Flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor and preparation method thereof

Abstract

The present invention belongs to the fields of energy harvesting technology, sensitive electronics and composite nanomaterial technology, and relates to a humidity sensor. Specifically, a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor and a preparation method thereof are provided. The present invention arranges a positive electrode and a negative electrode on the upper surface of a flexible substrate, and forms a sensitive channel between the two, and then fills the channel with a MXene nanosheet / acidic mucopolysaccharide composite material as a sensitive active layer; after adsorbing water molecules on the sensitive active layer, ionization generates positive and negative ions, thereby generating an oxidation-reduction reaction at the positive and negative electrodes, realizing a primary cell working mechanism, and then realizing self-powered humidity detection, that is, spontaneously generating a voltage signal in a humidity environment without any additional external driving force; and the present invention can achieve a wide detection range (10.9%-91.5% RH), fast response (response time 11.7s) and fast recovery (recovery time 2.8s), and has good flexibility.

Description

Technical Field

[0001] The present invention belongs to the fields of energy harvesting technology, sensitive electronics and composite nanomaterial technology, and relates to a humidity sensor. Specifically, a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor and a preparation method thereof are provided. Background Art

[0002] Humidity sensors are primarily used to measure changes in atmospheric humidity. They play an increasingly important, even indispensable, role in warehousing, grain and food mildew prevention, greenhouse cultivation, environmental monitoring, instrumentation and electrical equipment, transportation, meteorology, and missile and rocket storage. Traditional humidity sensors primarily include resistive, capacitive, and mass-sensitive types, all of which require an external power supply. Rising energy consumption and heightened environmental awareness are driving a stronger demand for green and renewable energy. Combining advanced energy production technologies with sensors to create self-powered systems is a key development direction for future electronic products. This not only addresses the limitations of green energy availability but also enables electronic products to operate independently and sustainably without the need for external charging.

[0003] In recent years, researchers have combined advanced energy generation technologies based on triboelectricity, piezoelectricity, or photovoltaics with sensing technologies to achieve self-powered humidity detection. For example, patent publication CN115112715A discloses a flexible, self-powered humidity sensor and its preparation method. This device is a piezoelectric humidity sensor. It uses a porous piezoelectric composite film made from piezoelectric polymers and nanomaterials. This porous piezoelectric composite film is then assembled with flexible electrodes with micron-sized pores to form a sandwich-structured, self-powered humidity sensor. When pressure is applied, the piezoelectric humidity sensor generates a voltage signal. As humidity increases, the voltage output gradually decreases, achieving humidity sensing. Although piezoelectric humidity sensors can output a voltage signal, they still require additional pressure, meaning they require external energy to operate. Unlike triboelectric and piezoelectric sensors, humidity sensors based on a galvanic cell mechanism can be directly driven by water molecules, outputting a voltage signal and achieving both humidity sensing and energy output. However, currently available humidity sensors of this type still face challenges in achieving a wide detection range, fast response, and flexibility. Summary of the Invention

[0004] The purpose of the present invention is to address the many problems existing in existing humidity sensors and provide a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor and a preparation method thereof; based on the excellent conductivity of MXene materials, the hydrophilic properties and mechanical strength of polysaccharide organic matter, and the three-dimensional nanostructure formed by the coupling of the two, the present invention obtains a MXene nanosheet / acidic mucopolysaccharide composite material as a sensitive active layer, and water molecules are adsorbed on the sensitive active layer and ionized to produce positive and negative ions, thereby causing redox reactions at the positive and negative electrodes, and then outputting a voltage signal to achieve self-powered humidity detection; and the present invention has the advantages of simple device structure, low cost, and high biocompatibility, providing a new approach for the development of high-performance, low-cost self-powered humidity sensing systems.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor comprises: a flexible substrate 1, a positive electrode 2, a negative electrode 3, and a sensitive active layer 4; the sensor is characterized in that the positive electrode and the negative electrode are arranged on the upper surface of the flexible substrate, and a channel is formed between the positive electrode and the negative electrode, and the sensitive active layer is filled in the channel. After the sensitive active layer adsorbs water molecules, it ionizes positive and negative ions, forming a potential difference between the positive and negative electrodes; the sensitive active layer adopts a MXene nanosheet / acidic mucopolysaccharide composite material.

