A photoexcited flexible room temperature gas sensor, its fabrication method and application

Abstract

This invention discloses a photoexcited flexible room-temperature gas sensor, its fabrication method, and its applications, belonging to the field of gas sensor technology. The sensor comprises a flexible gas-sensitive material layer, a flexible electrode layer, and a flexible photoexcitation layer, with the flexible electrode layer serving as the intermediate layer, forming a flexible photo-electric coupling sandwich structure. The flexible gas-sensitive material layer is a self-adhesive organic hydrogel film. The flexible electrode layer consists of a flexible substrate and interdigitated electrodes. The flexible photoexcitation layer includes a flexible circuit substrate, a flexible photoexcitation circuit, and a low-power micro-LED array, arranged according to the interdigitated electrode structure and spatial electric field distribution, forming a spatial gradient light field distribution within the flexible gas-sensitive material layer. This sensor effectively overcomes the shortcomings of existing flexible gas sensors in terms of room-temperature response performance and long-term stability. It exhibits excellent flexibility and mechanical deformation adaptability, multiple operating modes, and achieves highly sensitive detection and selective identification of target gases at room temperature.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a photoexcited flexible room temperature gas sensor, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds and other toxic and hazardous substances are widely present in industrial emissions, indoor decoration, and vehicle exhaust, making their detection crucial for environmental protection, health monitoring, and industrial safety. [1] Current mainstream gas sensors are mainly based on semiconductor metal oxides. [2] Infrared absorption [3] and surface acoustic wave principle [4] However, due to limitations in material properties and device structure, the aforementioned gas sensors still have the following drawbacks: Semiconductor metal oxide sensors rely on changes in surface resistance caused by gas adsorption, often requiring high temperatures of 200℃-400℃ to activate the gas-sensitive reaction, resulting in high power consumption, difficulty in integration, and poor safety in flammable and explosive environments; Infrared sensors achieve qualitative and quantitative analysis by detecting the characteristic infrared absorption peaks of gas molecules, relying on precision optical components, resulting in high cost, large size, and difficulty in miniaturization, limiting their application in portable scenarios; Surface acoustic wave sensors utilize the mass load or sound wave frequency shift caused by gas adsorption for detection, offering advantages such as high sensitivity and fast response speed, but due to the rigidity of the piezoelectric substrate material, they cannot be adapted to curved surface bonding and wearable scenarios.

[0003] In recent years, flexible gas sensors [5] This has become a research hotspot, with devices based on hydrogels and organic hydrogels attracting particular attention. These devices combine flexibility and low power consumption, making them perfectly suited for complex curved surface applications such as wearables. Organic hydrogels, in particular, utilize non-volatile organic solvents to construct multi-network structures, effectively suppressing moisture evaporation and freezing, significantly improving the intrinsic stability of devices under long-term cyclic service and complex deformation, making them an ideal platform for constructing highly stable flexible room-temperature gas sensors. However, existing flexible gas sensors primarily focus on the detection and sensing of physical stimuli such as pressure, strain, humidity, and temperature. [6-8] Research and development of flexible sensors for gas detection has been slow, especially for room-temperature photoexcited flexible sensors, which face multiple technical bottlenecks:

[0004] First, most flexible gas-sensitive materials have insufficient room temperature activity, resulting in weak response and poor selectivity.

[0005] Second, existing photo-excited flexible sensors only use static excitation with a fixed light intensity, which cannot regulate the adsorption-desorption behavior of gas at the gas-sensitive interface and cannot achieve accurate identification of multi-component / homogeneous gases.

[0006] Third, the photoexcitation unit, electrode layer and gas-sensitive layer are not integrated into one unit. Misalignment of light leads to low utilization rate, severe performance degradation after bending, and poor flexibility and stability.

[0007] Fourth, most light excitation systems are high-power light sources with high power consumption, which does not meet the requirements for portability / wearability, and they lack dynamic light intensity modulation mechanisms, making it impossible to expand the dimensions of response characteristics.

[0008] In summary, existing sensors cannot simultaneously meet the comprehensive requirements of flexible wearability, low power consumption at room temperature, high sensitivity, high selectivity, and inherent safety in flammable and explosive environments. There is an urgent need to develop an integrated, dynamically adjustable, portable flexible room temperature gas sensor to achieve accurate, real-time, and safe on-site detection of toxic and harmful gases in wearable devices, portable sensing devices, and electronic noses.

[0009] The cited references are as follows:

[0010] [1] Zhang T, Li G, Yu Y, et al. Atmospheric diffusion profiles and health risks of typical VOC: Numerical modeling study[J]. Journal of CleanerProduction, 2020, 275: 122982.

[0011] [2] Das S, Jayaraman V. SnO2: A comprehensive review on structures and gas sensors[J]. Progress in Materials Science, 2014, 66: 112-255.

[0012] [3] Jha R K. Non-dispersive infrared gas sensing technology: A review[J]. IEEE Sensors Journal, 2021, 22(1): 6-15.

[0013] [4] Barochi G, Rossignol J, Bouvet M. Development of microwave gassensors[J]. Sensors and Actuators B: Chemical, 2011, 157(2): 374-379.

[0014] [5] Luo Y, Li J, Ding Q, et al. Functionalized hydrogel-based wearable gas and humidity sensors[J]. Nano-Micro Letters, 2023, 15(1): 136.

[0015] [6] Han S, Liu C, Lin X, et al. Dual conductive network hydrogel for a highly conductive, self-healing, anti-freezing, and non-drying strain sensor[J]. ACS Applied Polymer Materials, 2020, 2(2): 996-1005.

