A stretchable, self-healing, breathable humidity sensor and a preparation method thereof

Abstract

The application belongs to the technical field of sensors, and provides a stretchable, self-repairable and breathable humidity sensor and a preparation method thereof.The humidity sensor is mainly prepared by using a humidity-sensitive material and an electrode.The humidity-sensitive material is a physically cross-linked organic hydrogel, which comprises a solvent system and a degradable gel matrix in a certain ratio.The degradable gel matrix is one or more of polyvinyl alcohol, gelatin, carrageenan, alginate and agar.The degradable gel matrix has the properties of degradability, flexibility, stretchability and breathability, and can well adapt to the deformation of the skin, and can be used to prepare wearable electronic devices.In addition, the organic hydrogel contains a large number of hydrophilic groups, and can realize good humidity sensing, high sensitivity and wide monitoring range.The physically cross-linked organic hydrogel can realize self-repairing, so that the device can realize long-term and repeatable work, and can be widely applied to humidity monitoring.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, and more particularly to a stretchable, self-healing and breathable humidity sensor and a preparation method thereof. BACKGROUND

[0002] Humidity is an important environmental parameter, and accurate humidity monitoring can well guarantee the comfort of human life, and has important practical use in home, weather, food and industrial and agricultural production. More importantly, exhaled gas and human skin are obvious humidity sources, so the measurement of humidity can also be used for the characterization of some human physiological signals, such as respiratory rate and skin moisture, which can assist in the diagnosis, prevention and rehabilitation of diseases and non-contact human-machine contact, which means that it is quite necessary to develop a wearable and flexible humidity sensor. At present, the mainstream humidity sensors are mainly made of materials such as graphene and its derivatives, metal oxides, transition metal sulfides, porous ceramics and conductive polymers, however, although these humidity sensor devices have good sensing performance, they are all rigid and non-stretchable, lack of energy dissipation mechanism inside the material, and do not have self-healing property, and are easily damaged irreversibly and permanently under external force. Even after integration with a flexible substrate, long-term repeated deformation and large-scale stretching will still cause irreversible damage to the device, and the degraded electronic devices will eventually be discarded, which will seriously lead to further accumulation of electronic waste and cause environmental pollution. Therefore, it is urgent to develop a flexible, stretchable, self-healing, breathable and degradable humidity sensor. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a stretchable, self-healing and breathable humidity sensor and a preparation method thereof, the humidity sensor provided by the present application includes a humidity-sensitive material and an electrode, has high humidity responsiveness, a wide monitoring range (11-98% RH), flexibility, stretchability, self-healing property, a degradable humidity-sensitive material and good breathability.

[0004] A first aspect of the present application provides a stretchable, self-healing and breathable humidity sensor.

[0005] In particular, a humidity sensor includes a humidity-sensitive material and an electrode;

[0006] The humidity-sensitive material is a physically cross-linked organic hydrogel;

[0007] The physically cross-linked organic hydrogel includes a solvent system and a degradable gel matrix;

[0008] The degradable gel matrix is one or more of polyvinyl alcohol, gelatin, carrageenan, alginate and agar;

[0009] The mass of the degradable gel matrix is 10-30% of the mass of the solvent system.

[0010] The present application mainly uses a specific content of physically cross-linked organic hydrogel as the humidity-sensitive material of the humidity sensor. The physically cross-linked organic hydrogel is composed of a degradable gel matrix and a solvent system in a certain ratio. The degradable gel matrix is selected from one or more of polyvinyl alcohol (PVA), gelatin, carrageenan, alginate, and agar. Not only does it have degradability, but the key is that these degradable organic hydrogels contain a large number of hydrophilic groups, including at least one of hydroxyl, carboxyl, and amino groups, which can serve as water molecule adsorption sites and greatly improve the humidity sensitivity of the material. When the humidity in the environment increases, water molecules will adsorb water in the gel network, thereby increasing the water content, leading to an increase in electrical conductivity and capacitance, thereby realizing humidity sensing in both electrical conductivity and capacitance modes, and giving the humidity sensor good responsiveness and excellent humidity sensing performance, including high sensitivity and wide monitoring range. Moreover, the organic hydrogel forms a physically cross-linked structure through electrostatic force, hydrogen bonding, hydrophobic interaction, and other rich non-covalent interactions. This reversible cross-linked structure enables the hydrogel to self-repair or remodel after suffering different degrees of damage, such as when the gel is worn or broken, it can be repaired by local heating, etc., to achieve self-repairing of mechanical and electrical properties, so that the device can work for a long time and repeatedly, and it is also beneficial to avoid the generation of electronic waste. In addition, the organic hydrogel has good intrinsic flexibility and stretchability, can better adapt to the deformation of the skin, and also has certain air permeability, which can be well used to prepare wearable electronic devices. The mass ratio of the solvent system and the degradable gel matrix will ultimately affect the quality of the synthesized organic hydrogel, the humidity detection performance, and the application. When the gel matrix content is too low, the strength of the organic hydrogel will be too low. When the gel matrix content is too high, the precursor solution viscosity is too high, which is not conducive to the formation of the organic hydrogel.

