response and high - resolution precise signal capture capabilities, providing a reliable solution for the high - resolution detection and precise quantitative analysis of the dynamic pressure field, and having important practical production application significance.

[0051] The above - mentioned embodiments are only preferred embodiments of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention shall still fall within the scope covered by the patent of the present invention.

Claims

1. A flexible array capacitive pressure sensor based on IPMC, characterized in that Specifically from outside to inside, it includes: Flexible outer encapsulation protection layer: It is composed of a flexible PI-based film, providing mechanical protection and environmental isolation for the sensor to ensure the stable operation of the sensor in a complex environment; Patterned copper electrode layer: Integrated on the inner surface of the base film by micro-nano processing technology, including copper electrodes distributed in an array and serpentine extension leads, used for transmitting electrical signals; realizing the conversion of pressure-electric signals; Nanofiber dielectric layer: A Nafion nanofiber thin film prepared by electrospinning technology to achieve a high-sensitivity pressure response of the sensor.

2. The flexible array capacitive pressure sensor based on IPMC according to claim 1, wherein The fiber diameter of the nanofiber dielectric layer is 100 - 500 nm, the porosity is 60% - 80%, and the ion exchange capacity is ≥0.8 meq / g.

3. The flexible array capacitive pressure sensor based on IPMC according to claim 1, characterized in that The copper electrodes distributed in an array have a 3×3 circular topological structure, and the copper electrodes are connected by serpentine leads. The thickness of the copper electrodes is 50 - 200 nm, the line width of the serpentine extension leads is ≤100 μm, and the center distance between adjacent electrodes is 2 - 5 mm.

4. A preparation method of a flexible array capacitive pressure sensor based on IPMC, characterized in that It includes the following steps: 1) Preparation of flexible PI-based film: Spin-coat a PI prepolymer solution on the surface of an optical-grade silicon wafer substrate, and through a stepped heating and curing process, achieve the ordered arrangement of molecular chains and the release of residual stress, and finally peel off to obtain a flexible PI-based film; 2) Preparation of micro-nano patterned mask plate: Based on a preset electrode array topological structure, ablate through holes for electrodes and extension leads on a metal sheet to prepare an electrode-patterned mask plate; 3) Magnetron sputtering patterned copper electrodes: Align and bond the patterned mask plate with the PI-based film, and use a high-power pulsed magnetron sputtering process to deposit a copper conductive layer on the surface of the base film, and form an array of copper electrodes and extension leads with a serpentine extension structure after removing the mask; 4) Functional preparation of Nafion-PEO nanofiber dielectric film: Blend polyethylene oxide and Nafion solution according to a mass ratio to form a Nafion-PEO solution, electrospin to form a nanofiber network film, and activate the proton conduction function through immersion in an ionic solution to obtain a functionalized nanofiber dielectric layer; 5) Multilayer heterostructure integrated assembly: Sandwich the functionalized Nafion nanofiber film between two groups of patterned copper electrode / PI-based film assemblies, and complete the five-layer symmetric structure encapsulation through vacuum hot pressing bonding and ultrasonic wedge welding processes.

5. The preparation method of a flexible array capacitive pressure sensor based on IPMC according to claim 4, characterized in that In step 1), the stepped heating and curing process is: Heat in a tube furnace, 80°C / 1h → 150°C / 2h → 250 - 300°C / 1h, and peel off after natural cooling.

6. The preparation method of a flexible array capacitive pressure sensor based on IPMC according to claim 4, characterized in that In step 2), the arrayed copper electrodes have a 3×3 circular topological structure, and the 3×1 circular arrays in each column are interconnected and form extension leads below.

7. The preparation method of a flexible array capacitive pressure sensor based on IPMC according to claim 4, characterized in that In step 3), the conditions of the high-power pulsed magnetron sputtering process are: magnetron sputtering power 300 W, sputtering time 30 min.

8. The preparation method of a flexible array capacitive pressure sensor based on IPMC according to claim 4, characterized in that In step 4), the mass ratio of the Nafion-PEO solution is 4:1; the electrospinning parameters include: injection speed 150 μL / h, voltage 3 - 4 kV, receiving distance 12 mm, and drum moving speed 6 mm / min.

9. The preparation method of a flexible array capacitive pressure sensor based on IPMC according to claim 4, characterized in that In step 4), the ionic solution is an aqueous solution of LiCl, NaCl or KCl, and the impregnation time is 2 to 4 h.

10. The preparation method of a flexible array capacitive pressure sensor based on IPMC according to claim 4, characterized in that In step 5), the conditions for the vacuum hot pressing bonding are: temperature 80 to 100 °C, pressure 0.5 to 1 MPa, and time 10 to 15 min.

Images