[0016] [7] Lu X, Mo Z, Liu Z, et al. Robust, efficient, and recoverable thermocells with zwitterion-boosted hydrogel electrolytes for energy-autonomous and wearable sensing[J]. Angewandte Chemie International Edition, 2024, 63(29): e202405357.

[0017] [8] Liang Y, Ding Q, Wang H, et al. Humidity sensing of stretchable and transparent hydrogel films for wireless respiration monitoring[J]. Nano-Micro Letters, 2022, 14(1): 183. Summary of the Invention

[0018] To address the problems existing in the prior art, the present invention aims to provide a photoexcited flexible room temperature gas sensor and its fabrication method. By fabricating a flexible sensitive material layer, a flexible electrode layer, and a flexible photoexcitation layer, a flexible sensor with a spatial gradient photoexcitation structure is constructed. This sensor exhibits excellent toughness and mechanical deformation adaptability, solving the problems of insufficient flexibility and excessively high operating temperature of traditional rigid gas sensors. Furthermore, the fabricated flexible room temperature gas sensor is suitable for different operating modes, can detect multiple gases, and can operate safely and reliably at room temperature. It possesses advantages of flexibility, low energy consumption, and intrinsic safety. Simultaneously, it can be used to fabricate wearable devices, portable sensing devices, and electronic noses, meeting the requirements of portability, intrinsic safety, and real-time gas monitoring.

[0019] The objective of this invention is achieved through the following technical solution:

[0020] In a first aspect, the present invention provides a photoexcited flexible room temperature gas sensor, comprising a flexible gas-sensitive material layer, a flexible electrode layer, and a flexible photoexcitation layer, wherein the flexible electrode layer serves as an intermediate layer, forming a flexible photo-electric coupling sandwich structure; wherein the flexible gas-sensitive material layer is a self-adhesive organic hydrogel film; the flexible electrode layer comprises a flexible substrate and interdigitated electrodes, the interdigitated electrodes comprising an anode and a cathode; the flexible photoexcitation layer includes a flexible circuit substrate, a flexible photoexcitation circuit, and a low-power micro-LED array, the low-power micro-LED array being arranged according to the interdigitated electrode structure and spatial electric field distribution, the spacing between adjacent LEDs gradually changing along a preset direction, forming a spatial gradient light field distribution within the flexible gas-sensitive material layer.

[0021] Furthermore, the self-adhesive organic hydrogel film of the flexible gas-sensitive material layer is a polyacrylamide (PAM) / calcium alginate (CA) dual-network organic hydrogel.

[0022] Furthermore, the flexible substrate in the flexible electrode layer and the flexible circuit substrate in the flexible photoexcitation layer are selected from one or more composite films of PET, PI, PDMS, TPU and Ecoflex insulating elastomer films; the thickness of the flexible substrate in the flexible electrode layer and the flexible circuit substrate in the flexible photoexcitation layer are both 50μm-500μm.

[0023] Furthermore, the material of the interdigitated electrodes in the flexible electrode layer is selected from one or more composite materials selected from metallic materials, carbon materials, conductive adhesives, graphene and graphene derivatives.

[0024] Furthermore, a flexible photoexcitation circuit is fabricated on the surface of a flexible circuit substrate, and a low-power micro LED array is integrated to form a flexible photoexcitation layer. The material of the flexible photoexcitation circuit is selected from one or more composite materials of metal materials, carbon materials, conductive adhesives, graphene and graphene derivatives.

[0025] The low-power micro-LED array adopts a non-uniform spatial gradient arrangement. The low-power micro-LEDs are connected in series, parallel, or a combination of series and parallel. Each low-power micro-LED is connected in series with a protective resistor. The low-power micro-LED array is soldered to the wires of the flexible photoexcitation circuit by high-temperature resistant conductive adhesive.

[0026] Furthermore, the gradient ratio of the non-uniform spatial gradient arrangement of the low-power micro LED array is (4-6):(2-4):(2-3):1;

[0027] The area power of a single low-power microLED in the low-power microLED array is 1 μW / cm². 2 -100μW / cm 2 The emission wavelength range is 254nm-980nm.

[0028] Secondly, the present invention provides a method for fabricating a photoexcited flexible room temperature gas sensor, comprising the following steps:

[0029] Preparation of flexible gas-sensitive material layer: self-adhesive organic hydrogel was prepared by sol-gel process;

[0030] Fabrication of flexible electrode layer: The interdigitated electrode is fabricated on a flexible substrate by one or more of the following processes: inkjet printing, direct writing printing, sputtering, etching, in-situ growth, and transfer printing.

[0031] Fabrication of a flexible photoexcitation layer: A flexible photoexcitation circuit is fabricated on the surface of a flexible circuit substrate using screen printing, inkjet printing, photolithography, and etching processes. Then, according to the interdigitated structure and spatial electric field distribution of the flexible electrode layer, a non-uniform spatial gradient arrangement of low-power micro-LEDs and their series protection resistors is completed by bonding them with high-temperature resistant conductive adhesive and then curing them with ultraviolet light. The low-power micro-LEDs are connected in series, parallel, or series-parallel, requiring only one power supply interface to form a low-power micro-LED array with spatial gradient.