[0007] Furthermore, the width of the channel is 0.1-1 mm.

[0008] Furthermore, the MXene nanosheets are made of Nb2CT x Nanosheets, Ti3C2T x Nanosheets or Ti2CT x Nanosheets, where T x Represents a terminal functional group.

[0009] Furthermore, the acidic mucopolysaccharide is hyaluronic acid.

[0010] Furthermore, the positive electrode is made of graphite, magnesium, manganese, iron, nickel, lead, copper, silver, platinum or gold, and the negative electrode is made of lithium, aluminum, manganese, zinc, cadmium or iron.

[0011] Furthermore, the flexible substrate is made of polyimide (PI), polyethylene terephthalate (PET) or polyurethane (PU).

[0012] The preparation method of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor is characterized by comprising the following steps:

[0013] Step 1: vacuum plasma cleaning the flexible substrate, and fabricating a positive electrode and a negative electrode on the cleaned flexible substrate;

[0014] Step 2: preparing a MXene nanosheet dispersion and an acidic mucopolysaccharide dispersion respectively, and then mixing the two at a mass ratio of 2:1 to obtain a flexible MXene / acidic mucopolysaccharide composite material dispersion;

[0015] Step 3: Deposit the flexible MXene / acidic mucopolysaccharide composite material in the channel between the positive electrode and the negative electrode to form a sensitive active layer; then dry it and remove the electrodes to obtain a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor.

[0016] Furthermore, in step 2, the preparation method of the MXene nanosheet dispersion includes etching with hydrofluoric acid (HF) or an indirect solution that can generate HF; then, intercalation is performed using an organic macromolecular base solution such as tetramethylammonium hydroxide (TMAOH), tetrabutylammonium hydroxide (TBAOH), tetrapropylammonium hydroxide (TPAOH), dimethyl sulfoxide (DMSO), etc.

[0017] Furthermore, in step 2, a flexible MXene / acidic mucopolysaccharide composite dispersion is prepared by mechanical mixing, in situ growth and other processes.

[0018] Furthermore, in step 3, the deposition process includes: coating with a paint pen, spraying or dripping process to prepare a single layer or multilayer film.

[0019] Based on the above technical solution, the beneficial effects of the present invention are:

[0020] 1. The present invention proposes a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor, in which a positive electrode and a negative electrode are arranged on the upper surface of a flexible substrate, and a sensitive channel is formed between the two. Then, a MXene nanosheet / acidic mucopolysaccharide composite material is filled in the channel as a sensitive active layer, thereby preparing a device with dual functions of humidity sensing and power generation. For the MXene nanosheet / acidic mucopolysaccharide composite material, based on the excellent conductivity of the MXene material, the hydrophilic properties and mechanical strength of the polysaccharide organic matter, and the three-dimensional nanostructure formed by the coupling of the two, the adsorption capacity and adsorption sites of the sensitive active layer for water molecules can be significantly enhanced. After the water molecules are adsorbed on the sensitive active layer, they are ionized to produce positive and negative ions, thereby causing redox reactions at the positive and negative electrodes, realizing the primary cell working mechanism, and further realizing self-powered humidity detection. That is, the voltage-type humidity sensor of the present invention does not require an additional external power supply and external driving force, and can spontaneously generate a voltage signal in a humidity environment, with the significant advantages of being green, environmentally friendly, energy-saving, and low power consumption.

[0021] 2. The flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor proposed in the present invention can achieve a wide detection range (10.9%-91.5% RH), fast response (response time 11.7s) and fast recovery (recovery time 2.8s), and has good flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor in the present invention.

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the MXene nanosheet / acidic mucopolysaccharide composite material in an embodiment of the present invention.

[0024] Figure 3 This is a voltage-relative humidity (RH) curve of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor in an embodiment of the present invention.

[0025] Figure 4 This is a response-recovery time curve of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor in an embodiment of the present invention.

[0026] Figure 5 This is a repeatability curve diagram of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings.