[0011] Preferably, the humidity-sensitive material and the electrode are combined in a manner of adhesion or suture.

[0012] Preferably, the mass of the degradable gel matrix is 10-15% of the mass of the solvent system.

[0013] Preferably, the humidity-sensitive material further comprises a nano-filler. In order to further improve its mechanical properties, a certain content of high-strength nano-filler is added, which helps to achieve the toughening of the gel.

[0014] Preferably, the mass of the nano-filler is 0-5% of the mass of the solvent system.

[0015] More preferably, the mass of the nano-filler is 1-3% of the mass of the solvent system.

[0016] Preferably, the nanofiller is one or several of cellulose nanofiber (CNF), carbon nanotube, silver nanowire, nanoclay.

[0017] More preferably, the nanofiller is cellulose nanofiber.

[0018] Preferably, the cellulose nanofiber has a diameter of 10-50 nm and a length of 100-500 nm.

[0019] Preferably, the nanoclay has an average particle size of 1-1000 nm.

[0020] More preferably, the nanoclay has an average particle size of 1-100 nm.

[0021] Preferably, the solvent system is a dual solvent system.

[0022] Preferably, the dual solvent system comprises water and an organic solvent. Generally, the stability of the hydrogel is weak, and long-term placement is prone to dehydration and drying, which is not conducive to long-term use. Therefore, the present application adopts a dual solvent system of water and an organic solvent, which can improve the dry resistance of the humidity-sensitive material, prevent performance deterioration caused by water loss, and give the organic hydrogel long-term stability. In addition, the internal organic hydrogel can conduct electricity by proton migration, and does not need to introduce additional ionic salt, which is friendly to the environment and human health.

[0023] Preferably, the organic solvent is a polyol.

[0024] Preferably, the polyol is one or several of glycerol, ethylene glycol, and sorbitol.

[0025] Preferably, the thickness of the humidity-sensitive material is 1-1000 μm.

[0026] Preferably, the humidity-sensitive material is a thin film structure. Since wearable electronic devices are in direct contact with the human body, the requirement for air permeability is high. The present application uses a thin film-shaped organic hydrogel to prepare a humidity sensor. The thin film structure not only has a simple preparation process and low cost, but also helps to improve the air permeability of the organic hydrogel. When attached to the skin for a long time, it will not cause the accumulation of sweat, and will not affect the response to humidity, which has obvious advantages in the preparation of wearable humidity sensors.

[0027] More preferably, the thickness of the thin film structure is 1-100 μm. The transparency increases with the decrease of the thickness of the humidity-sensitive material. With the decrease of the thickness, more adsorption sites are exposed, which is conducive to further improving the humidity responsiveness.

[0028] The second aspect of the present application provides a preparation method of a stretchable, self-repairable and breathable humidity sensor.

[0029] A preparation method of a stretchable, self-repairable, breathable humidity sensor, comprising the following steps:

[0030] The humidity-sensitive material and the electrode are combined in a manner of lamination or sewing, that is, the humidity sensor is prepared.

[0031] Preferably, the preparation method of the humidity-sensitive material comprises the following steps:

[0032] One or more of polyvinyl alcohol, gelatin, carrageenan, alginate and agar are dissolved in a solvent, a precursor solution is prepared by heating, and then physical crosslinking is performed on a substrate by spin coating to prepare the humidity-sensitive material.

[0033] Preferably, the heating temperature is 90-110°C, and the heating time is 2-6 hours.

[0034] Preferably, the spin coating speed is 500-3500 rpm. The transparency and thickness of the organic hydrogel are controlled by controlling the spin coating speed.

[0035] More preferably, the spin coating speed is 1500-2500 rpm.

[0036] The third aspect of the present application provides a stretchable, self-repairable, breathable humidity sensor.

