Triboelectric humidity and pressure bimodal sensor and testing method thereof

Abstract

The invention discloses a triboelectric humidity and pressure bimodal sensor and a testing method thereof.The bimodal sensor comprises a sensor moderate sensing unit and a pressure sensing unit, the humidity sensing unit comprises PVA ionic gel with a microstructure and a PET substrate, and a wire is connected to the PVA ionic gel to output signals so as to monitor humidity changes; the pressure sensing unit comprises an upper copper electrode, a lower copper electrode and a dielectric layer which is arranged between the upper copper electrode and the lower copper electrode and is provided with magnetic fiber fluff sprayed with PVA ionic gel, when the pressure sensing unit is under pressure, the contact area of the fiber fluff and the electrodes is increased, and different electric signals are generated along with the change of the pressure. The device can realize real-time monitoring of the surface pressure and humidity of the object, has the advantages of high measurement precision, long service life and the like, and provides a new way for intelligent sorting and motion detection.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a triboelectric humidity and pressure dual-mode sensor and a testing method thereof. Background Art

[0002] Flexible electronic devices have attracted widespread attention in many fields such as personal health monitoring, health assessment and sports monitoring due to their soft and compliant characteristics. As a key technology in this field, flexible sensors are regarded as the key to opening a new digital world, greatly expanding their potential application scenarios and significantly improving the user's interactive experience. At present, flexible sensors have shown great influence in key application areas such as smart homes, health monitoring systems, and wearable devices. Among these sensors, pressure sensors have received special attention due to their wide application. They are used in many fields such as skin electronic devices, robot human-machine interfaces, and biomedicine. At the same time, humidity, as a key variable in our daily lives, can provide important information about living environment, medical conditions, and personal health status. Despite this, there are relatively few studies on humidity sensors, mainly because changes in humidity often affect the sensitivity of the sensor, thereby limiting its performance.

[0003] Common composite sensors usually integrate multiple sensing units into one sensor, each sensing unit performs its own function, and the values ​​of different physical quantities can be obtained by detecting the signals of each sensing unit during operation, realizing the function of detecting multiple physical quantities and having good detection performance. A flexible array humidity pressure sensor (CN114858339A) implemented by inkjet printing technology integrates humidity and pressure measurement units at the same time without interfering with each other. However, the composite sensor has a multilayer structure, so it is relatively complex, and because the sensor is based on the LC resonance principle, a relatively expensive network analyzer is required as a test equipment. ZnS:Mn and reduced graphene oxide are incorporated into an elastomer to obtain a temperature humidity pressure sensor (CN110793676A), which has the advantages of high integration, high resolution and high sensitivity. However, the preparation of the sensor requires processes such as photolithography in semiconductor production, and the process is complicated and the cost is high. When the sensor detects humidity, the response time takes tens of seconds, the reaction is slow, and the sensitivity of measuring humidity is low, less than 10MΩ / %RH. The principle of detecting humidity by this sensor is that the capacitance of graphene oxide increases with increasing humidity, but the capacitance of the elastomer PDMS also changes with increasing pressure, which causes the accuracy of the sensor in measuring humidity to decrease in the presence of pressure. Existing temperature and humidity pressure sensors (CN106568539A) also require processes such as photolithography in semiconductor production for manufacturing. The existing preparation method prepares porous PDMS flexible pressure sensors with a variety of pore sizes and pore structures. The maximum pressure sensitivity of the capacitive porous PDMS flexible pressure sensor is 0.0658KPa. -1 The use of conductive fillers or increasing the flexibility of the pore structure can increase the pressure sensitivity of the porous PDMS flexible pressure sensor, but the sensitivity does not exceed 1.7529KPa -1 .

