Electric field enhanced self-powered humidity sensor and preparation method and application thereof

Abstract

The invention relates to the technical field of humidity sensors, and particularly discloses an electric field enhanced self-powered humidity sensor and a preparation method and application thereof. The sensor sequentially comprises an aluminum electrode layer, a filter paper middle layer and a copper electrode layer from top to bottom, the copper electrode layer completely coincides with the lower surface of the filter paper middle layer, the aluminum electrode layer covers 60%-80% of the area of the upper surface of the filter paper middle layer, 20%-40% of the area of the upper surface of the filter paper middle layer is an exposed area, and the aluminum electrode layer and the copper electrode layer form an asymmetric metal electrode. The middle layer of the filter paper is coated with a sensitive material, and the sensitive material is a potassium chloride modified h-C3N4 / PVA composite material. According to the invention, the potassium chloride modified h-C3N4 / PVA composite material is adopted as a sensitive material, the asymmetric metal electrodes are introduced into the sandwich structure, and an internal electric field consistent with the water diffusion direction is generated in the sensitive layer by utilizing a humidity-induced primary battery effect, so that the output voltage and the response speed of the sensor are remarkably improved, and the sensitivity of the sensor is improved. And finally, excellent response performance is shown.

Description

Technical Field

[0001] This invention relates to the field of humidity sensor technology, and in particular to an electric field-enhanced self-powered humidity sensor, its fabrication method, and its application. Background Technology

[0002] The sustainable development and low-power requirements of sensor nodes in the Internet of Things (IoT) are driving the development of low-power (or even zero-power) electronic devices. Humidity, as a key environmental parameter, has significant applications in numerous fields such as food preservation, agricultural monitoring, and industrial production. Therefore, developing integrated sensors that combine power generation and humidity detection functions provides a new technological path for achieving self-powered humidity detection.

[0003] Among various self-powered technologies, moisture generators (MEGs), based on an asymmetric ion motion mechanism, can achieve stable electrical output without relying on external mechanical energy, offering greater continuous reliability compared to triboelectric nanogenerators (TENGs), and thus have attracted widespread research attention. However, existing MEGs still have significant shortcomings when used for humidity sensing, mainly manifested in low response voltage, limited sensitivity, and slow response speed, making it difficult to meet the requirements for accurate and rapid humidity detection. These problems mainly stem from the following two factors: First, the diffusion ability and speed of water molecules in the sensing material are not conducive to the diffusion of generated ion pairs, resulting in poor sensitivity and slow response speed. Second, the limited ionization ability of water molecules cannot generate a sufficient number of positive and negative ion pairs, resulting in a small potential difference across the device. Numerous researchers have conducted studies to improve the sensing performance of humidity sensors based on microelectronic generators (MEGs), employing strategies such as constructing functional group gradients, introducing heterogeneous functional structures, and designing dry and wet regions. These strategies aim to enhance the humidity gradient differences within the sensor and improve ion diffusion capabilities. However, certain drawbacks remain. For instance, relying on the difference between dry and wet regions or the design of gradient structures makes them susceptible to interference in real-world dynamic humidity environments, resulting in insufficient gradient stability and consequently, sensor output drift and poor repeatability. Existing strategies offer limited improvement in water ionization efficiency, and the number of ion pairs generated remains insufficient, leading to modest increases in output potential and sensitivity, making it difficult to meet the demands of high-precision detection.

[0004] Therefore, how to construct an internal electric field within a self-powered sensor to achieve the synergistic effect of the electric field and humidity gradient, while simultaneously addressing the core issues of slow ion diffusion and low ionization efficiency, has become a key area for breakthrough in the current field of self-powered humidity sensing technology. Developing a simple, high-performance, and scalable electric field-enhanced self-powered humidity sensor has significant theoretical and engineering value for promoting the development of IoT sensing technology and expanding the practical applications of self-powered sensors in various fields. Summary of the Invention

[0005] To address the above shortcomings, this invention provides an electric field-enhanced self-powered humidity sensor, its fabrication method, and its application. By enhancing the internal electric field, it improves the efficient humidity sensing performance of the wet generator, significantly increasing the sensor's output voltage and response speed. The specific technical solution is as follows: An electric field-enhanced self-powered humidity sensor, comprising, from top to bottom: an aluminum electrode layer, a filter paper intermediate layer, and a copper electrode layer, wherein the copper electrode layer completely overlaps with the lower surface of the filter paper intermediate layer, the aluminum electrode layer covers 60-80% of the upper surface area of ​​the filter paper intermediate layer, 20-40% of the upper surface area of ​​the filter paper intermediate layer is an exposed area, the aluminum electrode layer and the copper electrode layer constitute an asymmetric metal electrode, and the filter paper intermediate layer is coated with a sensitive material, wherein the sensitive material is a potassium chloride-modified h-C3N4 / PVA composite material.

