Wireless transmission type ionizing pressure sensor based on no liquid leakage and preparation method and application of wireless transmission type ionizing pressure sensor

Abstract

The invention provides a wireless transmission type ionizing pressure sensor based on no liquid leakage and a preparation method and application thereof. Aiming at the technical bottlenecks of electrolyte leakage, signal drifting, range limitation and the like of a traditional ionizing sensor, an in-situ polymerization type polyion liquid film is used as an active layer, and a monomer containing 1-vinyl-3-butylimidazole cations and diethylene glycol divinyl ether are cured to form a three-dimensional network structure; the main chain anchoring effect of cations is achieved, and signal drift caused by ion migration is eliminated. Moreover, the capacitor-inductor integrated assembly is innovatively constructed, and the capacitor unit adopts the composite layered electrode configuration, so that the effective contact area is increased, and the frequency test range is improved. The ionizing pressure sensor is designed to be of a wireless sensing structure, so that the ionizing pressure sensor has good expandability and environmental adaptability, signals are collected and processed in a wireless data transmission mode, the sensor can be applied to biological pressure testing, and accurate signal feedback is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible pressure sensing, and particularly relates to a wireless transmission type non-contact pressure sensor based on no liquid leakage, and a preparation method and application thereof. Background Art

[0002] In current flexible wireless sensing systems, although passive devices based on the inductance-capacitance (LC) resonance principle have been commercially applied in fields such as logistics tracking, their pressure sensing performance has significant bottlenecks, specifically including: traditional LC sensors mostly adopt interdigital capacitors, and their effective electrode contact area is usually 1-2 orders of magnitude lower than that of the stacked architecture, resulting in a generally small capacitance change rate ΔC / C0 less than 0.2 kPa-1, with relatively low sensitivity, and the actual pressure detection range is also greatly limited, usually limited to the range of 0-50 kPa.

[0003] In the field of non-contact capacitive sensing, existing technologies mostly use ionic gels as the sensing functional layer. Although the sensitivity can be increased to 1-500 kPa-1 by greatly increasing the capacitance density through the electric double layer capacitance (CEDL) effect of ions, due to the free state of anions and cations between polymer chains and the instability of the physical cross-linking network, the problem of ionic liquid leakage will occur under continuous pressure load. The continuous seepage of ionic liquid onto the sensing electrode causes the baseline signal drift of the sensor to be as high as 10-60% h-1, thus resulting in inaccurate pressure measurement. In addition, compared with the sandwich structure, the signal sensitivity of the non-contact capacitive sensor with an interdigital structure also has a relatively large difference. This is because the interface contact area between the ionic gel and the electrode in the interdigital structure is limited by the two-dimensional planar structure. Even with microstructural surface modification, its effective contact area is still less than 1 / 50 of the three-layer stacked architecture (typical value: planar electrode 0.05 mm 2 / mm 3 vs. sandwich structure 3.2 mm 2 / mm 3 ), seriously restricting the improvement of the signal amplitude.

[0004] With the rise of wearable devices and the increasing demand for portability, wireless sensing is very important in daily life. The importance of wireless sensing lies in that it breaks through the limitation of wired connection, making data acquisition more flexible, efficient and extensive.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] Aiming at the defects of the prior art, the present invention innovatively proposes a sandwich-type non-contact pressure sensor based on no liquid leakage and wireless transmission, and a preparation method and application thereof.

[0007] In terms of the process method, in the present invention, through the design of sensor functional materials, especially the molecular structure design, free ions are bound on the molecular chains, enhancing the stability of the cross-linked network and fundamentally eliminating the problem of ionic liquid leakage. Then, a polyionic liquid active sensing layer is obtained by curing the precursor. Finally, the interface bonding treatment is carried out using a plasma cleaner to achieve a sandwich stack full encapsulation integrating capacitance and inductance.

[0008] The prepared wireless transmission type ion-off pressure sensor can achieve a baseline drift rate of <0.5% h -1 for long-term stable monitoring, greatly improving the detection accuracy and stability. Moreover, the contact area density of the sandwich structure can reach 4 mm 2 / mm 3 , which is two orders of magnitude higher than that of interdigital capacitors, enabling the capacitance change rate ΔC / C0 to break through to 7 kPa -1 , effectively improving the sensitivity of the sensor.