[0032] Integrated fabrication of flexible gas sensors: Utilizing the self-adhesive properties of the organic hydrogel in the flexible gas-sensitive material layer, it is directly attached to the surface of the interdigitated electrodes of the flexible electrode layer. A liquid adhesive sealing process is used to bond the low-power micro-LED array of the flexible photoexcitation layer to the interdigitated electrode interface of the flexible electrode layer in a stacked configuration. Then, ultrafine wires are soldered to the pre-set contact pads of the interdigitated electrodes and the flexible photoexcitation circuit to complete the electrical connection.

[0033] Furthermore, the method for fabricating the photoexcited flexible room temperature gas sensor includes the following steps:

[0034] Preparation of flexible gas-sensitive material layer: A PAM / CA dual-network organic hydrogel with a size of 10mm×10mm×1mm was prepared by sol-gel process;

[0035] Fabrication of flexible electrode layer: Through etching process, laser patterning operation is performed on the surface of flexible substrate with a thickness of 200μm to etch circuit pattern and micro-via, and then metallization operation is performed to chemically plate copper to form a conformal copper layer with a thickness of 8μm-12μm and a minimum feature size of 0.1mm. Then, protective film is laminated, gold is electroplated for surface treatment and circuit marking is screen printed.

[0036] Fabrication of a flexible photoexcitation layer: Through etching, a laser patterning operation is performed on the surface of a 200μm thick flexible circuit substrate to etch circuit patterns and micro-vias. Then, a conformal copper layer is formed by chemical copper plating. After that, a protective film is laminated, gold is electroplated for surface treatment, and circuit markings are screen printed. According to the interdigitated structure and spatial electric field distribution of the flexible electrode layer, low-power micro-LEDs and their series protective resistors are welded using high-temperature resistant conductive adhesive to complete a non-uniform spatial gradient arrangement. After UV curing for 1 hour, permanent fixation is achieved. The low-power micro-LEDs are connected in series, parallel, or series-parallel. Only one power supply interface is needed to form a low-power micro-LED array with spatial gradient. The size of the micro-LED array is 1.6mm × 0.8mm.

[0037] Integrated fabrication of flexible gas sensors: Utilizing the self-adhesive properties of PAM / CA dual-network organic hydrogel, it is directly attached to the surface of the interdigitated electrodes of the flexible electrode layer. A liquid adhesive sealing process is used to bond the low-power micro-LED array of the flexible photoexcitation layer to the interdigitated electrode interface of the flexible electrode layer with adhesive in a stacked configuration. Then, ultrafine wires are soldered to the pre-set contact pads of the interdigitated electrodes and the flexible photoexcitation circuit to complete the electrical connection.

[0038] Thirdly, the present invention provides an application of a photoexcited flexible room temperature gas sensor in wearable gas detection devices or portable gas detection devices.

[0039] Furthermore, the photo-excited flexible room-temperature gas sensor is used in multiple operating modes, namely, the low-power micro-LED array operates in static light intensity mode or dynamic light intensity modulation mode. The dynamic light intensity modulation mode is one of the following waveforms, or a combination of the above: rectangular wave modulation, triangular wave modulation, trapezoidal wave modulation, and sine wave modulation. The output signal of the photo-excited flexible room-temperature gas sensor is a current, which comes from the flexible electrode layer. The operating voltage of the flexible electrode layer is 1V-10V, and the operating voltage range of the flexible photo-excitation circuit is 1V-10V. The power supply voltage of the low-power micro-LED is a constant value in static light intensity mode, and a time-varying value in dynamic light intensity modulation mode.

[0040] When the operating mode is dynamic light intensity modulation mode, it selects one or more waveforms from rectangular wave modulation, triangular wave modulation, trapezoidal wave modulation, and sine wave modulation, and optimizes the modulation waveform parameters including: light intensity range, modulation period, duty cycle, and symmetry, wherein the light intensity range is 1μW / cm². 2 -100μW / cm 2 The modulation period is >10s, and the duty cycle and symmetry D are 0% < D < 100%. The low-power micro-LED array is driven by dynamic time-varying voltage to construct an adjustable spatiotemporal light field inside the flexible gas-sensitive material layer, realizing the dynamic control of the microenvironment of organic hydrogel and the gas adsorption-desorption dynamics. The spatial gradient light field and dynamic light intensity modulation work together to construct a spatiotemporally changing photoresponsive microenvironment inside the flexible gas-sensitive material layer, regulate the adsorption-desorption behavior of gas molecules at the sensitive interface, and thus enhance the selective recognition ability of different gas molecules.

[0041] Advantages and effects of the present invention:

[0042] 1. Compared with traditional rigid gas sensors, the present invention adopts a sandwich integrated structure composed of a flexible photoexcitation layer, a flexible electrode layer and a flexible gas-sensitive material layer, which has excellent flexibility and mechanical deformation adaptability, and can be applied to flexible application scenarios such as wearable devices, electronic skin, portable detection devices and electronic noses.

[0043] 2. Compared to traditional semiconductor gas sensors that rely on heaters to maintain high operating temperatures and traditional flexible gas sensors that do not employ photoexcitation structures, this invention utilizes a non-uniform spatial gradient LED arrangement to create a spatial gradient light field distribution within the flexible gas-sensitive material layer. This, in turn, modulates the activity of polar functional groups within the organic hydrogel, the hydrogen bond network state of water molecules, and the adsorption-desorption kinetics of gas molecules, thereby improving the sensor's gas-sensing response performance. This enables gas detection at room temperature, effectively reducing device power consumption and system hardware costs, improving detection safety in flammable and explosive environments, and significantly enhancing the response sensitivity to target gases while achieving selective identification.