[0006] The humidity sensor of this invention uses potassium chloride-modified h-C3N4 / PVA composite material as the sensitive material and introduces asymmetric metal electrodes into the sandwich structure. By utilizing the humidity-induced galvanic cell effect, an internal electric field consistent with the water diffusion direction is generated inside the sensitive layer, thereby significantly improving the sensor's output voltage and response speed. It can generate a directional electric field inside the sensor without the need for an external power source, further promoting the directional migration of ions inside the self-powered sensor. Compared with the original MEGs-based sensor, its output voltage is significantly improved and the response time is significantly shortened, exhibiting superior sensing performance.

[0007] Preferably, in the above-mentioned electric field-enhanced self-powered humidity sensor, the filter paper is water-based porous with a pore size of 20-25 μm, the potassium chloride-modified h-C3N4 particles have a particle size of 200-300 nm, and the aluminum electrode layer and copper electrode layer have a thickness of 50-65 μm. The potassium chloride-modified h-C3N4 / PVA composite material of the present invention, after modification with potassium chloride, can regulate the charge transfer performance of the sensitive material. Furthermore, the presence of multiple functional groups helps to generate more positive and negative charge pairs after water molecule adsorption. This effect is beneficial to improving the sensor's response voltage. Additionally, the surface hydrophilicity and reaction site density of the potassium chloride-modified h-C3N4 are enhanced, thereby improving the humidity sensor's low humidity detection and response speed, among other humidity sensitivity performance characteristics.

[0008] Preferably, in the above-mentioned electric field-enhanced self-powered humidity sensor, the exposed area occupies 30% of the upper surface of the filter paper intermediate layer.

[0009] On the other hand, the present invention also provides a method for preparing the above-mentioned electric field-enhanced self-powered humidity sensor, comprising the following steps: (1) Preparation of potassium chloride modified h-C3N4 material; (2) Potassium chloride modified h-C3N4 material was mixed with PVA to prepare potassium chloride modified h-C3N4 / PVA composite material; (3) The filter paper was impregnated with potassium chloride-modified h-C3N4 / PVA composite material and dried to obtain the modified filter paper; (4) Aluminum electrodes and copper electrodes are respectively covered on the upper and lower surfaces of the modified filter paper to obtain a humidity sensor.

[0010] Preferably, in the above-mentioned method for preparing an electric field-enhanced self-powered humidity sensor, step (1) specifically includes: grinding and mixing NH4SCN and KCl, and then calcining them at 500~600℃; dialyzing the calcined powder in a dialysis bag and vacuum drying it to obtain potassium chloride-modified h-C3N4; adding PVA particles to the potassium chloride-modified h-C3N4 to obtain a potassium chloride-modified h-C3N4 / PVA composite material.

[0011] Preferably, in the above-mentioned method for preparing an electric field-enhanced self-powered humidity sensor, the weight ratio of NH4SCN to KCl is 8~12:1.

[0012] Preferably, in the above-mentioned method for preparing an electric field-enhanced self-powered humidity sensor, step (2) specifically includes: adding potassium chloride-modified h-C3N4 material and PVA to deionized water, ultrasonically dispersing for 5-10 minutes to obtain potassium chloride-modified h-C3N4 / PVA composite material.

[0013] Preferably, in the above-mentioned method for preparing an electric field-enhanced self-powered humidity sensor, the mass ratio of the potassium chloride-modified h-C3N4 material to PVA is 1~2:1~2.

[0014] Preferably, in the above-mentioned method for preparing an electric field-enhanced self-powered humidity sensor, step (3) specifically includes: immersing filter paper in potassium chloride-modified h-C3N4 / PVA composite material for 45-75 minutes, then drying it at 60-70°C, repeating the immersion-drying process 3-4 times to obtain modified filter paper. The method of impregnating and drying the sensitive material improves the uniformity and adhesion stability of the sensitive material.