[0004] The pressure sensitivity of the graphene-filled flexible pressure sensor (CN114479469A) does not exceed 76.321 kPa -1 , and as the pressure increases, the sensitivity decreases. When the conductive filler is conductive nano-carbon black, carbon nanotubes, graphene, Ag powder, Au powder or silver-coated copper powder, its pressure sensitivity does not exceed 7.29kPa-1. 3,4-ethylenedioxythiophene EDOT) / sodium polystyrene sulfonate (PSS) forms a conductive fabric (CN111609954A) and attaches it to a PDMS substrate to obtain a pressure sensor, but the sensitivity is low. The flexible capacitive pressure sensor (CN115096480A) is filled with carbon nanotubes and MXene, but the pressure sensitivity is also low. The pressure sensitivity of the multilayer composite pressure sensor (CN110501095A) does not exceed 507kPa -1, which is the most sensitive pressure sensor currently. The above pressure sensors have limited sensitivity or complex process when adding temperature and humidity sensing functions.

[0005] Therefore, there is an urgent need to develop a flexible sensor that can effectively detect pressure and humidity, and at the same time has the characteristics of high sensitivity and fast response time, so as to provide a basis for the industrialization of flexible sensing. Summary of the invention

[0006] The purpose of the present invention is to provide a flexible sensor with simple structure, high sensitivity, short response time and strong durability that can effectively detect pressure and humidity to meet the needs of flexible electronic devices in the fields of intelligent sorting and motion detection. Specifically, it is a triboelectric humidity and pressure dual-mode sensor and its test method, which can realize real-time monitoring of environmental humidity and pressure.

[0007] The present invention is achieved by at least one of the following technical solutions.

[0008] A triboelectric humidity and pressure dual-mode sensor comprises a humidity sensing unit and a pressure sensing unit, wherein the humidity sensing unit comprises a PVA ion gel with a microstructure and a PET substrate, wherein the PVA ion gel with a microstructure is connected to the PET substrate, wherein a wire is connected to the PVA ion gel with a microstructure for outputting an electrical signal; and the pressure sensing unit comprises an upper electrode, magnetic fiber fluff sprayed with the PVA ion gel, and a lower electrode, wherein wires are connected to the upper electrode and the lower electrode for outputting an electrical signal.

[0009] Furthermore, the humidity sensing unit is made of PDMS, and the thickness of the humidity sensing unit is 50 μm-70 μm.

[0010] Furthermore, the PVA ion gel with microstructure is prepared by spin coating polydimethylsiloxane on a stretched silicone substrate, and releasing the pre-stretching after solidification to naturally form a surface microstructure.

[0011] Furthermore, the microstructured PVA ion gel and the PET substrate are connected via a silicone adhesive.

[0012] Furthermore, the pressure sensing unit has a thickness of 5 mm to 8 mm.

[0013] Furthermore, the upper electrode and the lower electrode are made of copper.

[0014] Furthermore, the bottom of the magnetic fiber fluff sprayed with PVA ion gel is connected to the lower electrode through a silicone adhesive; the upper electrode is placed on the upper part of the magnetic fiber fluff sprayed with PVA ion gel, and the whole is packaged using a PI film to form a pressure sensing unit.

[0015] Furthermore, the PET substrate and the upper electrode are connected via a silicone adhesive.

[0016] Furthermore, the resistance of the PVA ion gel with microstructures decreases with the increase of ambient humidity;

[0017] When subjected to pressure, the contact area between the magnetic fiber fluff sprayed with PVA ion gel and the upper electrode increases, generating different electrical signals as the pressure changes.

[0018] A method for testing a triboelectric humidity and pressure dual-mode sensor according to any one of the above items comprises the following steps:

[0019] Step S1, using an electrostatic collection device to record the electrical signal generated by the triboelectric humidity and pressure dual-mode sensor, and converting the original sinusoidal signal into a square wave signal through a signal processing module to improve the signal stability and reduce the complexity of the detection signal;

[0020] Step S2, using a humidity detector to record the ambient humidity, and a pressure detector to record the external pressure applied to the triboelectric humidity-pressure dual-mode sensor;

[0021] Step S3: According to the output electrical signal and the recorded humidity and pressure, the ambient humidity is represented by voltage change, and the external pressure is represented by capacitance.