[0009] To achieve the above object, the present invention provides a preparation method of a wireless transmission type ion-off pressure sensor based on no liquid leakage, including the following steps:

[0010] Prepare a polyionic liquid film without liquid leakage: Mix a monomer containing 1-vinyl-3-butylimidazolium cation, diethylene glycol divinyl ether and an initiator in a certain mass ratio to form a homogeneous precursor; Cure and polymerize the precursor to obtain a polyionic liquid film;

[0011] Process a flexible electrode: Laser cut a polyimide-copper substrate to prepare coil-electrode materials;

[0012] Assemble the sensor:

[0013] (1) After plasma activation treatment of the polyimide surfaces of the encapsulation layer and the flexible electrode, perform thermocompression bonding;

[0014] (2) Fix the polyionic liquid film at the center position of the coil of the flexible electrode, fold it along the center line so that the two coils of the flexible electrode are aligned and overlapped to form a sensor unit with a sandwich layer structure of electrode-polyionic liquid active layer-electrode;

[0015] (3) Thermocompress the overall sensor unit again to achieve complete encapsulation of the device, thus obtaining it.

[0016] In a preferred embodiment, in the step of preparing the polyionic liquid film without liquid leakage, in the monomer containing 1-vinyl-3-butylimidazolium cation, the anions include BF4 - , N(CF3SO2)2 - , Br - , PF6- 、 NO3 - at least one of them.

[0017] In a preferred embodiment, in the step of preparing a liquid - leakage - free polyionic liquid film, the mass ratio of the monomer containing 1 - vinyl - 3 - butylimidazolium cation to diethylene glycol divinyl ether is 50:(3 - 9).

[0018] In a preferred embodiment, in the step of preparing a liquid - leakage - free polyionic liquid film, the mixing can be carried out by conventional methods mastered by those skilled in the art, such as stirring with a magnetic stirrer at a speed of 450±50 rpm for 1 - 5 minutes.

[0019] In a preferred embodiment, in the step of preparing a liquid - leakage - free polyionic liquid film, the curing polymerization includes thermal curing and / or photocuring; preferably, the photocuring conditions include: using an ultraviolet light source with a wavelength of 360 - 370 nm, and curing for 1 - 2 hours under an irradiation intensity of 10 - 30 mW / cm 2 2.

[0020] In a preferred embodiment, in the step of preparing a liquid - leakage - free polyionic liquid film, during photocuring, the initiator includes ethyl 2,4,6 - trimethylbenzoyl - phenylphosphinate (TPOL); preferably, the mass of the initiator is 0.5 - 1% of the total mass of the monomer containing 1 - vinyl - 3 - butylimidazolium cation and diethylene glycol divinyl ether.

[0021] In a preferred embodiment, in the step of preparing a liquid - leakage - free polyionic liquid film, to obtain a polyionic liquid film with a specific thickness, the homogeneous precursor solution can be poured onto a silica gel template, and the film thickness can be controlled by PDMS spacer gaskets arranged on both sides. Subsequently, a glass sheet with a release film is covered to form a sealed structure, thereby realizing the curing conditions of water - proof and oxygen - proof. Preferably, the surface of the PDMS spacer gasket has a sandpaper microstructure with 10000 meshes, and the PDMS spacer gasket with the sandpaper microstructure is prepared by the following method: pouring the silica gel precursor liquid onto the surface of commercial sandpaper, and obtaining the PDMS spacer gasket with the sandpaper microstructure after demolding. In the present invention, by preparing a polyionic liquid film with a sandpaper microstructure, the sensitivity of the device can be effectively improved, especially under gradient pressure, making the sensor have higher resolution.

[0022] In a preferred embodiment, in the step of preparing a liquid - leakage - free polyionic liquid film, the thickness of the prepared polyionic liquid film is 50 - 200 μm.

[0023] In a preferred embodiment, in the step of processing the flexible electrode, the laser cutting conditions include: a cutting power of 20 - 40 W, a laser scanning speed of 100 - 140 mm / s, and the number of cutting passes is 8 - 10 times.

[0024] In a preferred embodiment, in the step of processing the flexible electrode, the prepared coil - electrode material has a left - right symmetric structure along the center - line position. The circular electrode on one side is located at the center of the coil. The electrode diameter is 1 - 3 mm, the coil diameter is 3 - 6 mm, the number of coil turns is 3 - 7 turns, and the wire width is 100 - 200 μm. Preferably, the number of coil turns is 3.5, 4, 6, 7 turns, and the wire widths correspond to 200, 180, 130, 100 μm respectively.

[0025] In a preferred embodiment, in the step of assembling the sensor, in step (1), the encapsulation layer is polydimethylsiloxane (PDMS).