[0015] On the other hand, the present invention also provides the application of the above-mentioned electric field-enhanced self-powered humidity sensor in real-time monitoring of moisture information.

[0016] On the other hand, the present invention also provides the application of the above-mentioned electric field-enhanced self-powered humidity sensor in the preparation of non-contact switches, non-contact keyboards, and / or respiratory disease monitoring devices.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The electric field-enhanced self-powered humidity sensor of the present invention uses potassium chloride-modified h-C3N4 / PVA composite material as the sensitive material and introduces an asymmetric metal electrode in the sandwich structure. By utilizing the humidity-induced galvanic cell effect, an internal electric field consistent with the water diffusion direction is generated inside the sensitive layer, realizing the synergistic effect of the electric field and humidity gradient, thereby significantly improving the output voltage and response speed of the sensor, and ultimately exhibiting excellent response performance.

[0018] 2. The Al-filter paper-Cu sandwich structure of this invention acts as a galvanic cell. Electrons transfer from Al to Cu through an external circuit, thereby forming an internal electric field from Al to Cu within the filter paper. This internal electric field is aligned with the water diffusion direction, promoting the diffusion of H3O. + This improves the diffusion capability, thereby increasing the output voltage and response speed of the E-MEG.

[0019] 3. The sandwich structure sensor prepared in this invention, based on potassium chloride-modified h-C3N4 / PVA as the sensing material, is an electric field-enhanced self-powered humidity sensor. It achieves the synergistic effect of the electric field and humidity gradient, ultimately exhibiting excellent response performance. Within a wide relative humidity (RH) range of 22.6%-93%, the sensor demonstrates higher response voltage, minimal delay effect, and stable point response characteristics. Furthermore, experimental comparisons confirm the superiority of the electric field-enhanced mode in the self-powered field, and the feasibility of the electric field-enhanced mode gain is revealed through original characterization and a series of electrical tests. The presence of an electric field has been shown to effectively promote the directional movement of H+, providing a new approach for the future development of self-powered humidity sensors.

