Asymmetric sandwich type self-driven humidity sensor

Abstract

The asymmetric sandwich type self-driven humidity sensor comprises a sensitive layer made of a cellulose metal salt compound, the upper side and the lower side of the sensitive layer are provided with a positive electrode and a negative electrode which are asymmetrically arranged, and the sensitive layer is partially exposed out of an electrode end which is not completely covered by the sensitive layer to form a humidity sensitive interface. The sensitive layer can be in contact with water molecules in the air, the sensitive layer adsorbs the water molecules and then ionizes positive and negative ions, oxidation-reduction reaction is carried out on the positive and negative electrodes, and therefore humidity sensitivity sensing and energy supply are carried out simultaneously and synergistically. 1, two electrodes are made into an asymmetric structure, one electrode is provided with a hollow pattern, so that a part of the sensitive layer is exposed in the air and is easier to contact with water molecules; 2, cellulose and metal salt are used as sensitive layer ions which are simple, easy to obtain and low in cost; and 3, the prepared humidity sensor can output voltage in a self-driven manner under the humidity condition, passive detection is realized, and the humidity sensor has the remarkable advantages of energy conservation and environmental protection.

Description

Technical Field

[0001] This invention relates to an asymmetric sandwich-type self-driven humidity sensor, belonging to the fields of sensitive electronics and composite materials technology. Background Technology

[0002] Humidity, as a crucial environmental indicator, requires strict control in various settings, including industrial production and daily life such as warehousing, greenhouse cultivation, instrumentation, and meteorology. Monitoring environmental humidity primarily relies on humidity sensors. As a key direction for the future development of electronic products, self-powered electronic devices can operate without external power, aligning with green development principles.

[0003] In recent years, research has emerged that combines power generation technologies based on triboelectricity, piezoelectricity, or photovoltaics with sensing technologies to achieve self-powered humidity detection. Humidity sensors based on triboelectric and piezoelectric principles rely on friction or applied pressure to output a voltage signal, still requiring external actuation. Self-powered humidity sensors based on the principle of galvanic cells, which directly utilize water molecules in the humidity environment to drive the sensor's output voltage, offer an advantage. Simple structure and fabrication process, along with low cost, are key challenges that self-powered humidity sensors need to address. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an asymmetric sandwich-type self-driven humidity sensor.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An asymmetric sandwich-type self-driven humidity sensor includes a sensitive layer made of a cellulose metal salt composite and positive and negative electrodes made of conductive material. The positive and negative electrodes are asymmetrically arranged and placed on the upper and lower sides of the sensitive layer, respectively. A portion of the sensitive layer has partially exposed electrodes, forming a humidity-sensitive interface that can contact water molecules in the air. After adsorbing water molecules, the sensitive layer ionizes into positive and negative ions, which undergo redox reactions at the positive and negative electrodes. This allows for simultaneous and coordinated humidity sensing and power supply. The manufacturing steps are as follows: I. Preparation of humidity-sensitive composite materials; A certain amount of metal salt is added to a cellulose aqueous solution and the metal salt is dissolved by ultrasonication to form a transparent and uniform cellulose metal salt complex. 2. The prepared humidity-sensitive composite material is deposited on the surface of any electrode and dried to form a sensitive layer film; Third, attach another asymmetrical electrode to the other side of the sensitive layer film, making that side have several moisture-sensitive interfaces that expose the inner sensitive layer.

[0006] The metal salt is one or more of LiCl, MgCl2, KCl, NaCl, Mg(NO3)2, and KNO3.

[0007] The cellulose aqueous solution is any one of methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, or carboxymethylcellulose.

[0008] The positive electrode is made of any one of iron, nickel, lead, copper, silver, platinum or gold, and the negative electrode is made of any one of copper, aluminum, zinc or iron.

[0009] The positive and negative electrodes can be made of conductive tape, conductive fiber, or conductive fabric of different materials, or they can be obtained by printing or printing processes using conductive ink of different materials.

[0010] In step two, a mold with a certain depth of groove can be prepared, the humidity-sensitive composite material can be filled into the mold, and the mold can be removed by drying.

[0011] 7. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: the sensitive layer is prepared by drop coating or spray coating in step two.

[0012] 8. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: the positive and negative electrodes have an asymmetric structure, wherein the upper electrode is a hollow electrode, which is placed on the upper side of the sensitive layer and does not completely cover the sensitive layer.

[0013] The beneficial effects of this invention are: 1. The two electrodes are made into an asymmetrical structure, with one electrode not completely covering the sensitive layer. This exposes part of the sensitive layer to the air without increasing the sensor area, making it easier for it to come into contact with water molecules. 2. Using cellulose and metal salts as sensitive layer ions is simple, readily available, and inexpensive; 3. The prepared humidity sensor can self-drive the output voltage under humidity conditions to achieve passive detection, which has significant advantages of energy saving and environmental protection; 4. The self-driven humidity sensor prepared can be used for multiple functions such as environmental humidity detection, soil humidity detection, diaper humidity monitoring, non-contact distance detection, and respiratory rate and type detection. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the sensor structure. 1 and 3 are the positive and negative electrodes, and 2 is the sensitive layer.

[0015] Figure 2 This is the result of the sensor being used for respiratory rate detection.