[0044] 3. Compared with large-scale laboratory analytical equipment such as gas chromatographs, this invention has the advantages of high structural integration, miniaturization, low power consumption, and strong portability. At the same time, it improves the room temperature detection sensitivity and response stability through dynamic light field modulation, making it more suitable for integration into embedded systems and portable intelligent detection terminals. In dynamic light excitation mode, by adjusting the light intensity, frequency, and duty cycle of the LED array, the state of water molecules, the activity of polar functional groups, and the gas adsorption-desorption kinetics in the PAM / CA dual-network organic hydrogel are dynamically controlled, achieving highly sensitive detection and selective identification of target gases under room temperature conditions.

[0045] 4. This invention improves the response stability, repeatability, and mechanical flexibility of the sensor under room temperature conditions through the synergistic effect of light field modulation and flexible three-layer structure, and enhances the sensitivity and selectivity of target gas detection, thereby effectively overcoming the problems of insufficient response performance and long-term stability of existing flexible gas sensors. Attached Figure Description

[0046] Figure 1 This is an exploded view of the structure of the photoexcited flexible room temperature gas sensor in Example 1;

[0047] Figure 2 This is a schematic diagram of the interdigitated electrode structure in the flexible electrode layer of Example 1;

[0048] Figure 3 This is a schematic diagram of the non-uniform spatial gradient arrangement of the low-power micro-LED array in the flexible photoexcitation layer of Example 1;

[0049] Figure 4 This is a schematic diagram of the preparation process of the flexible gas-sensitive material layer in Example 1;

[0050] Figure 5 The image shows a scanning electron microscope (SEM) image of the PAM / CA dual-network organic hydrogel prepared in Example 1 after lyophilization.

[0051] Figure 6 The image shows the tensile-strain curve of the PAM / CA dual-network organic hydrogel prepared in Example 1.

[0052] Figure 7 The graph shows the differential scanning calorimetry test curve of the PAM / CA dual-network organic hydrogel prepared in Example 1.

[0053] Figure 8 The graph shows the weight change of the PAM / CA dual-network organic hydrogel prepared in Example 1 after 50 hours of water loss.

[0054] Figure 9 The UV-Vis absorption spectrum of the PAM / CA dual-network organic hydrogel prepared in Example 1 is shown below.

[0055] Figure 10 This is a schematic diagram of the gas-sensitive testing platform construction for the photoexcited flexible room temperature gas sensor in Examples 1 and 2.

[0056] Figure 11 The image shows the dynamic response curves of the photoexcited flexible room temperature gas sensor in Example 1 to different concentrations of formic acid in static light intensity operating mode.

[0057] Figure 12 The calibration response diagram of the photoexcited flexible room temperature gas sensor in Example 1 to formic acid gas of different concentrations is shown.

[0058] Figure 13 This is a calibration response diagram of the photoexcited flexible room temperature gas sensor in Example 1 to 10 ppm of various pollutant gases;

[0059] Figure 14 The image shows the dynamic response curves of the photoexcited flexible room temperature gas sensor in Example 1 to different concentrations of formic acid without ultraviolet light excitation.

[0060] Figure 15 This is a graph showing the response of the photoexcited flexible room temperature gas sensor in Example 1 to 10 ppm formic acid over a period of 30 days.

[0061] Figure 16 The graph shows the response of the photoexcited flexible room temperature gas sensor in Example 1 to 10 ppm formic acid at different bending angles.

[0062] Figure 17 This is a graph showing the changes in ultraviolet excitation voltage and light intensity of a low-power micro-LED array in dynamic ultraviolet light intensity modulation for the photoexcited flexible room temperature gas sensor in Example 2.

[0063] Figure 18 Example 2: Single-cycle response fingerprints of a photoexcited flexible room-temperature gas sensor to different concentrations of organic acid gases under dynamic ultraviolet light intensity modulation; where (a) is the control group air, (b) formic acid, (c) acetic acid, and (d) propionic acid.

[0064] Figure 19 Example 2: Single-cycle noise fingerprints of a photoexcited flexible room-temperature gas sensor for different concentrations of formic acid, acetic acid, and propionic acid under dynamic ultraviolet light intensity modulation; where (a) is the control group air, (b) formic acid, (c) acetic acid, and (d) propionic acid.

[0065] Explanation of reference numerals in the attached figures:

[0066] 1. Flexible photoexcitation layer; 2. Flexible electrode layer; 3. Flexible gas-sensitive material layer; 4. Sealant Ecoflex colloid; 5. Flexible circuit substrate; 6. Flexible photoexcitation circuit; 7. Low-power micro LED array; 8. Flexible substrate; 9. Interdigitated electrode; 10. Protective resistor; 11. Low-power micro LED. Detailed Implementation

[0067] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0068] A photoexcited flexible room temperature gas sensor is composed of a flexible gas-sensitive material layer, a flexible electrode layer, and a flexible photoexcitation layer, with the flexible electrode layer serving as the intermediate layer, forming a flexible photo-electric coupling sandwich structure. The flexible gas-sensitive material layer is a self-adhesive PAM / CA dual-network organic hydrogel. The flexible electrode layer consists of a flexible substrate (200 μm thick) and interdigitated electrodes, which are composed of an anode and a cathode, and the material of the interdigitated electrodes is copper. The flexible photoexcitation layer comprises a flexible circuit substrate (200 μm thick), a flexible photoexcitation circuit, and a low-power micro-LED array. The flexible photoexcitation circuit is fabricated on the surface of the flexible circuit substrate, and the low-power micro-LED array is integrated to form the flexible photoexcitation layer. The conductive material of the flexible photoexcitation circuit is copper. The low-power micro-LED array adopts a non-uniform spatial gradient arrangement with a gradient ratio of (4-6):(2-4):(2-3):1. The low-power micro-LEDs are connected in series, parallel, or a combination of series and parallel. Each low-power micro-LED is connected in series with a protective resistor. The low-power micro-LED array is soldered to the wires of the flexible photoexcitation circuit using high-temperature resistant conductive adhesive. The optical power of a single low-power micro-LED is 1 μW / cm². 2 -100μW / cm 2 The emission wavelength range is 365nm-370nm, the size is 1.6mm×0.8mm, the wavelength is 365nm ultraviolet light, the working voltage is 3.0V-3.4V, and the working current is <20mA.