[0020] 4. This invention proposes a working mode that promotes water diffusion gradient through an electric field to achieve high-performance self-powered humidity detection. It can generate a directional electric field inside the sensor without an external power source. A humidity sensor based on electric field-enhanced microelectronics generation (E-MEG) is rationally designed, further promoting the directional migration of ions inside the self-powered sensor. At a relative humidity (RH) of 89.2%, compared with the original MEG-based sensor, its output voltage is improved and the response time is significantly shortened, exhibiting superior sensing performance. The electric field-enhanced self-powered sensor proposed in this invention provides a new approach for the future improvement and development of self-powered devices. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the electric field-enhanced self-powered humidity sensor based on h-C3N4 / PVA composite material of the present invention, and a schematic diagram of the working principle of modulating the water diffusion gradient by electric field. Figure 2 This is a comparison diagram of the working principles of three humidity sensors based on h-C3N4 / PVA composite materials, which modulate the water diffusion gradient using an electric field. Figure 3 These are XRD patterns of h-C3N4, PVA, and h-C3N4 / PVA prepared in Example 1 of this invention; Figure 4 These are the FTIR spectra of h-C3N4, PVA, and h-C3N4 / PVA prepared in Example 1 of this invention; Figure 5 The contact angle test curves are of the untreated filter paper of the present invention and the h-C3N4 / PVA / filter paper prepared in Example 1. Figure 6 The output voltage comparison curves of the electrochemical sensor (ECH), the MEG-based sensor, and the E-MEG sensor at different exposure areas under 89.2% relative humidity are shown. Figure 7 These are comparison curves of the output voltage of an electrochemical sensor (ECH), a MEG-based sensor, and an E-MEG sensor at different relative humidity (RH) levels. Figure 8 This is a comparison of the response / recovery times of electrochemical sensors (ECH), MEG-based sensors, and E-MEG sensors at 89.2% RH; Figure 9 This is the humidity hysteresis curve of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of the present invention; Figure 10 These are the output curves of the electric field-enhanced self-powered humidity sensor prepared in Embodiment 1 of the present invention under forward and reverse connection conditions; Figure 11 This is a repeatability test of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of the present invention for different RH values; Figure 12 This is a comparison of the output voltage of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of the present invention in air and air containing interfering gas (500 ppm); Figure 13 This is the continuous output voltage curve of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of the present invention over 7 hours; Figure 14 This is a long-term stability test of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of the present invention over 14 days; Figure 15 The electric field-enhanced self-powered humidity sensor of this invention, under the assistance of the electric field inside the main battery, generates H3O in the sensor. + A schematic diagram illustrating how diffusion is enhanced and the output voltage is further increased; Figure 16 This describes the effect of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of this invention on the sensor output voltage under ultraviolet irradiation at 60%RH. Figure 17 This describes the effect of an external electric field on the output voltage of the electric field-enhanced self-powered humidity sensor prepared in Embodiment 1 of the present invention. Figure 18 This is the electrochemical impedance spectroscopy of the electric field-enhanced self-powered humidity sensor prepared in Example 1 of this invention; Figure 19 This is a schematic diagram of the electric field-enhanced self-powered humidity sensor prepared in Embodiment 1 of the present invention used as a respiratory detection sensor; Figure 20 These are the output voltage curves of the electric field-enhanced self-powered humidity sensor prepared in Embodiment 1 of the present invention under different breathing modes; Figure 21 This is a comparison curve of the sensor prepared in Example 1 of the present invention for mouth breathing and nasal breathing; Figure 22 This refers to the real-time monitoring of the sensor prepared in Embodiment 1 of the present invention under cough mode; Figure 23 This is a demonstration of the application of the sensor prepared in Embodiment 1 of the present invention in speech recognition capability; Figure 24 This is the output voltage curve of the electric field-enhanced self-powered humidity sensor used as a non-contact switch at different proximity distances, prepared according to Embodiment 1 of the present invention. Figure 25 The output voltage curve of the electric field-enhanced self-powered humidity sensor prepared in Embodiment 1 of the present invention is a simulated non-contact keyboard. Figure 26 This is a schematic diagram of the "N"-shaped trajectory of a finger sliding on the sensor array prepared in Embodiment 1 of the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0024] Combination Figure 1 As shown, this invention provides a self-powered humidity sensor (E-MEG sensor) for an electric field-enhanced humidity generator based on potassium chloride-modified h-C3N4 / PVA composite material. The sensor consists of two asymmetric electrodes and a filter paper sandwiched in between. The copper electrode completely covers one side of the filter paper, while the aluminum electrode covers the other side, leaving a partially exposed area for water adsorption, thereby ensuring that the electric field and humidity gradient field are superimposed in the same direction. At the same time, in order to enhance the hydrophilicity and ion concentration of the filter paper, potassium chloride-modified hydrophilic h-C3N4 and PVA are coated on the filter paper by dip coating. The E-MEG sensor has a copper-aluminum sandwich structure, with an exposed area left on the side covered by the aluminum electrode. It has a high output voltage and fast response, and the humidity gradient is enhanced by the electric field.

[0025] Figure 2 The diagram shows a comparison of three types of sensors. The MEG sensor and ECH sensor in the diagram represent existing sensor structures. The MEG sensor is a sandwich structure with copper electrodes on both sides, leaving an exposed area on one side. It has a low output voltage and slow response speed, and is driven only by the humidity gradient. The ECH sensor has copper and aluminum electrodes on the same side, leaving an exposed area in the middle. It has a limited humidity gradient, a moderate output voltage, and is driven by the redox reaction.

[0026] The sensitive material is a potassium chloride-modified h-C3N4 / PVA composite material. The Al-filter paper-Cu sandwich structure acts as a galvanic cell, with electrons transferring from Al to Cu through an external circuit. This creates an internal electric field in the filter paper, oriented from Al to Cu. This internal electric field aligns with the water diffusion direction, promoting the diffusion of H3O. + This improves the diffusion capability, thereby increasing the output voltage and response speed of the E-MEG.

[0027] In an optional embodiment, the h-C3N4 / PVA composite material comprises potassium chloride-modified hydrophilic h-C3N4 and PVA crystal particles incorporated therein, constituting a potassium chloride-modified h-C3N4 / PVA composite material. After potassium chloride modification, the charge transfer properties of the sensitive material can be adjusted, and the presence of multiple functional groups helps to generate more positive and negative charge pairs after water molecule adsorption. This effect is beneficial to improving the response voltage of the sensor, and the surface hydrophilicity and reaction site density of the potassium chloride-modified h-C3N4 are enhanced. The introduction of h-C3N4 / PVA is beneficial to improving the humidity sensitivity performance of the humidity sensor, such as low humidity detection and response speed.