[0022] Compared with the existing technology, the testing method of the triboelectric humidity and pressure dual-mode sensor of the present invention has the following beneficial effects:

[0023] (1) For the sensor proposed in the present invention, when the ambient humidity changes, the resistance of the humidity sensing unit changes, and the output voltage signal changes synchronously with the change of humidity. Therefore, by collecting and summarizing the voltage values ​​of different ambient humidity, the functional relationship between ambient humidity and voltage can be obtained.

[0024] (2) The pressure sensing unit of the sensor proposed in the present invention is realized by covering the surface of the fiber fluff with an ion gel layer. Therefore, as the pressure increases, the contact area increases, and the capacitance value of the electrode interface also increases accordingly. The change in capacitance is directly converted into an electrical signal, allowing the sensor to sense and respond to smaller pressure changes. Since the fiber fluff is made of silicone and is elastic, it has an ultra-long service life and extremely high stability, as well as the advantages of self-driven sensing, a wide detection range, and high measurement accuracy.

[0025] (3) The present invention has the characteristics of miniaturization and integration, and can be applied to a variety of scenarios to achieve real-time monitoring of humidity and pressure without hindering the movement of objects, providing a theoretical and experimental basis for the development of new flexible electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of the triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0027] Figure 2 Schematic diagram of the working principle of the triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0028] Figure 3 is a response diagram of the humidity sensing unit in the triboelectric humidity and pressure dual-mode sensor of this embodiment to the detection of the ambient humidity signal;

[0029] Figure 4 This is a result diagram showing the effect of ambient humidity on the sensitivity of the humidity sensing unit in the triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0030] Figure 5 Result diagram of durability test of humidity sensing unit in triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0031] Figure 6 This is a graph showing the signal test results at different frequencies of the pressure sensing unit in the triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0032] Figure 7 This is a result diagram showing the effect of pressure on the sensitivity of the pressure sensing unit in the triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0033] Figure 8 is a result diagram of a durability test of a pressure sensing unit in the triboelectric humidity and pressure dual-mode sensor of this embodiment;

[0034] Explanation of the reference numerals: 1-humidity sensing unit; 11-PVA ion gel with microstructure; 12-PET substrate; 2-pressure sensing unit; 21-upper electrode; 22-magnetic fiber fluff sprayed with PVA ion gel; 23-lower electrode. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings:

[0037] like Figure 1As shown, the triboelectric humidity pressure dual-mode sensor structure of this embodiment is schematic. The triboelectric humidity pressure dual-mode sensor includes a humidity sensing unit 1 and a pressure sensing unit 2. The humidity sensing unit 1 includes a polyvinyl alcohol (PVA) ion gel 11 with a microstructure and a polyethylene terephthalate (PET) substrate 12. The microstructured PVA ion gel 11 and the PET substrate 12 are connected by a silicone adhesive, wherein the PVA ion gel 11 with a microstructure is connected with a wire for outputting an electrical signal to monitor humidity changes. The pressure sensing unit 2 includes an upper electrode 21, a magnetic fiber fluff 22 sprayed with PVA ion gel, and a lower electrode 23. The upper electrode 21 and the lower electrode 23 are connected with a wire for outputting an electrical signal. The magnetic fiber fluff 22 sprayed with PVA ion gel acts as a dielectric layer. When subjected to pressure, the contact area between the fiber fluff and the electrode increases, and different electrical signals are generated as the pressure changes.

[0038] The PVA ion gel 11 with microstructure is obtained by spin coating polyvinyl alcohol (PVA) on a pre-stretched substrate (silicone sheet), and releasing the pre-stretched naturally formed surface microstructure after solidification.

[0039] The specific preparation steps of the polyvinyl alcohol (PVA) ion gel 11 of this embodiment include: dissolving PVA in deionized water, wherein the molecular weight of PVA is 145000, the mass is 3g, and the mass of deionized water is 30g. Stirring for 2 hours at 90°C to completely dissolve it, then cooling to 50°C and adding 85% phosphoric acid (2.5 ml) as a cross-linking agent to promote the formation of a stable three-dimensional polymer network, stirring for 1 hour and fully mixing, coating the PVA solution on a PET substrate, controlling the thickness to be about 50-70μm, and then curing for 8 hours at 50°C in a constant temperature box to form an ion gel.