[0026] In a preferred embodiment, in the step of assembling the sensor, the thermocompression bonding conditions in step (1) include: a treatment power of 30 - 50 W, a treatment time of 0.5 - 2 min. After bonding, the device is placed in an oven, the drying temperature is 65 - 75 °C, and the drying time is 10 - 30 min.

[0027] In a preferred embodiment, for the prepared wireless - transmission type non - contact pressure sensor, after sequentially assembling the encapsulation layer, the circular electrode and the spiral coil, and the poly - ionic liquid film, the encapsulation layer is then folded and bonded to form an integrated structure.

[0028] In a preferred embodiment, for the prepared wireless - transmission type non - contact pressure sensor, under a constant external force of 400 kPa, the noise level within 10 min is 0.3 MHz, the drift ratio is only 1%, and there is no liquid leakage phenomenon in the poly - ionic liquid material.

[0029] Another object of the present invention is a wireless - transmission type non - contact pressure sensor prepared by the method described in any one of the above, based on no liquid leakage.

[0030] Another object of the present invention is the application of the wireless - transmission type non - contact pressure sensor prepared by the method described in any one of the above, based on no liquid leakage, in human - machine interaction, health monitoring, electronic skin, and portable intelligent wearable devices.

[0031] In a preferred embodiment, the application method includes: connecting a network analyzer to the prepared wireless transmission type off-electric pressure sensor. When an external load acts on the off-electric sensor device, the capacitance value increases, causing a resonance frequency shift. By monitoring the change relationship of the coil frequency, the mechanical signal quantification can be achieved. The sensitivity of the wireless device is extended to 1.5 MHz kPa-1, and it can be applied to high-precision mechanical tests for a long time.

[0032] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0033] 1. The present invention realizes a performance breakthrough of the off-electric sensing functional material, solves the problem of ionic liquid leakage of traditional ion gels under long-term large pressure. Moreover, the conductivity of the prepared polyionic liquid film (10 -6 S / cm) is 2-4 orders of magnitude higher than that of ordinary dielectric elastomers (PDMS, 10 -10 S / cm), greatly improving the sensitivity. In addition, the modulus of the polyionic liquid film can be adjusted by adding different proportions of diethylene glycol divinyl ether. For example, when adding 6%, 12%, and 18% of diethylene glycol divinyl ether by the mass of the monomer, and other conditions remain unchanged, their moduli are 31, 13, and 0.8 MPa respectively, enabling it to be applied in different scenarios, such as robot movement (MPa level), pulse test (kPa level), etc. The polyionic liquid material adopted in the present invention has a low adhesion energy with the electrode, minimizing the energy loss of contact and de-adhesion of the prepared off-electric pressure sensor under high-frequency movement, thereby improving the accuracy of the sensor in the time domain and frequency domain.

[0034] 2. The present invention realizes wireless wide-range pressure testing. The existing off-electric pressure sensors collect their capacitance values through an LCR, establish the correlation between pressure and capacitance signals, and then achieve the acquisition of mechanical sensing data. This method is a conventional practice in the prior art, focusing on measuring the change of capacitance value with pressure. In the present invention, however, by using a network analyzer to monitor and analyze the coil frequency, the quantification of mechanical signals can be achieved, which is essentially different from the traditional principle of collecting capacitance values through an LCR. Moreover, due to the large capacitance change range of the off-electric sensor device of the present invention, the resonance frequency (f r ) change range is expanded. For example, in the pressure range of 100 kPa, the f r change range is compared with the initial resonance frequency (f r0) It can reach 6-28%, while that of ordinary dielectric elastomers is only 0.5-2%. Moreover, the wireless capacitive sensor based on this polyionic liquid film has a wide working range. For pressure testing, the polyionic material can detect signals above 100 kPa, while for ordinary dielectric elastomers, the pressure reaches 60 kPa and it is already saturated. Therefore, the present invention is applicable to activity monitoring in a wider pressure range.

[0035] 3. The flexible wireless non-ion-leaking ionic pressure sensor of the present invention has a wide range while also taking into account high sensitivity. Especially in the range of 0-20 kPa, the sensitivity can reach -1.5 MHz / kPa -1 and in the pressure range of 20-200 kPa, the sensitivity is -0.05 MHz / kPa -1 .