[0028] Example 1 An electric field-enhanced self-powered humidity sensor comprises, from top to bottom: an aluminum electrode layer, a filter paper intermediate layer, and a copper electrode layer. The copper electrode layer completely overlaps with the lower surface of the filter paper intermediate layer. The aluminum electrode layer covers 70% of the upper surface area of ​​the filter paper intermediate layer, with 30% of the upper surface of the filter paper intermediate layer being the exposed area. The aluminum electrode layer and the copper electrode layer constitute an asymmetric metal electrode. The filter paper intermediate layer is coated with a sensitive material, which is a potassium chloride-modified h-C3N4 / PVA composite material.

[0029] The filter paper has a size of 10×8 mm. 2 The aluminum electrode size is 7×8mm. 2 It covers the surface of the filter paper and leaves a partially exposed area for water adsorption; the size of the exposed area is 3×8 mm. 2 The copper electrode dimensions are 10 × 8 mm. 2 It completely covers the other surface of the filter paper.

[0030] This embodiment also provides a method for fabricating an electric field-enhanced self-powered humidity sensor, comprising the following steps: (1) Preparation of potassium chloride modified h-C3N4 material: Step 1-1: h-C3N4 is prepared by salt-assisted calcination. 10g of NH4SCN and 1g of KCl are ground together to obtain a mixed powder. Step 1-2: Transfer the mixed powder from Step 1-1 to a muffle furnace and calcine it at 550°C for 4 hours at a heating rate of 6°C / min. After naturally cooling to room temperature in steps 1-3, the powder calcined in step 2-2 is dialyzed in a dialysis bag for 24 hours to remove excess KCl, and then dried in a vacuum oven at 60°C for 24 hours to obtain potassium chloride modified h-C3N4 material.

[0031] (2) Preparation of potassium chloride modified h-C3N4 / PVA composite material: Add 30 mg of the prepared potassium chloride-modified h-C3N4 material and 30 mg of PVA (polyvinyl alcohol, molecular weight 200,000~220,000) to 2 ml of deionized water and disperse in an ultrasonic machine for 5 minutes to obtain a potassium chloride-modified h-C3N4 / PVA composite material dispersion. (3) Fabrication of a self-powered humidity sensor: Step 3-1: Immerse a filter paper in the potassium chloride modified h-C3N4 / PVA composite material dispersion of step (2) for 60 minutes, then remove the filter paper and dry it in a drying oven at 60°C; repeat the immersion-drying process 4 times to obtain the modified filter paper. Step 3-2: Sandwich the modified filter paper from Step 3-1 between copper and aluminum strips. The copper strip completely covers one surface of the filter paper, while the aluminum strip covers 70% of the other surface, leaving a 30% exposed area for water adsorption. Specifically, the copper and aluminum strips are approximately 60µm thick, with the copper strip measuring 10×8mm. 2 The aluminum strip size is 7×8mm 2 The exposed area of ​​the aluminum electrode is 3×8mm. 2 The filter paper is a superhydrophilic porous substrate made of paper fiber (manufacturer: Cytiva (Whatman), model 1004-110), with dimensions of 10×8mm. 2 The pore size is 20-25um.

[0032] Test case (1) Microstructure testing The XRD patterns of the h-C3N4 material, pure PVA, and h-C3N4 / PVA composite material prepared in Example 1 are as follows: Figure 3 As shown, for pure h-C3N4, the spectrum shows that the main diffraction peaks correspond to the relative crystal planes of carbon nitride, proving that h-C3N4 has been successfully synthesized. The XRD pattern of h-C3N4 shows a periodic in-plane heptaazine structure (8.1° and 9.9°), indicating that K + The doping was incorporated into the structure. Similarly, the PVA sample exhibited three characteristic diffraction peaks, corresponding to the PVA crystal planes (JCPDS NO. 65-2870). In the XRD pattern of the h-C3N4 / PVA composite, all characteristic peaks of PVA and h-C3N4 were preserved, maintaining the crystal integrity of both components and confirming the successful preparation of the h-C3N4 / PVA composite.