[0069] A method for fabricating a photoexcited flexible room temperature gas sensor includes the following steps:

[0070] Fabrication of flexible electrode layer:

[0071] Circuit patterns and micro-vias were etched on the surface of a 200μm thick transparent PET film substrate using a 20W CO2 laser system. Then, a conformal copper layer with a thickness of 8μm-12μm and a minimum feature size of 0.1mm was formed by chemical copper plating. Finally, a protective film was laminated, gold was electroplated, and circuit markings were screen printed.

[0072] Preparation of flexible gas-sensitive material layer:

[0073] A PAM / CA dual-network organic hydrogel with dimensions of 10 mm × 10 mm × 1 mm was prepared by a sol-gel process, as detailed below:

[0074] (1) Preparation of precursor solution: First, 9g of acrylamide (AM), 1.2g of sodium alginate (SA), 6mg of N,N'-methylenebisacrylamide (MBA) and 60mg of ammonium persulfate (APS) were added to 60mL of deionized water in sequence; then, the mixture was stirred continuously at 800 r / min for 1h at room temperature to fully dissolve the components and form a uniform and transparent precursor solution. In order to promote the subsequent free radical polymerization reaction, 20μL of N,N,N',N'-tetramethylethylenediamine (TEMED) was added to the above mixed solution as a polymerization promoter, and the mixture was stirred until the system was uniform.

[0075] (2) Construction of PAM network: The prepared precursor solution was slowly poured into a pre-prepared mold and heated at 70°C for 1 hour. During the heating process, APS decomposed to generate free radicals, which initiated the polymerization reaction of AM monomers. At the same time, MBA participated in the network construction as a chemical crosslinking agent, thereby forming a polyacrylamide (PAM) network with a three-dimensional crosslinked structure. After the reaction was completed, PAM semi-finished hydrogel was obtained.

[0076] (3) LiBr ion-conducting treatment: The obtained PAM semi-finished hydrogel was cut into regular sizes of 10mm×10mm×1mm, and then immersed in a 50wt% LiBr solution for 25min at 25℃, so that Li + Ions diffuse fully into the hydrogel, a process that effectively enhances the ion migration capacity within the hydrogel, thereby improving the material's ionic conductivity and environmental stability.

[0077] (4) Construction of the calcium alginate ion network: After LiBr treatment, the hydrogel was further immersed in 1M CaCl2 solution at 25℃ for 20 min. During this process, Ca... 2+ It undergoes ionic cross-linking with the carboxyl groups on the sodium alginate molecular chain to form a typical "Egg-box" calcium alginate (CA) network; under the synergistic effect of the PAM covalent network and the CA ionic network, a PAM / CA dual-network hydrogel was successfully constructed.

[0078] (5) Preparation of PAM / CA dual-network organic hydrogel: To further improve the antifreeze and moisturizing stability of the hydrogel, the prepared PAM / CA dual-network hydrogel was placed in pure glycerol (Glycerol, Gly) and soaked at 25°C for 1 hour. During the soaking process, glycerol gradually replaced some water and entered the interior of the hydrogel network, thus forming a water / glycerol mixed solvent system. After glycerol solvent replacement, PAM / CA dual-network organic hydrogel was finally obtained. This organic hydrogel not only has excellent flexibility and mechanical stability, but also has good antifreeze performance, moisturizing performance and ionic conductivity. This process realizes a dual-network hydrogel with high flexibility, high mechanical strength and high stability by constructing a PAM covalent network and a CA ionic network synergistic reinforcement structure. At the same time, by regulating with LiBr ions and replacing with glycerol solvent, the material is endowed with excellent ionic conductivity, antifreeze and long-term moisturizing performance, providing a stable flexible functional substrate for flexible electronic devices and wearable sensing systems.

[0079] Fabrication of a flexible photoexcitation layer:

[0080] Circuit patterns and microvias were etched onto a 200μm thick transparent PET film substrate using a 20W CO2 laser system. A conformal copper layer with a thickness of 8μm-12μm and a minimum feature size of 0.1mm was then formed via chemical copper plating. Following this, a protective film was laminated, gold plating was applied, and circuit markings were screen-printed. Based on the interdigitated structure and spatial electric field distribution of the flexible electrode layer, low-power micro-LEDs and their series protective resistors were bonded using high-temperature conductive adhesive to achieve a non-uniform spatial gradient arrangement. UV curing for 1 hour ensured permanent fixation. The low-power micro-LEDs could be connected in series, parallel, or a combination of series and parallel, requiring only a single power supply interface to form a low-power micro-LED array with a spatial gradient. The micro-LED array measures 1.6mm × 0.8mm. Non-uniform spatial gradient LEDs are arranged within the flexible gas-sensitive material layer to form a spatial gradient light field distribution. High-density LED regions correspond to the interdigital gaps in the flexible electrode layer, enhancing the local light field intensity and improving the interaction efficiency between gas molecules and the gas-sensitive material. Low-density LED regions correspond to non-sensitive regions, forming a spatial gradient light field distribution within the flexible gas-sensitive material layer. By modulating the activity of polar functional groups, the hydrogen bond network state of water molecules, and the adsorption-desorption behavior of gas molecules in the PAM / CA dual-network organic hydrogel, enhanced response and selective recognition of target gases at room temperature are achieved, significantly improving the sensor's sensitivity, response speed, and recovery performance.