[0028] Example 1

[0029] This embodiment provides a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor, the structure of which is as follows: Figure 1 As shown, it specifically includes: a flexible substrate 1, a positive electrode 2, a negative electrode 3 and a sensitive active layer 4, wherein the positive electrode and the negative electrode are arranged on the upper surface of the flexible substrate, and a channel is formed between the positive electrode and the negative electrode, and the sensitive active layer is filled in the channel. After the active layer adsorbs water molecules, it ionizes positive and negative ions, forming a potential difference at the positive and negative electrodes.

[0030] In this embodiment, PI is used as a flexible substrate, Zn foil is used as a negative electrode, Cu tape is used as a positive electrode, and MXene nanosheets / acidic mucopolysaccharide composite material is used as a sensitive active layer. More specifically, MXene nanosheets are made of Nb2CT x The nanosheets and acidic mucopolysaccharide are made of hyaluronic acid.

[0031] This embodiment also provides a method for preparing the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor, comprising the following steps:

[0032] Step 1: Pre-clean the PI flexible substrate using a vacuum plasma cleaning device, and attach a positive electrode and a negative electrode to the left and right sides of the upper surface of the flexible substrate, respectively, and control the width of the sensitive channel between the positive electrode and the negative electrode to be less than 1 mm;

[0033] Step 2: Configure Nb2CT x Aqueous solution: 2 g of Nb2AlC powder was weighed using an electronic balance, and 30 mL of HF solution was measured using a pipette. The two were evenly mixed and placed in a beaker for etching for 72 h. The mixed liquid was then centrifuged to obtain a black precipitate. The precipitate was then intercalated with TMAOH solution for 48 h and then centrifuged and washed for later use.

[0034] Step 3. Configure Nb2CT x 35 mg of hyaluronic acid powder was weighed using an electronic balance, and 5 mL of 14 mg / mL Nb2CT was measured using a pipette. x Nanosheet aqueous solution, mix the two and stir evenly for later use.

[0035] Step 4: Prepare Nb2CT on the substrate by brush coating process x / hyaluronic acid composite active layer, which was dried for 12 hours to obtain a Nb2CT-based x / hyaluronic acid composite material voltage-type humidity sensor.

[0036] Based on the above preparation process, Nb2CT x The SEM image of the composite sensitive active layer (film) of hyaluronic acid was shown in FIG. Figure 2 As shown in the figure, Nb2CT x After coupling with hyaluronic acid, the composite material exhibits a three-dimensional nanostructure, providing abundant adsorption sites for water molecules; Nb2CT x The excellent conductivity of the nanosheets is beneficial to improving the output power of the device. x The abundant hydrophilic groups on the surface of the nanosheets further promote the adsorption of water molecules; in addition, hyaluronic acid, which has soft material properties, can enhance the adhesion of MXene nanosheets on the substrate and the flexibility of the sensitive active layer.

[0037] The performance of the prepared flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor was tested according to the commonly used method. Specifically, the voltage signal of the device was collected using a Keithley 6500 source meter. The relative humidity (RH) environment was obtained by the bubbling method and calibrated by a high-precision humidity sensor. The relative humidity included: 0%, 10.9%, 28.8%, 51.9%, 72.0% and 91.5%. Figure 3 The figure shows the voltage-relative humidity (RH) curve of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor. It can be seen from the figure that as the humidity increases, the voltage output of the sensor gradually increases and exhibits excellent adsorption-desorption characteristics; Figure 4 The following is the response-recovery time curve of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor. It can be seen from the figure that thanks to Nb2CT x After coupling the three-dimensional structure and surface groups of hyaluronic acid, the sensor exhibits fast response time and recovery time. For example, at 28.8% RH, the response time of the sensor is 11.7s, the recovery time is 2.8s, and the sensor has no obvious baseline drift. Figure 5 The figure shows the repeatability curve of the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor. It can be seen from the figure that the composite material-based voltage-type humidity sensor has good repeatability.

[0038] Example 2

[0039] This embodiment provides a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor, which has the same structure as that of Example 1, except that PET is used as the flexible substrate, Zn foil is used as the negative electrode, graphite is used as the positive electrode, and the MXene nanosheets are Ti3C2T x The nanosheets and acidic mucopolysaccharide are made of hyaluronic acid.