[0033] like Figure 4As shown, FTIR spectroscopy was used to study the chemical structure and potential hydrophilicity of the pure h-C3N4, pure PVA, and h-C3N4 / PVA composite materials prepared in Example 1. After the introduction of PVA, in addition to the characteristic peaks of h-C3N4, other peaks were observed in the 2800-3000 cm⁻¹ range. -1 Within this range, distinct PVA characteristic peaks can be observed, indicating that PVA has been successfully introduced. (3400-3700 cm⁻¹) -1 The significantly enhanced peak intensity within the range is attributed to the abundant hydroxyl content in PVA, which also indicates that the introduction of PVA is expected to further improve the hydrophilicity of the sensitive material.

[0034] like Figure 5 As shown, the improvement in hydrophilicity after adding moisture-sensitive material is visually evaluated by testing the water contact angle. The contact angles of filter paper and h-C3N4 / PVA / filter paper are displayed. Both have contact angles less than 90° and return to zero within one second, indicating that the filter paper itself has superhydrophilicity, which is beneficial for adsorbing ambient humidity. At the same time, it was observed that the contact angle of the filter paper after immersion in moisture-sensitive material is even smaller and returns to zero faster, showing better hydrophilicity.

[0035] The above results demonstrate that the present invention successfully prepared h-C3N4 / PVA, and also prove that the material has excellent hydrophilicity.

[0036] (2) Humidity sensitivity test Comparison of three sensors (structure as follows) Figure 2 As shown, the sensitive materials are all the same (such as those prepared in Example 1), and their properties are as follows: Figure 6 As shown, the exposure area (with a fixed width of 8 mm and a filter paper size of 10 mm) was studied. 8mm 2 The effect of the exposed area on humidity sensing performance at 89.2% relative humidity (RH): Too small an exposed area will hinder the adsorption of water molecules for further diffusion, while too large an exposed area will lead to excessive adsorption of water molecules and induce partial hydrolysis of the sensing material, ultimately resulting in discontinuous charge-ion conduction. The optimal exposed area for MEG is 30% (3 8 mm 2 The optimal exposure area for ECH is 10% (1 8 mm 2 The optimal exposure area for E-MEG is 30% (3 8 mm 2 With the same exposure area, the E-MEG sensor of the present invention has a higher output voltage and better response performance.

[0037] The humidity sensing performance of the three sensors was compared and evaluated within the RH range of 22.6%–93.0% at their respective optimal exposure areas. Figure 7 As shown, the three sensors exhibit similar sensing behavior trends when using different sensing materials, demonstrating the universality of this working principle. Among them, the E-MEG sensor of this invention has higher response performance and sensitivity.

[0038] A comparative test of the response and recovery times of the three sensors at their respective optimal exposure areas (at 89.2% RH) is as follows: Figure 8 As shown, E-MEGs have a faster response speed than MEG-based sensors and electrochemical sensors, but the water diffusion promoted by E-MEGs is detrimental to the water desorption process (which is opposite to the direction of water diffusion), resulting in a slightly longer recovery time.

[0039] like Figure 9 As shown, the E-MEG humidity sensor prepared in Example 1 of the present invention has a hysteresis of approximately 4.9% relative humidity (RH), demonstrating low hysteresis in water adsorption / desorption.

[0040] like Figure 10 As shown, the response and recovery curves of the E-MEG sensor prepared in Example 1 of the present invention are displayed under positive and negative electrode connection, which are consistent with the typical positive and negative electrode characteristics of a battery.

[0041] To further ensure reliability at various RH values, repeatability tests were performed at different RH levels, such as... Figure 11 As shown, E-MEG maintained excellent repeatability under all these humidity conditions, further confirming its good reliability.

[0042] like Figure 12 As shown, considering the potential impact of interfering gases on the electrical performance of the humidity sensor in the actual environment, the sensor was tested for its anti-interference capability: compared with the response voltage in the air environment, when the E-MEG was exposed to the air environment containing the above-mentioned interfering gases, the response voltage remained stable, indicating that it has good anti-interference capability.

[0043] like Figure 13 As shown, the durability of the E-MEG at 89.2% RH is demonstrated: although the output voltage decreases slightly over time, it still maintains 80% of the original high output voltage after more than 9 hours of continuous testing, proving its acceptable durability in high humidity environments.

[0044] like Figure 14 As shown, the voltage fluctuation is minimal (<5.7%) under different humidity conditions, indicating that E-MEG has excellent long-term electrical reliability.