[0036] 4. Through the design of the superimposed sandwich device structure and the highly stable polyionic liquid material of the present invention, the device shows extremely high signal stability during constant pressure testing, and the quality factor reaches 74. The higher the quality factor, the sharper the echo loss trough, and the smaller the swing range of the f r signal at the trough and the smaller the signal noise. The wireless non-ion-leaking ionic pressure sensor prepared by the present invention has a high signal-to-noise ratio and is especially suitable for the fields of small pressure measurement and high-precision mechanical testing.

[0037] 5. By designing the molecular structure of the material, the present invention fixes the cation on the molecular chain to prevent signal drift caused by ion liquid leakage under large pressure. The prepared sensor has a stable f r signal during constant pressure testing at a large pressure. The drift ratio is only 1% after 10 minutes, and the subsequent signals remain stable all the time, and the signal-to-noise ratio reaches 43 dB.

[0038] 6. The non-ion-leaking wireless ionic pressure sensor prepared by the present invention can be widely applied in multiple fields due to its excellent performance. In medical and health, it can be used for implantable detection of bone / tooth stress (0.5-300 kPa), gait analysis (response time 50 ms), and mechanical monitoring of medical rehabilitation training; in the industrial end, it can be adapted to flexible robot tactile sensing (0.5-500 kPa detection), and at the same time support wireless frequency signal transmission and fatigue pressure cycle tests of tens of thousands of times, meeting the long-term stable requirements of the medical-industrial dual scenarios.

[0039] In summary, the wireless transmission non-ion-leaking ionic pressure sensor of the present invention innovatively integrates the polyionic liquid film material system and the sandwich layer structure design, overcoming the core technical bottlenecks of traditional ionic pressure sensors such as limited high-pressure detection range, baseline drift, and too low signal-to-noise ratio.

[0040] In addition, in the present invention, a traditional wired capacitive sensor is made wireless by monitoring the coil frequency through a network analyzer. When an external load acts on the electrified sensor device, the capacitance value increases, causing a resonance frequency shift. By monitoring the change relationship of the frequency, mechanical signals are quantified, breaking through the limitation of wired connection and making data acquisition more flexible, efficient, and extensive.

[0041] In scenarios such as mechanical monitoring of biomedical implants (such as dynamic analysis of bone stress) and tactile feedback of industrial robots, accurate pressure sensing without liquid leakage and wireless operation under a wide range of pressures has been successfully achieved. Its technical indicators and long-term stability are significantly superior to similar products, providing an innovative solution for accurate medical diagnosis and intelligent equipment perception, and having clear industrialization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] From the following detailed description of the embodiments of the present invention in conjunction with the drawings, these and / or other aspects and advantages of the present invention will become clearer and easier to understand, where:

[0043] Figure 1 It is a schematic structural diagram and reaction mechanism diagram of the electrified pressure sensor based on wireless transmission without liquid leakage of the present invention.

[0044] Figure 2 It is a schematic structural formula diagram of the polyionic liquid reaction monomer and diethylene glycol divinyl ether of the electrified pressure sensor based on wireless transmission without liquid leakage of the present invention.

[0045] Figure 3 It is a schematic diagram of the polyionic liquid reaction process of the electrified pressure sensor based on wireless transmission without liquid leakage of the present invention.

[0046] Figure 4 It is a schematic diagram of electrode coil cutting of the electrified pressure sensor based on wireless transmission without liquid leakage according to an embodiment of the present invention.

[0047] Figure 5 It is a graph showing the change of the resonance frequency of a leak-free wireless electrified pressure sensor according to Embodiment 1 of the present invention with pressure.

[0048] Figure 6 It is a graph showing the change of the return loss of a leak-free wireless electrified pressure sensor according to Embodiment 1 of the present invention with frequency.

[0049] Figure 7 It is a graph showing the change of the resonance frequency of a wireless pressure sensor with pressure in the preparation method of a leak-free wireless electrified pressure sensor according to Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0051] Unless otherwise specified, the technical means used in the present invention are conventional means well known to those skilled in the art. All kinds of raw materials, reagents, instruments and equipment used in the present invention can be obtained through the market or can be prepared by existing methods. The reagents used in the present invention are of analytical purity unless otherwise specified.

[0052] Example 1

[0053] A preparation method of a wireless transmission type off-electrode pressure sensor based on no liquid leakage, see Figures 1-3 , specifically including the following steps:

[0054] (1) Preparation of a polyionic liquid film without liquid leakage:

[0055] S1 Mix 1-vinyl-3-butylimidazolium tetrafluoroborate and diethylene glycol divinyl ether in a mass ratio of 50:3, and then obtain a basic mixed precursor liquid after magnetic stirring for 2 minutes.