[0040] The specific preparation steps of the magnetic fiber fluff 22 are as follows: 10 ml of polydimethylsiloxane (PDMS) is prepared in a ratio of 1:1 between substrate and curing agent, and after stirring evenly, 6 g of hydroxy iron nanoparticles (diameter 500 nm) and 1 g of neodymium iron boron nanoparticles (2000 mesh) are added. After being fully stirred evenly with an electric stirrer, the mixture is spin-coated on a PET film with a thickness of 0.2 mm. After the spin-coated solution is stable, the PET film containing PDMS is placed on top of a strong magnet, and magnetic fiber fluff will grow under the action of the magnetic field. After waiting for 24 hours at room temperature for PDMS to completely solidify, the fiber fluff can be removed from the PET film, and then the PVA solution is sprayed on the surface of the magnetic fiber fluff 22 using a spray gun, and then placed in a constant temperature box at 50°C for 8 hours to cure to form an ion gel.

[0041] The bottom of the magnetic fiber fluff 22 sprayed with PVA ion gel is connected to the lower electrode 23 through a silicone adhesive; the upper electrode 21 is placed on the upper part of the magnetic fiber fluff 22 sprayed with PVA ion gel, and the whole is packaged into a pressure sensing unit 2 using a PI film.

[0042] The PET substrate 12 is connected to the upper electrode 21 by a silicone adhesive. As the ambient humidity increases, the resistance of the PVA ion gel 11 with a microstructure decreases, and the electrical signal changes accordingly. When subjected to pressure, the contact area between the magnetic fiber fluff 22 sprayed with the PVA ion gel and the upper electrode 21 increases, and different electrical signals are generated as the pressure changes.

[0043] As an embodiment, the PVA ion gel 11 with microstructure has an outer dimension of 10 mm×10 mm and a thickness of 50-70 μm. The pressure sensing unit 2 has an overall outer dimension of 10 mm×10 mm and a thickness of 5-8 mm.

[0044] As an embodiment, the upper electrode 21 and the lower electrode 23 are made of copper.

[0045] like Figure 2 As shown, the testing method of the triboelectric humidity and pressure dual-mode sensor specifically includes the following steps:

[0046] Step S1, using an electrostatic collection device to record the electrical signal generated by the triboelectric humidity and pressure dual-mode sensor, transmitting the signal to a computer through a programmable electrometer (6514, Keithley, USA) and a data acquisition system (PCI-6289, National Instruments, USA), and using LabVIEW to convert the original sinusoidal signal into a square wave signal to improve the signal stability and reduce the complexity of the detection signal;

[0047] Step S2, repeatedly placing a weight of a fixed weight on the surface of the triboelectric humidity and pressure dual-mode sensor of this embodiment to apply pressure, and using a humidity detector and a pressure detector to record the ambient humidity and the applied external pressure;

[0048] In step S2, the ambient humidity is recorded using a humidity detection device, and the applied ambient pressure is recorded by a pressure sensor;

[0049] Step S3: According to the output electrical signal and the recorded humidity and pressure, the ambient humidity is represented by voltage change, and the external pressure is represented by capacitance.

[0050] like Figure 3 FIG. 1 is a schematic diagram of the electrical signal output of the humidity sensor unit of this embodiment at different relative humidity. As the humidity decreases, the voltage signal increases.

[0051] like Figure 4 As shown in FIG. 1 , the sensitivity of the humidity sensor unit described in this embodiment is affected by the environmental humidity. When the relative humidity increases from 13.8% to 92%, the voltage sensitivity of the sensor decreases by 26.6 times. It can be seen from the figure that the determination coefficient R 2 Close to 1, showing good linearity.

[0052] like Figure 5 As shown in FIG. 1 , the results of the durability test of the humidity sensing unit in the triboelectric humidity and pressure dual-mode sensor of the present invention are shown. Figure 5 a is the test result on the first day under the environment of relative humidity of 80±2%. Figure 5 b is the test result on the second day under the environment of relative humidity of 80±2%. Figure 5 c is the test result in an environment with a relative humidity of 80±2%. The test results show that in the three-day test in the same humidity environment, the voltage change of the electrical signal is stable without obvious attenuation, reflecting the ultra-long service life of this design.