[0037] A stretchable, self-repairable, breathable humidity sensor in the field of wearable electronic devices.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] (1) The present application mainly uses a humidity-sensitive material and an electrode to form a humidity sensor. The humidity-sensitive material is a physically crosslinked organic hydrogel, which includes a solvent system and a degradable gel matrix in a specific ratio to ensure the morphology and quality of the humidity-sensitive material. The gel matrix is selected from one or more of polyvinyl alcohol, gelatin, carrageenan, alginate and agar. The humidity-sensitive material not only has degradability, flexibility and stretchability, but also contains a large number of hydrophilic groups, including at least one of hydroxyl, carboxyl and amino groups, which can achieve good humidity sensing, high responsiveness, high sensitivity and wide monitoring range (11-98% RH). The physically crosslinked organic hydrogel can realize self-repairing or reshaping, so that the device can realize long-term and repeatable work, and also has certain breathability.

[0040] (2) The humidity sensor of the present application has good flexibility, stretchability, repairability and breathability, and can well adapt to the deformation of the skin. It can be used to prepare wearable electronic devices and is widely used in humidity monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 Structure diagram of humidity sensor prepared for example 7 of the present application;

[0042] Figure 2 Process flow chart of preparation of organic hydrogel film prepared for example 1 of the present application;

[0043] Figure 3 Optical micrographs of organic hydrogels prepared for examples 1-6 of the present application at different spin-coating speeds;

[0044] Figure 4 Heating repair after cutting and destroying the organic hydrogel prepared for example 11 of the present application;

[0045] Figure 5 Test results of degradability, anti-freezing property of organic hydrogel prepared for example 1 of the present application, and transparency of organic hydrogels prepared for examples 1, 2, 4 of the present application;

[0046] Figure 6 Stress-strain curves of organic hydrogel films prepared for examples 1, 3, 6 of the present application;

[0047] Figure 7 Moisture mass loss of water in bottles with bottle opening covered by organic hydrogel films prepared for examples 3, 6 of the present application and directly open bottles;

[0048] Figure 8 Conductance and capacitance response of humidity sensors prepared for examples 1, 3, 4 of the present application under different humidity;

[0049] Figure 9 Response of humidity sensor in example 7 of the present application to 98% RH at different times;

[0050] Figure 10 Response of humidity sensors of examples 3, 8, 9, 10 of the present application to different humidity;

[0051] Figure 11 Response of humidity sensors of examples 3, 11 of the present application to different humidity;

[0052] Figure 12 Application of humidity sensor prepared for example 7 of the present application in breath, sneeze, and finger proximity tests. DETAILED DESCRIPTION

[0053] In order to make the skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0054] The raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0055] Example 1

[0056] A stretchable, self-healing, breathable humidity sensor, comprising a humidity-sensitive material and an electrode, the humidity-sensitive material and the electrode are combined in a conforming manner, the humidity-sensitive material is a physically cross-linked polyvinyl alcohol hydrogel, the physically cross-linked polyvinyl alcohol hydrogel comprises a solvent system (water and glycerol) and a degradable gel matrix (polyvinyl alcohol hydrogel), the mass of the degradable gel matrix is 15% of the mass of the solvent system.

[0057] The preparation method of the above-mentioned stretchable, self-healing, breathable humidity sensor, comprising the following steps:

[0058] (1) Mix glycerol and deionized water in a mass ratio of 1:1 as a solvent, add 1% of CNF (fiber diameter about 30 nm, length about 300 nm) to the solvent, ultrasonic dispersion, add 15% of PVA powder to the mixed solution, continuously stir at 100℃ for 5 hours, and finally obtain a uniform precursor solution;

[0059] (2) Ultrasonic cleaning and drying the aluminum substrate, and pre-adhering a circle of tape around it to facilitate the peeling of the finally formed organic hydrogel film;

[0060] (3) Place the treated aluminum sheet as a substrate on a spin coater, drop an appropriate amount of precursor solution on the upper surface of the substrate, and spin at a speed of 1500 rpm, thereby forming a uniform precursor solution film on the aluminum sheet;

[0061] (4) Place the substrate with the deposited precursor solution at room temperature for 12 hours, and finally obtain a physically cross-linked PVA-CNF organic hydrogel film, the film thickness is 123.39μm;

[0062] (5) Take the organic hydrogel film, cut it into a long strip, and take another two pieces of conductive tape, paste them on both ends of the gel with silver paste, and finally obtain a humidity sensor.

[0063] Example 2

[0064] The difference between this embodiment and Example 1 is that the spin coating speed in step (3) is 2000 rpm, and the PVA-CNF organic hydrogel film prepared has a film thickness of 97.31μm.