[0056] S2 Add 0.5% of the photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphinate (TPOL) based on the mass of the mixed liquid to the mixed precursor liquid, and stir for 2 minutes at a speed of 450 rpm by a magnetic stirrer to obtain a homogeneous precursor solution.

[0057] S3 Assembly of the film-forming device: Under a nitrogen environment, quantitatively pour the homogeneous precursor solution onto a silicone template, control the film thickness and the microstructure on the film surface through PDMS spacer gaskets with a 100 μm spacing distance on both sides and a microstructure of 10,000-mesh sandpaper, and then cover a glass sheet with a release film to form a sealed structure to achieve a curing condition of water and oxygen isolation.

[0058] S4 Photo-curing polymerization to form a film: Use an ultraviolet light source with a wavelength of 365 nm to cure for 1 hour under an irradiation intensity of 30 mW / cm 2 . Peel the cured film from the silicone sheet, and finally obtain a polyionic liquid film with a thickness of 100 μm and a microstructure of 10,000-mesh sandpaper on the surface. After a tensile test, its modulus is calculated to be 31 MPa.

[0059] (2) Processing of a flexible electrode: Process a polyimide-copper substrate by laser cutting, set the cutting power to 30 W, the scanning speed of the laser to 100 mm / s, and the number of cutting times to 10 times to prepare a left-right symmetric coil and electrode. The diameter of the unilateral circular electrode is 2 mm, the number of turns of the coil is 4 turns, and the line width is 180 μm. The specific morphology is asFigure 4 As shown in the lower left middle figure.

[0060] (III) Assembling the sensor:

[0061] (1) After plasma activation treatment of the surface of the polydimethylsiloxane encapsulation layer (PDMS) and the polyimide surface of the polyimide - copper electrode by a plasma cleaner, bonding is carried out. Set the power to 40W and the time to 1min; place the bonded device in an oven, set the temperature to 70°C, and take it out after 20min.

[0062] (2) Fix the polyionic liquid film at the center position of the coil of the flexible electrode, and fold it along the center line ( Figure 4 as shown by the red - marked line in the figure) so that the two coils are aligned and overlapped, forming a sensor unit with a sandwich - layer structure of electrode - polyionic liquid active layer - electrode.

[0063] (3) Thermally press the whole sensor unit again to achieve complete encapsulation of the device, thus obtaining the product.

[0064] Example 2

[0065] A preparation method of a wireless - transmission - type ion - off pressure sensor based on no liquid leakage, see Figures 1-3 , which specifically includes the following steps:

[0066] (I) Preparing a polyionic liquid film with no liquid leakage:

[0067] S1 Mix 1 - vinyl - 3 - butylimidazolium tetrafluoroborate and diethylene glycol divinyl ether in a mass ratio of 25:3, and then obtain a basic mixed precursor liquid after magnetic stirring for 2 minutes.

[0068] S2 Add 2,4,6 - trimethylbenzoyl - diphenylphosphinic acid ethyl ester (TPOL), which is 0.5% of the mass of the mixed liquid, to the mixed precursor liquid, and stir it with a magnetic stirrer at a speed of 450rpm for 2 minutes to obtain a homogeneous precursor solution.

[0069] S3 Assembly of the film - forming device: Under a nitrogen environment, quantitatively pour the homogeneous precursor solution onto a silica gel template, control the film thickness and the microstructure of the film surface through a PDMS spacer with a 100μm interval distance on both sides and a microstructure of 10000 - mesh sandpaper, and then cover a glass sheet with a release film to form a sealed structure to achieve the curing conditions of water - proof and oxygen - proof.

[0070] S4 Photo - curing polymerization to form a film: Use an ultraviolet light source with a wavelength of 365nm, at 30mW / cm 2Cure for 1 hour under irradiation intensity, peel the cured film from the silicone sheet, and finally obtain a polyionic liquid film with a thickness of 100 μm. After tensile testing, its modulus is calculated to be 13 MPa.

[0071] (2) Processing flexible electrodes: Process the polyimide-copper substrate by laser cutting. Set the cutting power to 30 W, the laser scanning speed to 100 mm / s, and the number of cutting times to 10 times to prepare symmetric coils and electrodes on the left and right. The diameter of the unilateral circular electrode is 2 mm, the number of coil turns is 4, and the line width is 180 μm. The specific morphology is as shown in Figure 4 the lower left figure in the middle.