[0081] Integrated fabrication of flexible gas sensors:

[0082] Utilizing the self-adhesive properties of the PAM / CA dual-network organic hydrogel, it is directly attached to the surface of the interdigitated electrodes of the flexible electrode layer. A liquid adhesive sealing process is used to precisely seal the edges. The low-power micro-LED array of the flexible photoexcitation layer and the interdigitated electrode interface of the flexible electrode layer are assembled in a stacked configuration using Ecoflex adhesive, ensuring that the flexible photoexcitation layer and the flexible electrode layer maintain coordinated deformation compatibility. Then, ultrafine wires (0.3 mm in diameter, rated current 0.62 A) are soldered to the pre-set contact pads of the interdigitated electrodes and the flexible photoexcitation circuit to complete the electrical connection.

[0083] An application of a photoexcited flexible room temperature gas sensor in wearable or portable gas detection devices is disclosed. This sensor is suitable for multiple operating modes, including a low-power micro-LED array operating in either a static light intensity mode or a dynamic light intensity modulation mode. The dynamic light intensity modulation mode utilizes one or a combination of rectangular wave modulation, triangular wave modulation, trapezoidal wave modulation, and sine wave modulation, with rectangular wave modulation being preferred. The output signal of the photoexcited flexible room temperature gas sensor is a current originating from a flexible electrode layer. The operating voltage of the flexible electrode layer is 1V-10V, and the operating voltage range of the flexible photoexcitation circuit is also 1V-10V. The power supply voltage of the low-power micro-LED is constant in the static light intensity mode and time-varying in the dynamic light intensity modulation mode.

[0084] When the operating mode is dynamic light intensity modulation mode, a combination mode of one or more waveforms selected from rectangular wave modulation, triangular wave modulation, trapezoidal wave modulation, and sine wave modulation is preferred. The parameters for optimizing the modulation waveform include: light intensity range, modulation period, duty cycle, and symmetry, wherein the light intensity range is 1 μW / cm². 2 -100μW / cm 2 The modulation period is >10s, and the duty cycle and symmetry D are 0% < D < 100%. The preferred parameters for rectangular wave modulation are as follows: light intensity range is 12μW / cm². 2 -76μW / cm 2 The modulation period is 100s, and the duty cycle and symmetry are both 50%. The low-power micro-LED array is driven by dynamic time-varying voltage to construct an adjustable spatiotemporal light field inside the flexible gas-sensitive material layer, realizing the dynamic control of the microenvironment of organic hydrogel and the gas adsorption-desorption dynamics. The spatial gradient light field and dynamic light intensity modulation work together to construct a spatiotemporally changing photoresponsive microenvironment inside the flexible gas-sensitive material layer, regulate the adsorption-desorption behavior of gas molecules at the sensitive interface, and thus enhance the selective recognition ability of different gas molecules.

[0085] The gas detection mechanism of gas-sensitive materials is mainly based on the interaction between the material and target gas molecules. Through physical or chemical changes (such as conductivity, resistance, optical properties, and mass), the gas components are converted into measurable signals. Organic hydrogel materials achieve gas detection by adsorbing gases through electrostatic interactions, hydrogen bonds, and coordination bonds, followed by redox reactions on the electrodes. Since the adsorption capacity of these materials for gas molecules is limited at room temperature, the response of gas-sensitive materials is restricted. Photoexcitation can significantly improve the gas-sensing performance of these materials at room temperature. Furthermore, photoexcitation induces structural relaxation or dynamic adjustment of the doping state of polymer segments, exposing more active sites or increasing the specific surface area, thereby improving the adsorption and diffusion efficiency of the target gas. For hydrogels and organic hydrogels, photoexcitation generates abundant polar groups on the material surface, promoting the adsorption of polar gases through hydrogen bonds, electrostatic interactions, and coordination bonds. Photoexcitation can also trigger a volume phase transition in (organic) hydrogels, expanding the pore structure and accelerating the adsorption and diffusion rate of gas molecules on the (organic) hydrogel surface. This invention uses flexible gas-sensitive materials and flexible devices as the main components of a gas sensor, giving the gas sensor flexibility and significantly improving the gas-sensing performance of the sensor at room temperature through photoexcitation.