[0065] Example 3

[0066] The difference between this embodiment and embodiment 1 is that the spin-coating speed of step (3) is 2500 rpm, and the prepared PVA-CNF organic hydrogel film has a film thickness of 62.47 μm.

[0067] Embodiment 4

[0068] The difference between this embodiment and embodiment 1 is that the spin-coating speed of step (3) is 500 rpm, and the prepared PVA-CNF organic hydrogel film has a film thickness of 271.92 μm.

[0069] Embodiment 5

[0070] The difference between this embodiment and embodiment 1 is that the spin-coating speed of step (3) is 1000 rpm, and the prepared PVA-CNF organic hydrogel film has a film thickness of 231.89 μm.

[0071] Embodiment 6

[0072] The difference between this embodiment and embodiment 1 is that the spin-coating speed of step (3) is 3500 rpm, and the prepared PVA-CNF organic hydrogel film has a film thickness of 43.23 μm.

[0073] Embodiment 7

[0074] The difference between this embodiment and embodiment 1 is that the conductive tape in step (5) is stitched at both ends of the organic hydrogel by using silver wire.

[0075] Embodiment 8

[0076] The difference between this embodiment and embodiment 3 is that the humidity sensor in embodiment 3 is stretched, and the degree of stretching is 50% strain of the original length.

[0077] Embodiment 9

[0078] The difference between this embodiment and embodiment 3 is that the humidity sensor in embodiment 3 is stretched, and the degree of stretching is 100% strain of the original length.

[0079] Embodiment 10

[0080] The difference between this embodiment and embodiment 3 is that the humidity sensor in embodiment 3 is bent, and the bending angle is 180°.

[0081] Embodiment 11

[0082] The difference between this embodiment and embodiment 3 is that the humidity sensor prepared in embodiment 3 is cut, and the cut part is locally heated to a temperature of 64℃ for 5 s to perform self-repair.

[0083] Embodiment 12

[0084] The difference between this embodiment and embodiment 1 is that the mass of the polyvinyl alcohol hydrogel is 20% of the mass of the solvent system.

[0085] Example 13

[0086] The difference between this embodiment and embodiment 1 is that CNF is not contained.

[0087] Example 14

[0088] The difference between this embodiment and embodiment 1 is that the polyvinyl alcohol hydrogel in this embodiment is in the form of a block with a size of 2x4x1mm.

[0089] Comparative Example 1

[0090] The difference between this comparative example and embodiment 1 is that the physically cross-linked polyvinyl alcohol hydrogel in embodiment 1 is replaced by a chemically cross-linked polyacrylamide hydrogel. After the gel in this comparative example is cut and then subjected to local heat, an intact gel cannot be obtained, which proves that the chemically cross-linked polyacrylamide hydrogel does not have self-repairing performance.

[0091] Comparative Example 2

[0092] The difference between this comparative example and embodiment 1 is that the mass of the polyvinyl alcohol hydrogel is 35% of the mass of the solvent. The viscosity of the precursor solution of the hydrogel obtained in this comparative example is too high, and the flowability is poor. A thin film structure cannot be obtained by spin coating, and the obtained gel structure is irregular, which affects its response to humidity and cannot be well applied to measure humidity.

[0093] Comparative Example 3

[0094] The difference between this comparative example and embodiment 1 is that the mass of the polyvinyl alcohol hydrogel is 8% of the mass of the solvent. The content of the gel matrix in this comparative example is too low, which is not conducive to the formation of a tough gel, and the tensile property is too low.

[0095] Product effect test

[0096] Figure 1 is a structural schematic diagram of a humidity sensor prepared in embodiment 7 of the present application. As can be seen from the figure, the humidity sensor of the present application mainly comprises a physically cross-linked organic hydrogel film (PVA, CNF) containing a double solvent system (water H2O, glycerol Gly) and a conductive electrode, and has excellent flexibility and stretchability.

[0097] The film preparation process steps of the organic hydrogel in embodiment 1 of the present application are as follows Figure 2As shown, firstly, PVA and CNF are dissolved in a solvent system composed of water and glycerol (Gly), and heated to form a hydrogel precursor solution with a certain viscosity. Next, the precursor solution is spin-coated onto an aluminum substrate at a certain speed, leaving a uniform precursor solution of a certain thickness on the aluminum substrate. Finally, the substrate is allowed to stand to allow the precursor solution to gel, ultimately forming a physically cross-linked organic hydrogel film. Throughout the process, the substrate acts as a support, and applying a ring of adhesive tape around the aluminum sheet beforehand facilitates the peeling of the formed organic hydrogel film from the aluminum sheet.