[0072] (3) Assembling the sensor:

[0073] (1) Plasma activate the surface of the polydimethylsiloxane encapsulation layer (PDMS) and the polyimide of the polyimide-copper electrode through a plasma cleaner and then bond them. Set the power to 40 W and the time to 1 min; Place the bonded device in an oven, set the temperature to 70 °C, and take it out after 20 min.

[0074] (2) Fix the polyionic liquid film at the center position of the coil of the flexible electrode and fold it along the center line ( Figure 4 the red line marked in the figure) so that the two coils are aligned and overlapped to form a sensor unit with a sandwich-like structure of electrode-polyionic liquid active layer-electrode.

[0075] (3) Thermally press the overall sensor unit again to achieve complete encapsulation of the device, thus obtaining the product.

[0076] Example 3

[0077] A preparation method of a wireless transmission type ionoelectric pressure sensor based on no liquid leakage, see Figures 1-3 , specifically including the following steps:

[0078] (1) Preparing a polyionic liquid film without liquid leakage:

[0079] S1 Mix 1-vinyl-3-butylimidazolium tetrafluoroborate and diethylene glycol divinyl ether in a mass ratio of 50:9, and then obtain a basic mixed precursor solution after magnetic stirring for 2 minutes.

[0080] S2 Add ethyl 2,4,6-trimethylbenzoylphosphinate (TPOL), which is 0.5% of the mass of the mixed solution, to the mixed precursor solution, and stir it for 2 minutes at a speed of 450 rpm through a magnetic stirrer to obtain a homogeneous precursor solution.

[0081] S3 Film Coating Device Assembly: In a nitrogen environment, a homogeneous precursor solution is quantitatively poured onto a silica gel template. The film thickness and the microstructure on the film surface are controlled by PDMS spacer gaskets with a 100-μm spacing distance on both sides and a microstructure of 10,000-mesh sandpaper. Subsequently, a glass sheet with a release film is covered to form a sealed structure, achieving a curing condition of water and oxygen isolation. S4 Photo-curing Polymerization Film Formation: Using an ultraviolet light source with a wavelength of 365 nm, curing is carried out for 1 hour under an irradiation intensity of 30 mW / cm 2 The cured film is peeled off from the silica gel sheet, and finally a polyionic liquid film with a thickness of 100 μm is obtained. After a tensile test, its modulus is calculated to be 0.8 MPa.

[0082] Performance Test Results of Polyionic Liquid Films Prepared According to Examples 1-3: In Example 1, the mass ratio of 1-vinyl-3-butylimidazolium tetrafluoroborate to diethylene glycol divinyl ether is 50:3, and its modulus is 31 MPa; in Example 2, the mass ratio is 50:6, and the modulus is 13 MPa; in Example 3, the mass ratio is 50:9, and the modulus is 0.8 MPa. It can be seen that as the amount of diethylene glycol divinyl ether increases, the soft segment content is more, and the modulus of the material is smaller. The lower the modulus, the more suitable it is for low-pressure testing, and the more sensitive the device is. Therefore, according to different application scenarios (MPa level or kPa level), the polyionic liquid film can be targeted to be regulated, thereby improving the accuracy and application range of the sensor.

[0083] (II) Processing Flexible Electrodes: The polyimide-copper substrate is processed by laser cutting. The cutting power is set at 30 W, the laser scanning speed is 100 mm / s, and the number of cutting times is 10 times. A left-right symmetric coil and electrode are prepared. The diameter of the unilateral circular electrode is 2 mm, the number of coil turns is 6, and the line width is 130 μm. The specific morphology is as shown in Figure 4 the upper right example in the figure.

[0084] (III) Assembling the Sensor:

[0085] (1) The poly(dimethylsiloxane) encapsulation layer (PDMS) and the polyimide surface of the polyimide-copper electrode are adhesively bonded after being plasma-activated by a plasma cleaner. The power is set at 40 W and the time is 1 min; the bonded device is placed in an oven, set at 70 °C, and taken out after 20 min.

[0086] (2) The polyionic liquid film is fixed at the center position of the coil of the flexible electrode and folded along the center line ( Figure 4 the red line marked in the figure) so that the two coils are aligned and overlapped, forming a sensor unit with a sandwich-like layered structure of electrode-polyionic liquid active layer-electrode.

[0087] (3) The entire sensor unit is hot pressed again to achieve complete encapsulation of the device.