[0016] Figure 3This is the result of using the humidity sensor for non-contact distance detection. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention discloses an asymmetric sandwich-type self-driven humidity sensor, comprising a sensitive layer made of a cellulose metal salt composite. The sensitive layer has asymmetrically arranged positive and negative electrodes on its upper and lower sides, with one end of the sensitive layer exposed to form a humidity-sensitive interface that can contact water molecules in the air. After adsorbing water molecules, the sensitive layer ionizes into positive and negative ions, which undergo redox reactions at the positive and negative electrodes, thereby achieving simultaneous and coordinated humidity sensing and power supply. The fabrication steps are as follows: I. Preparation of humidity-sensitive composite materials; The metal salt is one or more of LiCl, MgCl2, KCl, NaCl, Mg(NO3)2, and KNO3.

[0019] The cellulose aqueous solution is any one of methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, or carboxymethylcellulose.

[0020] A certain amount of metal salt is added to a cellulose aqueous solution and the metal salt is dissolved by ultrasonication to form a transparent and uniform cellulose metal salt complex. The positive electrode is made of any one of iron, nickel, lead, copper, silver, platinum or gold, and the negative electrode is made of any one of copper, aluminum, zinc or iron.

[0021] 2. Deposit the prepared humidity-sensitive composite material on the surface of any one of the electrodes; 3. Drying: Dry the obtained sample in an oven at 60℃; Fourth, attach another asymmetrical electrode to the other side of the dried sample, making this side have several humidity-sensitive interfaces that expose the internal sensitive layer. The humidity-sensitive interfaces are used for the interaction between the sensitive layer and water molecules in the air, for the permeation, adsorption and desorption of water molecules. After the sensitive layer adsorbs water molecules, it ionizes into positive and negative ions, which undergo redox reactions at the positive and negative electrodes, and output voltage from the positive and negative electrodes. Due to the piezoelectric effect, the external force applied to the sensitive layer forms electromechanical coupling, thereby changing the dielectric constant caused by the adsorption of water molecules, which modulates the piezoelectric output signal. Therefore, the concentration of external water molecules can be inferred from the magnitude of the piezoelectric output, realizing self-driven humidity detection.

[0022] Example 1 I. Preparation of Humidity-Sensitive Composite Materials 0.5 mol / L LiCl and 0.3 mol / L NaCl were added to a 1 wt% aqueous solution of carboxymethyl cellulose with a viscosity of 2500–4500 mPa·s, and the solution was further dissolved and dispersed uniformly by ultrasonication.

[0023] II. Fabrication of a flexible humidity sensor 1) Embed nickel conductive tape into a mold of the same width, wherein the mold is drawn using a drawing tool and then 3D printed; 2) Drop the mixed solution into the mold until the liquid level is about 3 mm high, so as to form a sensitive layer of a certain relative thickness; 3) Dry the obtained sample in a drying oven at 60℃ for 20-30 h; 4) After removing the dried sample, attach a layer of copper conductive tape with a hollowed-out pattern to the sensitive layer to obtain the humidity sensor.

[0024] The prepared carboxymethyl cellulose metal salt composite humidity sensor exhibits self-driven humidity response performance. Figure 1 This is a schematic diagram of the sensor structure. Figure 2 The image shows the results of detecting human respiratory rate. Figure 3 This is the result of non-contact distance detection.

[0025] The embodiments should not be regarded as limitations on the present invention, but any improvements made based on the spirit of the present invention should be within the protection scope of the present invention.

Claims

1. An asymmetric sandwich type self-driven humidity sensor, characterized by: It comprises a sensitive layer made of a cellulose metal salt composite and positive and negative electrodes made of conductive material, which are asymmetrically arranged and placed on the upper and lower sides of the sensitive layer, respectively. A portion of the sensitive layer has its partially exposed electrodes forming a humidity-sensitive interface that can contact water molecules in the air. After adsorbing water molecules, the sensitive layer ionizes to release positive and negative ions, which then undergo redox reactions at the positive and negative electrodes. This allows for simultaneous and coordinated humidity sensing and power supply. The manufacturing steps are as follows: I. Preparation of humidity-sensitive composite materials; A certain amount of metal salt is added to a cellulose aqueous solution and the metal salt is dissolved by ultrasonication to form a transparent and uniform cellulose metal salt complex.

2. The prepared humidity-sensitive composite material is deposited on the surface of any electrode and dried to form a sensitive layer film; Third, attach another asymmetrical electrode to the other side of the sensitive layer film, making that side have several moisture-sensitive interfaces that expose the inner sensitive layer.

2. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: The metal salt is one or more of LiCl, MgCl2, KCl, NaCl, Mg(NO3)2, and KNO3.

3. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: The cellulose aqueous solution is any one of methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, or carboxymethylcellulose.

4. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: The positive electrode is made of any one of iron, nickel, lead, copper, silver, platinum or gold, and the negative electrode is made of any one of copper, aluminum, zinc or iron.

5. The method for fabricating an asymmetric sandwich-type self-driven multifunctional humidity sensor according to claim 1, characterized in that: The positive and negative electrodes can be made of conductive tape, conductive fiber, or conductive fabric of different materials, or they can be obtained by printing or printing processes using conductive ink of different materials.

6. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: In step two, a mold with a certain depth of groove can be prepared, the humidity-sensitive composite material can be filled into the mold, and the mold can be removed by drying.

7. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: In step two, the sensitive layer is prepared using drop-coating or spray-coating methods.

8. The asymmetric sandwich-type self-driven humidity sensor according to claim 1, characterized in that: The positive and negative electrodes have an asymmetrical structure, with the upper electrode being a hollow electrode that is placed on top of the sensitive layer and does not completely cover the sensitive layer.

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