[0098] Figure 3 Images (a)-(f) are optical micrographs of organic hydrogel films of different thicknesses obtained at different spin-coating speeds in Examples 4, 5, 1, 2, 3, and 6 of this invention, respectively. It can be seen that the thicknesses of the obtained organic hydrogel films are on the order of micrometers. The thicknesses of the organic hydrogel films obtained in Examples 1-3 are 123.39, 97.31, and 62.47 μm, respectively. The thicknesses of the organic hydrogel films obtained in Examples 4-6 are 271.92, 231.89, and 43.23 μm, respectively. However, in Example 12, due to the increased PVA content, the viscosity of the precursor solution was too high, resulting in a less uniform spin-coated film compared to Examples 1-6.

[0099] Figure 4 (a)-(c) represent the uncut organic hydrogel of Example 3, the cut organic hydrogel, and the heat-repaired organic hydrogel (i.e., the hydrogel of Example 11), respectively. Figure 4 As can be seen, after the organic hydrogel film of Example 3 was cut open, by putting the cut edges together and applying local heating, the broken hydrogel film would rejoin and become intact, proving that the organic hydrogel of the present invention has good self-healing properties.

[0100] Figure 5 (a) Characterization of the degradability of the organic hydrogel prepared in Example 1 of the present invention. Figure 5 (b) Characterization of the antifreeze properties of the organic hydrogel prepared in Example 1 of the present invention. Figure 5 (c) Characterization of the light transmittance of the organic hydrogels prepared in Examples 1, 2 and 4 of the present invention. Figure 5 (a) It can be seen that the organic hydrogel can be rapidly degraded after being placed at a high temperature of 64°C for 5 seconds. Differential scanning calorimetry (DSC) was used to test the organic hydrogel prepared in Example 1 of this invention, and the results are as follows: Figure 5 As shown in (b), the organic hydrogel has a freezing point below -120°C, exhibiting excellent freeze resistance. The transmittance of the material was tested using a UV-Vis spectrometer, and the results are as follows: Figure 5(c) shows that the transmittance of the organic hydrogel films prepared in Examples 1, 2, and 4 can reach 70%, 55%, and 35% in the visible light range, respectively, indicating that the decrease in film thickness is conducive to the improvement of transparency.

[0101] Figure 6 Fig. 6 is a stress-strain curve of the organic hydrogel films prepared in Examples 1, 3, and 6. As can be seen, as the thickness of the organic hydrogel decreases, the strain also decreases, but the organic hydrogel still has a more excellent tensile property than traditional rigid humidity-sensitive materials (such as humidity-sensitive ceramics, 0% tensile property).

[0102] Fig. 7 shows the water mass loss of the bottles covered with the organic hydrogel films prepared in Examples 3 and 6, and the bottles directly exposed to the air. Figure 7 As can be seen, the water mass loss of the bottles covered with the organic hydrogel films prepared in Examples 3 and 6 is almost the same as that of the bottles directly exposed to the air, indicating that the material has excellent air permeability.

[0103] Figure 8 (a) is a dynamic conductance response curve of the organic hydrogel films prepared in Examples 1, 3, and 4 to different humidity, Figure 8 (b) is a relationship curve of the conductance response of the organic hydrogel films prepared in Examples 1, 3, and 4 and the relative humidity, Figure 8 (c) is a dynamic capacitance response curve of the organic hydrogel films prepared in Examples 1, 3, and 4 to different humidity, Figure 8 (d) is a relationship curve of the capacitance response of the organic hydrogel films prepared in Examples 1, 3, and 4 and the relative humidity. When exposed to humidity, water molecules will be adsorbed and diffused on the surface of the gel, resulting in an increase in ion mobility, thereby causing a change in conductance. At the same time, water molecules have a larger dielectric constant, so the capacitance also changes accordingly, realizing humidity sensing in a dual-mode of conductance and capacitance. As can be seen, the humidity sensing performance of the organic hydrogel is closely related to its thickness. As can be seen from Figure 8 (a) and Figure 8 (b), when the thickness is 271.92 μm (Example 4), the conductance response to humidity is the lowest, while when the thickness is reduced to 62.47 μm (Example 3), the response to 98% RH reaches 25000%, which is highly responsive. The bulk organic hydrogel in Comparative Example 2 has extremely weak response to humidity. Among them Figure 8 where RH is the relative humidity, △G / G0 is the conductance response value, and △C / C0 is the capacitance response value. Figure 8 (a) and Figure 8The grey shaded part in (c) from left to right represents relative humidity of 98% RH, 75% RH, 59% RH, 43% RH, 22% RH respectively, and the white part represents relative humidity of 11% RH. The organic hydrogel film prepared in Example 13 can also be used for sensing humidity, but the mechanical performance is slightly worse than that of the organic hydrogel added with nanofillers. The above also proves that the humidity sensor of the present application can respond to humidity in the range of 11% RH to 98% RH, and the monitoring range is wide.