[0088] Application Examples

[0089] The performance test of the wireless transmission type ionization pressure sensor prepared in Examples 1-3 was carried out, and the test method and results are as follows:

[0090] Test method: Place the sensor on the plane of the test circuit board, use a 2mm indenter to apply different pressures to the circular position above the device, connect the circuit board to a network analyzer, and read the resonant frequency data in real time. Record the changes in the resonant frequency while applying different pressure steps. In addition, during a long-term constant pressure test, add a circular plastic indenter to the circular position of the device, place a weight on top of the indenter, let the device stand for a while, and record the data of the resonant frequency changes over time before and after the weights are placed.

[0091] Test results: The resonant frequency of the sensor in Example 1 changes with pressure. Figure 5 As shown in Figure 1 (580-625MHz), the resonant frequency of the device changes under different pressures, and the slopes of the changes in the range of 0-20kPa and 20-200kPa are -1.5MHz kPa respectively. -1 ,-0.05MHz kPa -1 , with higher sensitivity and wider pressure measurement range. The resonant frequency sensing range of Example 2 is about 30MHz higher than that of Example 1 (varies in the range of 561-638MHz), and the sensitivity is slightly larger. The resonant frequency sensing range of Example 3 is about 20MHz higher than that of Example 1 (varies in the range of 259-327MHz), and the sensitivity in the low pressure (test below 10kPa) area is 1 times higher than that of Example 1.

[0092] It can be seen that the more diethylene glycol divinyl ether in the material, the more soft segment content, the lower the modulus, the larger the device range, and the more sensitive it is; the larger the number of coil turns, the range of change is in the lower frequency range. The reason is that the larger the number of turns, the greater the inductance of the device, and the frequency is inversely proportional to the inductance, so the frequency is smaller. Therefore, in the actual application process, the device can be prepared specifically according to the required frequency band by adjusting the amount of diethylene glycol divinyl ether and the number of coil turns.

[0093] The return loss curve of the sensor changes with frequency as shown in Figure 6 As shown in the figure, the quality factor (Q) value of the device is 74, which is one order of magnitude higher than that of ordinary ion gel devices and is at a relatively high level. The higher the quality factor, the sharper the return loss trough, and the smaller the f r The smaller the signal swing range at the trough, the smaller the signal noise, the higher the signal-to-noise ratio, and the more stable the signal performance.

[0094] The non-ion liquid leakage type ionized sensor in the constant pressure test under high pressure is as follows Figure 7 As shown, under a constant external force of 400 kPa, the noise level is only 0.3 MHz within 10 minutes; at the same time, it exhibits an excellent signal-to-noise ratio of 43 dB, which is 1.5 times that of ordinary dielectric elastomers and one order of magnitude higher than that of ordinary hydrogels; moreover, through the design of the polyion liquid molecular chain, it also has high signal stability, with a signal drift of only 0.5 MHz within 10 minutes, a drift ratio of only 1%, and the subsequent signal is stably output continuously for 10 s.

[0095] In summary, the operating principle and technical advantages of the wireless transmission type ionized pressure sensor based on non-liquid leakage provided by the present invention are as follows:

[0096] The system consists of a sensor and a frequency collector to form a dual-module system. Among them, the sensor is designed based on an inductor-capacitor (LC) resonance circuit, and its inductance parameter is determined by structural features such as coil size and number of turns. The capacitance comes from the ionized interface constructed by the polyion liquid electrolyte material, and its significant signal gain comes from two aspects: (1) the interface capacitance multiplication effect, the double-layer capacitance formed by the electrode and the ionic material at the interface has a very high charge density, which is 2-4 orders of magnitude higher than that of traditional flat capacitors; (2) three-dimensional contact strengthening, using a sandwich stacked electrode structure (non-planar interpolation design), the contact area between the ionic material and the electrode is expanded by 1-2 orders of magnitude, significantly broadening the sensing range. Then, a network analyzer is used to monitor the sensing signal, breaking through the limitation of wired connection and making data acquisition more flexible, efficient and extensive. When an external load acts on the device, the capacitance value increases, causing the resonance frequency to shift, and the mechanical signal is quantified by monitoring the change in frequency.

[0097] The ionized functional material used in the present invention also has the following two advantages. On the one hand, it is the stability of the functional material. The polyion liquid fixes some ions on the polymer chain by chemical bonds, effectively eliminating the risk of electrolyte leakage under high pressure, and avoiding signal drift caused by the penetration of the ion liquid during long-term constant pressure tests, with a signal drift of only 1%; on the other hand, it is the optimization of the signal-to-noise ratio. The use of polyionic materials significantly improves the quality factor of the device compared with traditional ion gel sensors, reduces the noise level by one order of magnitude, and increases the signal-to-noise ratio several times compared with traditional gel sensors.