[0045] In summary, the humidity sensor prepared by this invention achieves the synergistic effect of electric field and humidity gradient, thereby significantly improving the sensor's output voltage and response speed, ultimately exhibiting excellent response performance, good repeatability, durability, anti-interference performance, and long-term stability.

[0046] (3) Sensing mechanism like Figure 15 As shown, this illustrates the effect of H3O in the E-MEG under the assistance of the internal electric field of the main battery. + A schematic diagram illustrating diffusion enhancement and further increase in output voltage: Water molecules are adsorbed onto the surface of the sensing material due to electrostatic attraction or hydrogen bonding, and tend to dissociate into H+ in high humidity environments. + and OH - H + It combines with water molecules to form H3O + (Through the reaction H2O + H + → H3O + This further enhances proton transfer between water molecules through the "Grotes mechanism." Due to the asymmetry of water distribution between the exposed area (wet) and the relatively covered area (dry), the humidity gradient in the paper substrate drives H3O. + An induced potential is formed in the filter paper substrate by diffusion towards the dry area. Simultaneously, the induced electric field tends to force H3O... + Drifting towards moist areas, causing H3O + A dynamic balance is achieved between diffusion and drift motion, thereby forming a stable output voltage.

[0047] To investigate the effect of the existing humidity gradient on the response voltage, the sensor surface was irradiated with ultraviolet (UV) light under laboratory conditions (60%RH). Figure 16 As shown: When ultraviolet light irradiates the exposed area, the surface temperature of the filter paper increases, causing surface water molecules to evaporate, thereby reducing the water molecule concentration in the high humidity area (exposed area). This reduces the humidity gradient difference between the two sides of the device, which in turn weakens the ability of charge carriers to diffuse with humidity, thus reducing the response voltage.

[0048] The effect of the vertical electric field on the output performance of an E-MEG-based sensor (at 75% humidity) is demonstrated as follows: Figure 17 As shown, the output voltage is enhanced under a positive electric field and suppressed under a negative electric field. Simultaneously, the response speed follows a similar trend (4 seconds for positive voltage, 7 seconds for no voltage, and 15 seconds for reverse voltage), indicating that the output performance of the E-MEG is enhanced under a positive electric field.

[0049] like Figure 18 As shown, electrochemical impedance spectroscopy (EIS) further revealed the effects of electric field modulation on H3O. + The directional migration ability of ions.

[0050] (4) Multifunctional application like Figure 19 As shown, to achieve respiratory signal monitoring, the E-MEG sensor of this invention is integrated into the mask for exhalation detection. Specifically, the E-MEG sensor prepared in Example 1 of this invention is pasted onto the breathing area of ​​the mask, achieving integrated sensor-mask integration. The test results are as follows: Figure 20 As shown, the voltage intensity and interval of the output voltage differ for different oral breathing behaviors (slow breathing, normal breathing, and fast breathing). The interval and intensity of the output voltage can distinguish different breathing patterns, indicating that E-MEG has good discriminative ability.

[0051] Due to the enhanced sensitivity of E-MEG to humidity, this invention can also detect nasal breathing behaviors such as... Figure 21 As shown, the response amplitude fluctuates significantly during oral breathing, while the response amplitude fluctuates only slightly during nasal breathing. This is mainly attributed to the higher humidity environment during oral breathing compared to nasal breathing.

[0052] like Figure 22 As shown, this application demonstrates its use in monitoring bronchial asthma or cough: when coughing continuously for a short period of time, the output voltage increases, and after setting an alarm threshold, a real-time alarm can be triggered for the disease.

[0053] like Figure 23 As shown, this invention utilizes the non-contact speech recognition capabilities of E-MEG: when short syllable words (such as "a") are uttered, the sensor's output voltage signal changes slightly; when long monosyllable words (such as "an") and the disyllabic word "apple" are uttered, the output voltage increases. This demonstrates that E-MEG can effectively recognize words with different syllables and complete sentences, providing a new strategy for the development of subsequent self-powered speech recognition systems. The specific principle is that the exhaled humidity time and dryness / wetness vary when different speech sounds are uttered; the sensor can directly convert the speech's own energy into electrical energy, which is then combined with the algorithm to complete speech recognition.