[0086] Example 1

[0087] A photoexcited flexible room temperature gas sensor, such as Figure 1 As shown, the structure comprises a flexible photoexcitation layer 1, a flexible electrode layer 2, and a flexible gas-sensitive material layer 3, with the flexible electrode layer 2 serving as the intermediate layer, forming a flexible photo-electric coupling sandwich structure. The flexible photoexcitation layer includes a flexible circuit substrate 5 (transparent PET insulating elastomer film), a flexible photoexcitation circuit 6, and a low-power micro-LED array 7. The flexible photoexcitation circuit is fabricated on the surface of the transparent PET insulating elastomer film, and the low-power micro-LED array is integrated to form the flexible photoexcitation layer 1. The conductive wires of the flexible photoexcitation circuit 6 are made of copper. The low-power micro-LED array is arranged in a non-uniform spatial gradient with a size of 1cm × 1cm, such as... Figure 3 As shown, the array consists of 10 identical low-power micro UV LEDs connected in series and parallel. Each low-power micro LED 11 is connected in series with a 100Ω protective resistor 10. The LED array is arranged in a non-uniform spatial gradient manner based on the interdigitated structure of the flexible electrode layer to form a spatial gradient light field with a gradient ratio of 4:3:2:1. The low-power micro LED array is soldered to the wires of the flexible photoexcitation circuit using high-temperature resistant conductive adhesive. The low-power micro LED 11 is a micrometer-scale light-emitting diode with a package size of 1.6mm × 0.8mm and an area power of 1μW / cm² for a single low-power micro LED 11. 2 -100μW / cm 2The emission wavelength range is 365nm-370nm, and the operating voltage is 3.0V-3.4V. The flexible electrode layer consists of a flexible substrate 8 (transparent PET insulating elastomer film) and interdigitated electrodes 9, such as... Figure 2 As shown, the interdigitated electrode 9 consists of an anode and a cathode. The material of the interdigitated electrode is copper, and its spatial topology is interdigitated. The size of the interdigitated electrode is 1cm × 1cm, and the width and gap of the interdigitated fingers are 200μm. The flexible gas-sensitive material layer is a self-adhesive PAM / CA dual-network organic hydrogel with a size of 10mm × 10mm × 1mm.

[0088] The fabrication method of the photoexcited flexible room temperature gas sensor in Example 1 includes the following steps:

[0089] Preparation of flexible gas-sensitive material layer:

[0090] PAM / CA dual-network organic hydrogels were prepared using a sol-gel process, such as... Figure 4 As shown, the specific process is as follows:

[0091] (1) Preparation of precursor solution: First, add 9g AM, 1.2g SA, 6mg MBA and 60mg APS to 60mL of deionized water in sequence; then, stir continuously for 1h at 800r / min using a magnetic stirrer at room temperature to fully dissolve each component and form a uniform and transparent precursor solution. Add 20μL TEMED as a polymerization accelerator to the above mixed solution and continue stirring until the system is uniform.

[0092] (2) Construction of PAM network: The prepared precursor solution was slowly poured into the pre-prepared mold and heated at 70℃ for 1 hour. After the reaction was completed, PAM semi-finished hydrogel was obtained.

[0093] (3) LiBr ion conduction treatment: The obtained PAM semi-finished hydrogel was cut into regular sizes of 10mm×10mm×1mm, and then immersed in 50wt% LiBr solution for 25min at 25℃.

[0094] (4) Construction of calcium alginate ion network: After LiBr treatment, the hydrogel was further placed in 1M CaCl2 solution and soaked at 25℃ for 20 min to construct PAM / CA double network hydrogel.

[0095] (5) Preparation of PAM / CA dual-network organic hydrogel: The PAM / CA dual-network hydrogel was placed in Gly and soaked at 25℃ for 1 h. After glycerol solvent replacement, a PAM / CA dual-network organic hydrogel with dimensions of 10 mm × 10 mm × 1 mm was finally obtained. The prepared PAM / CA dual-network organic hydrogel was freeze-dried and observed by SEM. Figure 5 As shown, the material exhibits a rich porous structure; the uniform and interpenetrating porous structure effectively promotes the diffusion of target molecules and ion transport. Tensile-strain tests were performed on the PAM / CA dual-network organic hydrogel, as shown... Figure 6 As shown, the gel remains intact and undamaged even when stretched to 300% strain, indicating that the prepared organic hydrogel gas-sensitive layer possesses good flexibility and stretchability. DSC testing was performed on the PAM / CA dual-network organic hydrogel, as shown... Figure 7 As shown, its freezing point is below -57.3℃, indicating that the prepared organic hydrogel has strong antifreeze properties. A 50-hour water loss experiment was conducted on the PAM / CA dual-network organic hydrogel in air (25°C, 40%RH), and the results were as follows: Figure 8 As shown, the mass loss of the organic hydrogel decreased by only 26.5% within 50 hours, indicating that the prepared organic hydrogel has excellent anti-drying properties. The ideal mechanical properties, freeze resistance, and anti-drying properties of the flexible gas-sensitive material layer ensure the long-term stability of this photoexcited flexible room-temperature gas sensor. The ultraviolet light absorption capacity of the PAM / CA dual-network organic hydrogel was tested, as shown... Figure 9 The ultraviolet-visible absorption spectrum shown indicates that its light absorption band is between 200nm and 400nm, demonstrating that it has a broad-spectrum ultraviolet light absorption capability.

[0096] Fabrication of flexible electrode layer:

[0097] Interdigitated electrodes were fabricated on a 200 μm thick transparent PET insulating elastomer film substrate using a multi-step micro-nano fabrication process. The fabrication process included two stages: laser patterning and metallization. First, an interdigitated circuit pattern and micro-vias were etched on the PET film using a 20 W CO2 laser system. Then, a conformal copper layer with a thickness of 10 μm and a minimum feature size of 0.1 mm was formed by chemical copper plating. After that, a protective film was laminated, gold was electroplated for surface treatment, and circuit markings were screen printed. The size of the interdigitated electrodes was 1 cm × 1 cm, and the width and gap of the interdigitated electrodes were 200 μm.