[0040] This embodiment also provides a method for preparing the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor, comprising the following steps:

[0041] Step 1: Pre-clean the PET flexible substrate using a vacuum plasma cleaning device, and attach a positive electrode and a negative electrode to the left and right sides of the upper surface of the flexible substrate, respectively, and control the width of the sensitive channel between the positive electrode and the negative electrode to be less than 1 mm;

[0042] Step 2. Configure Ti3C2T x Aqueous solution: 2 g of Ti3AlC2 powder was weighed using an electronic balance, and 20 mL of HF solution was measured using a pipette. The two were evenly mixed and placed in a beaker for etching for 24 h. The mixed liquid was then centrifuged to obtain a black precipitate. The precipitate was then intercalated with TMAOH solution for 24 h and then centrifuged and washed for later use.

[0043] Step 3. Configure Ti3C2T x / hyaluronic acid composite material aqueous solution. 35 mg of hyaluronic acid powder was weighed using an electronic balance, and 5 mL of 14 mg / mL Ti3C2T x Nanosheet aqueous solution, mix the two and stir evenly for later use.

[0044] Step 4: Prepare Ti3C2T on the substrate by brush coating process x / hyaluronic acid composite active layer, which was dried for 12 hours to obtain a Ti3C2T x / hyaluronic acid composite material voltage-type humidity sensor.

[0045] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, may be combined in any way.

Claims

1. A flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor, comprising: A flexible substrate (1), a positive electrode (2), a negative electrode (3) and a sensitive active layer (4); characterized in that the positive electrode and the negative electrode are arranged on the upper surface of the flexible substrate, and a channel is formed between the positive electrode and the negative electrode, and the sensitive active layer is filled in the channel. The sensitive active layer adsorbs water molecules and ionizes positive and negative ions, forming a potential difference at the positive and negative electrodes; the sensitive active layer adopts a MXene nanosheet / acidic mucopolysaccharide composite material, and the acidic mucopolysaccharide adopts hyaluronic acid.

2. The flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 1, characterized in that: The width of the channel is 0.1-1 mm.

3. The flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 1, characterized in that: The MXene nanosheets are made of Nb2CT x Nanosheets, Ti3C2T x Nanosheets or Ti2CT x Nanosheets, where T x Represents a terminal functional group.

4. The flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 1, characterized in that: The positive electrode is made of graphite, magnesium, manganese, iron, nickel, lead, copper, silver, platinum or gold, and the negative electrode is made of lithium, aluminum, manganese, zinc, cadmium or iron.

5. The flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 1, characterized in that: The flexible substrate is made of polyimide (PI), polyethylene terephthalate (PET) or polyurethane (PU).

6. The method for preparing the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 1, characterized in that: The following steps are involved: Step 1: vacuum plasma cleaning the flexible substrate, and fabricating a positive electrode and a negative electrode on the cleaned flexible substrate; Step 2: preparing a MXene nanosheet dispersion and an acidic mucopolysaccharide dispersion respectively, and then mixing the two at a mass ratio of 2:1 to obtain a flexible MXene / acidic mucopolysaccharide composite material dispersion; Step 3: Deposit the flexible MXene / acidic mucopolysaccharide composite material in the channel between the positive electrode and the negative electrode to form a sensitive active layer; then dry it and remove the electrodes to obtain a flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor.

7. The method for preparing the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 6, characterized in that: In step 2, the preparation method of the MXene nanosheet dispersion includes: etching with hydrofluoric acid (HF) or an indirect solution that can generate HF; then, intercalation is performed using tetramethylammonium hydroxide (TMAOH), tetrabutylammonium hydroxide (TBAOH), tetrapropylammonium hydroxide (TPAOH), and dimethyl sulfoxide (DMSO).

8. The method for preparing the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 6, characterized in that: In step 2, a flexible MXene / acidic mucopolysaccharide composite dispersion is prepared by mechanical mixing and in situ growth process.

9. The method for preparing the flexible MXene composite acidic mucopolysaccharide-based voltage-type humidity sensor according to claim 6, characterized in that: In step 3, the deposition process includes: coating with a paint pen, spraying or dripping process to prepare a single layer or multilayer film.

Images