[0053] like Figure 6 As shown, it is a signal test result diagram of the pressure sensing unit in the triboelectric humidity and pressure dual-mode sensor described in the present invention at different frequencies. It can be seen that the change amplitude of the capacitor output signal at different frequencies is basically the same, and the frequency has no significant effect on the sensor signal output.

[0054] like Figure 7 As shown, the sensitivity of the pressure sensing unit of the present invention is affected by pressure, and the capacitance sensitivity S has good linearity.

[0055] like Figure 8 As shown, Figure 8 b is a result diagram of the durability test of the pressure sensing unit of the present invention, Figure 8 a is the signal amplification diagram in the initial stage. Figure 8 The c is the signal amplification diagram of the final stage. The experimental results show that after one hour of continuous pressing, the capacitor output voltage amplitude is still stable at 8.8V, without obvious attenuation, reflecting the ultra-long service life of this design.

[0056] A triboelectric humidity-pressure dual-modal sensor and a testing method thereof proposed in an embodiment of the present invention have the characteristics of miniaturization and integration, can detect environmental humidity and pressure without affecting the movement of the host device, and provide a theoretical and experimental basis for the development of new flexible electronic devices.

[0057] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. It can also be a reasonable combination of the features recorded in the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A triboelectric humidity and pressure dual-mode sensor, characterized in that: The invention comprises a humidity sensing unit (1) and a pressure sensing unit (2), wherein the humidity sensing unit (1) comprises a PVA ion gel (11) with a microstructure and a PET substrate (12), wherein the PVA ion gel (11) with a microstructure is connected to the PET substrate (12), wherein a wire is connected to the PVA ion gel (11) with a microstructure for outputting an electrical signal; and the pressure sensing unit (2) comprises an upper electrode (21), magnetic fiber fluff (22) sprayed with the PVA ion gel, and a lower electrode (23), wherein wires are connected to the upper electrode (21) and the lower electrode (23) for outputting an electrical signal.

2. A triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The material of the humidity sensing unit (1) is PDMS, and the thickness of the humidity sensing unit (1) is 50 μm-70 μm.

3. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The PVA ion gel (11) with microstructure is prepared by spin coating polydimethylsiloxane on a stretched silica gel substrate, and releasing the pre-stretching after solidification to naturally form a surface microstructure.

4. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The microstructured PVA ion gel (11) and the PET substrate (12) are connected via a silicone adhesive.

5. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The pressure sensing unit (2) has a thickness of 5 mm to 8 mm.

6. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The upper electrode (21) and the lower electrode (23) are made of copper.

7. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The bottom of the magnetic fiber fluff (22) sprayed with PVA ion gel is connected to the lower electrode (23) through a silicone adhesive; the upper electrode (21) is placed on the upper part of the magnetic fiber fluff (22) sprayed with PVA ion gel, and the whole is packaged with a PI film to form a pressure sensing unit (2).

8. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: The PET substrate (12) and the upper electrode (21) are connected via a silicone adhesive.

9. The triboelectric humidity and pressure dual-mode sensor according to claim 1, characterized in that: As the ambient humidity increases, the resistance of the microstructured PVA ion gel (11) decreases; When subjected to pressure, the contact area between the magnetic fiber fluff (22) sprayed with PVA ion gel and the upper electrode (21) increases, and different electrical signals are generated as the pressure changes.

10. A method for testing a triboelectric humidity and pressure dual-mode sensor as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: Step S1, using an electrostatic collection device to record the electrical signal generated by the triboelectric humidity and pressure dual-mode sensor, and converting the original sinusoidal signal into a square wave signal through a signal processing module to improve the signal stability and reduce the complexity of the detection signal; Step S2, using a humidity detector to record the ambient humidity, and a pressure detector to record the external pressure applied to the triboelectric humidity-pressure dual-mode sensor; Step S3: According to the output electrical signal and the recorded humidity and pressure, the ambient humidity is represented by voltage change, and the external pressure is represented by capacitance.

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