[0054] To investigate the feasibility of E-MEG in contactless switching applications, the sensor's response to a finger relative to different gaps was verified. Figure 24-25As shown, as the spatial distance between the finger and the sensor gradually increases (5mm, 10mm, 15mm), the output voltage response gradually decreases, exhibiting good spatial distance resolution. When a finger approaches a single sensor, 0 and 1 are used as digital signal outputs, where 0 indicates no signal and 1 indicates a signal. This is suitable for further switching applications. This is mainly due to the excellent humidity sensitivity of the E-MEG sensor. The finger itself has a certain degree of humidity, and when the finger approaches the sensor, it generates a voltage, causing a change in the signal. This demonstrates the enormous potential application prospects of the E-MEG sensor in non-contact switches, human-machine interaction, and device control. When applied to non-contact panels, it has long-term working capability and avoids bacterial / viral infection that may occur with direct touch.

[0055] like Figure 26 As shown, the sensor array effectively identifies changes in the humidity field caused by finger swipes, with a typical "N"-shaped swipe trajectory plotted above the sensor array. The sensor array is then used to simulate a contactless keyboard application. The results demonstrate that the sensor array can accurately identify approaching fingers and exhibits good anti-interference capabilities, proving its significant application potential in contactless keyboards.

[0056] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An electric field-enhanced self-powered humidity sensor, characterized in that, The sensor comprises, from top to bottom, an aluminum electrode layer, a filter paper intermediate layer, and a copper electrode layer. The copper electrode layer completely overlaps with the lower surface of the filter paper intermediate layer. The aluminum electrode layer covers 60-80% of the upper surface area of ​​the filter paper intermediate layer. 20-40% of the upper surface area of ​​the filter paper intermediate layer is exposed. The aluminum electrode layer and the copper electrode layer constitute an asymmetric metal electrode. The filter paper intermediate layer is coated with a sensitive material, which is a potassium chloride-modified h-C3N4 / PVA composite material.

2. The electric field-enhanced self-powered humidity sensor according to claim 1, characterized in that, The filter paper is water-based and porous, with a pore size of 20-25 μm. The potassium chloride-modified h-C3N4 particles have a particle size of 200-300 nm, and the aluminum electrode layer and copper electrode layer have a thickness of 50-65 μm.

3. A method for fabricating an electric field-enhanced self-powered humidity sensor as described in any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Preparation of potassium chloride modified h-C3N4 material; (2) Potassium chloride modified h-C3N4 material was mixed with PVA to prepare potassium chloride modified h-C3N4 / PVA composite material; (3) The filter paper was impregnated with potassium chloride-modified h-C3N4 / PVA composite material and dried to obtain the modified filter paper; (4) Aluminum electrodes and copper electrodes are respectively covered on the upper and lower surfaces of the modified filter paper to obtain a humidity sensor.

4. The method for fabricating an electric field-enhanced self-powered humidity sensor according to claim 3, characterized in that, The specific steps (1) include: grinding and mixing NH4SCN and KCl, and then calcining at 500~600℃; dialyzing the calcined powder in a dialysis bag and vacuum drying to obtain potassium chloride modified h-C3N4; adding PVA particles to potassium chloride modified h-C3N4 to obtain potassium chloride modified h-C3N4 / PVA composite material.

5. The method for fabricating an electric field-enhanced self-powered humidity sensor according to claim 4, characterized in that, The weight ratio of NH4SCN to KCl is 8~12:

1.

6. The method for fabricating an electric field-enhanced self-powered humidity sensor according to claim 3, characterized in that, Step (2) specifically includes: adding potassium chloride-modified h-C3N4 material and PVA to deionized water and ultrasonically dispersing for 5-10 minutes to obtain potassium chloride-modified h-C3N4 / PVA composite material.

7. The method for fabricating an electric field-enhanced self-powered humidity sensor according to claim 6, characterized in that, The mass ratio of the potassium chloride-modified h-C3N4 material to PVA is 1~2:1~2.

8. The method for fabricating an electric field-enhanced self-powered humidity sensor according to claim 6, characterized in that, The specific steps (3) include: immersing the filter paper in potassium chloride-modified h-C3N4 / PVA composite material for 45-75 minutes, then drying it at 60-70°C, repeating the immersion-drying process 3-4 times to obtain the modified filter paper.

9. The application of the electric field-enhanced self-powered humidity sensor as described in any one of claims 1 to 2 in real-time monitoring of moisture information.

10. The application of the electric field-enhanced self-powered humidity sensor as described in any one of claims 1 to 2 in the manufacture of non-contact switches, non-contact keyboards, and / or respiratory disease monitoring devices.

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