[0104] Figure 9 (a) is the change of response of the humidity sensor of Example 7 of the present application to 98% RH in the time period of 1-7 days, Figure 9 (b) is the change of response of the humidity sensor of Example 7 of the present application to 98% humidity in the time period of 1-120 days. It can be seen that the response of the humidity sensor to humidity in the time period of 7 days has almost no downward trend, and the humidity sensor still has good response to humidity in the subsequent time period of 120 days, which shows that the humidity sensor of the present application has excellent long-term stability.

[0105] Figure 10 (a) is the relationship curve of the conductance response of the humidity sensor in Examples 3, 8 and 9 of the present application and relative humidity, Figure 10 (b) is the relationship curve of the conductance response of the humidity sensor in Examples 3 and 10 of the present application and relative humidity. It can be seen that the humidity sensor of the present application can be stretched to a certain extent (100% strain) and bent (180°), and has good flexibility, and after being subjected to different degrees of stretching and bending deformation, the humidity sensor can still normally respond to humidity. The above results prove that the organic hydrogel prepared in the present application can normally work in different deformation states such as stretching or folding, and can resist external stress damage to a certain extent.

[0106] It can be seen from Figure 11 that the humidity sensor of Example 11 of the present application is cut, then locally heated and melted, and when the temperature decreases, the gel can be formed again, realizing self-repair. The above results not only prove that physical crosslinking occurs between the organic hydrogels prepared in the present application, but also prove that the humidity sensor of the present application after self-repair still maintains good humidity response.

[0107] Figure 12 (a) is the application of the humidity sensor prepared in Example 1 of the present application in breath monitoring, in which the black background represents normal breathing, and the white background represents suspended breathing; Figure 12 (b) is the application of the humidity sensor prepared in Example 1 of the present application in sneezing monitoring, Figure 12(c) is the application of the humidity sensor prepared in Example 1 of the present application in a finger proximity test, where the black background indicates that the finger is close to the film and the white background indicates that the finger is away from the film. The results show that Figure 12 The results show that the increase in conductance is caused by exhalation (the turning point where the curve rises and then falls indicates inhalation, humidity decrease, and vice versa), sneezing, and finger proximity (finger close means that the distance between the finger and the film is less than 1 cm, and finger away means that the distance between the finger and the film is greater than 1 cm), which proves that the humidity sensor prepared in Example 1 of the present application can accurately identify the breathing frequency, breathing pattern, sneezing, and the degree of finger proximity.

Claims

1. A humidity sensor, characterized in that, Includes humidity-sensitive materials and electrodes; The humidity-sensitive material is a physically cross-linked organic hydrogel; The physically cross-linked organic hydrogel includes a solvent system and a biodegradable gel matrix; The biodegradable gel matrix is ​​polyvinyl alcohol; The mass of the biodegradable gel matrix is ​​10-30% of the mass of the solvent system.

2. The humidity sensor according to claim 1, characterized in that, The humidity-sensitive material also includes nanofillers.

3. The humidity sensor according to claim 2, characterized in that, The nanofiller is one or more of cellulose nanofibers, carbon nanotubes, silver nanowires, and nanoclay.

4. The humidity sensor according to claim 1, characterized in that, The solvent system is a dual-solvent system.

5. The humidity sensor according to claim 4, characterized in that, The dual-solvent system includes water and an organic solvent.

6. The humidity sensor according to claim 5, characterized in that, The organic solvent is a polyol.

7. The humidity sensor according to claim 1, characterized in that, The humidity-sensitive material has a thin film structure.

8. A method for preparing a humidity sensor according to any one of claims 1-7, characterized in that, Includes the following steps: The humidity sensor is fabricated by bonding or sewing together the humidity-sensitive material and the electrode.

9. The application of the humidity sensor according to any one of claims 1-7 in the field of humidity monitoring.

10. A wearable humidity sensing electronic device, characterized in that, Includes the humidity sensor described in any one of claims 1-7.

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