[0098] Through the above experimental verification and analysis, it can be seen that through the innovation of the material system (leak - free polyionic liquid) and the optimization of the sandwich - stacking structure in the design of the present invention, the technical bottlenecks of traditional ion - electric sensors, such as limited high - voltage range, signal drift, and large background noise, have been overcome. By realizing the wireless acquisition of capacitance signals through the change of the acquisition frequency, the limitation of the wired acquisition of traditional sensors has been broken through, making data acquisition more flexible, efficient, and extensive, and showing high - precision and long - term stable wireless mechanical detection capabilities in fields such as real - time biomedical monitoring (such as cardiovascular pressure sensing) and status perception of human - machine interaction devices.

[0099] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and example. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many modifications and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical application so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A preparation method of a wireless transmission type off-electric pressure sensor based on no liquid leakage, characterized in that It includes the following steps: Prepare a polyionic liquid film without liquid leakage: Mix a monomer containing 1-vinyl-3-butylimidazolium cation, diethylene glycol divinyl ether, and an initiator in a certain mass ratio to form a homogeneous precursor; subject the precursor to curing polymerization to obtain a polyionic liquid film. Process a flexible electrode: Perform laser cutting on a polyimide-copper substrate to prepare a coil-electrode material. Assemble the sensor: (1) After plasma activation treatment of the polyimide surfaces of the encapsulation layer and the flexible electrode, perform thermocompression bonding. (2) Fix the polyionic liquid film at the center position of the coil of the flexible electrode, fold it along the center line so that the two coils of the flexible electrode are aligned and overlapped to form a sensor unit with a sandwich-like layered structure of electrode-polyionic liquid active layer-electrode. (3) Perform thermocompression on the overall sensor unit again to achieve complete encapsulation of the device, thus obtaining the product.

2. The preparation method of the wireless transmission type off-electric pressure sensor based on no liquid leakage as described in claim 1, characterized in that In the step of preparing a polyionic liquid film without liquid leakage, the anion in the monomer containing 1-vinyl-3-butyl imidazolium cation includes BF4 - 、N(CF3SO2)2 - Br - PF6 - 、NO3 - At least one of .

3. The preparation method of the non-contact power-off type pressure sensor based on wireless transmission without liquid leakage according to claim 1, characterized in that, In the step of preparing the polyionic liquid film without liquid leakage, the mass ratio of the monomer containing 1-vinyl-3-butylimidazolium cation to diethylene glycol divinyl ether is 50:(3-9).

4. The preparation method of the wireless transmission type off-electric pressure sensor based on no liquid leakage according to claim 1, characterized in that, In the step of preparing the polyionic liquid film without liquid leakage, the initiator includes ethyl 2,4,6-trimethylbenzoyl phenylphosphinate.

5. The preparation method of the wireless transmission type off-electric pressure sensor based on no liquid leakage according to claim 1, characterized in that In the step of preparing the polyionic liquid film without liquid leakage, the thickness of the obtained polyionic liquid film is 50-200 μm.

6. The preparation method of the wireless transmission type off - power pressure sensor based on no liquid leakage as claimed in claim 1, wherein, In the step of processing the flexible electrode, in the preparation of the coil-electrode, the coil and the electrode are centrosymmetric structures on the left and right. The diameter of the circular electrode on one side is 1-3 mm, the diameter of the coil is 3-6 mm, the number of turns of the coil is 3-7 turns, and the line width is 100-200 μm.

7. The preparation method of the non-contact power-off type pressure sensor based on wireless transmission without liquid leakage according to claim 1, wherein In the step of assembling the sensor, the encapsulation layer includes polydimethylsiloxane.

8. The preparation method of the wireless transmission type off-electric pressure sensor based on no liquid leakage according to claim 1, characterized in that The prepared wireless transmission type ionoelectric pressure sensor has a noise level of 0.3 MHz within 10 min under a constant external force of 400 kPa, and the drift ratio is only 1%, and there is no phenomenon of liquid leakage in the polyionic liquid material.

9. A wireless transmission type ionoelectric pressure sensor based on liquid leakage-free prepared by the method according to any one of claims 1-8.

10. Application of the wireless transmission type ionoelectric pressure sensor based on liquid leakage-free prepared by the method according to any one of claims 1-8 in human-computer interaction, health monitoring, electronic skin, and portable intelligent wearable devices.

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