[0098] Fabrication of a flexible photoexcitation layer:

[0099] The flexible photoexcitation layer uses silver wires as the circuit material. An ultraviolet excitation array (low-power micro-LED array) is fabricated on a 200μm thick transparent PET insulating elastomer film substrate using a multi-step micro-nano fabrication process. The fabrication process includes three stages: laser patterning, metallization, and component integration. First, a 20W CO2 laser system is used to etch circuit patterns and microvias on the transparent PET film. Then, a conformal copper layer with a thickness of 10μm and a minimum feature size of 0.1mm is formed through chemical copper plating. Next, a protective film is laminated, gold is electroplated, and circuit markings are screen-printed. Ten series-parallel low-power micro-LEDs (requiring only one power supply interface) are bonded together using high-temperature conductive adhesive. The low-power micro-LED array is arranged in a non-uniform spatial gradient according to the interdigitated structure of the flexible electrode layer. The array is a 1cm×1cm rectangular matrix, forming a spatial gradient light field with a gradient ratio of 4:3:2:1. The parameters of the low-power micro-UV LED are as follows: size is 1.6mm×0.8mm, wavelength is 365nm-370nm, operating voltage is 3.0V-3.4V, and maximum operating current is 20mA. Then, UV curing is performed for 1 hour to achieve permanent fixation, forming a low-power micro-LED array with a spatial gradient. The size of the micro-LED array is 1.6mm×0.8mm.

[0100] Integrated fabrication of flexible gas sensors:

[0101] like Figure 1 As shown, utilizing the self-adhesive properties of the PAM / CA dual-network organic hydrogel (flexible gas-sensitive material layer 3), it is directly attached to the surface of the interdigitated electrodes 9 of the flexible electrode layer 2. A liquid adhesive is used for precise edge sealing, and Ecoflex colloid 4 is used as an interface adhesive for precise edge sealing. The low-power micro-LED array (low-power micro-LED array 7) of the flexible photoexcitation layer 1 is bonded to the interdigitated electrodes 9 of the flexible electrode layer 2 in a stacked configuration for assembly, so that the flexible photoexcitation layer 1 and the flexible electrode layer 2 maintain coordinated deformation compatibility. The ultraviolet light emitted by the flexible ultraviolet excitation layer can irradiate the surface of the organic hydrogel material through the gap between the interdigitated electrodes. Then, ultrafine wires (diameter 0.3mm, rated current 0.62A) are soldered to the interdigitated electrodes 9 and the pre-set contact pads of the flexible photoexcitation circuit 6 to complete the electrical connection.

[0102] The photoexcited flexible room-temperature gas sensor prepared in Example 1 serves as a flexible formic acid gas sensor for detecting formic acid gas at room temperature. It operates in static light intensity mode. The output signal of the photoexcited flexible room-temperature gas sensor is a current originating from the flexible electrode layer. The operating voltage of the flexible electrode layer is 1V, and the operating voltage range of the flexible photoexcitation circuit is 3.0V-3.4V. The low-power micro-LED operates at a supply voltage of 5V. A structure was constructed as follows... Figure 10 The gas-sensitive testing platform shown was used to perform gas-sensitive testing on the prepared flexible formic acid gas sensor at room temperature. Under a fixed ultraviolet excitation voltage of 5V, the intensity of the ultraviolet excitation light remained statically constant. The dynamic response curves for different formic acid concentrations are shown below. Figure 11 As shown, it can be observed that the sensor has a stable baseline current in air, while the response saturation current in formic acid gas increases with increasing formic acid concentration. To compensate for the baseline response, the sensor's response is calibrated by subtracting the baseline current value from the response saturation current value, yielding its calibrated response to different concentrations of formic acid gas, as shown below. Figure 12 As shown, the calibrated response of the sensor exhibits a good linear correlation with gas concentrations in the range of 1 ppm to 50 ppm, enabling accurate gas concentration resolution. Furthermore, the sensor's gas-sensing response to various pollutant gases at 10 ppm, including acetic acid, propionic acid, ethanol, acetone, diethyl ether, benzene, and formaldehyde, was tested. The calibrated response values ​​are shown below. Figure 13 As shown, the sensor's response to formic acid is significantly higher than its response to other gases, indicating that the photoexcited flexible room-temperature gas sensor of this invention has good selectivity for formic acid. Simultaneously, the gas response of the sensor without ultraviolet light excitation was also tested, such as... Figure 14 As shown, photoexcitation significantly improves the gas-sensing response of this flexible gas sensor. To verify the long-term stability of the sensor, a 30-day gas-sensing response change test was conducted using 10 ppm formic acid gas. Figure 15 As shown, the response change is not significant, indicating that the sensor has good long-term stability. To verify the mechanical properties and resistance to external interference of the sensor under different deformations, its response to 10 ppm formic acid gas at different bending angles was tested, as shown below. Figure 16 As shown, the sensor exhibits an approximate gas-sensitive response under different degrees of bending, indicating that it has good mechanical properties and resistance to external interference.

[0103] Example 2

[0104] The photoexcited flexible room-temperature gas sensor and its fabrication method in Example 2 are the same as in Example 1, except that the photoexcited flexible room-temperature gas sensor prepared in this example is used as an organic acid gas sensor for the selective detection of formic acid, acetic acid, and propionic acid gases in the air. A dynamic ultraviolet light intensity modulation mode is employed, aiming to expand the dimensions of the sensor's response signal and enhance the differences in response fingerprint patterns among different gas types, thereby achieving selective identification of organic acid homologues (formic acid, acetic acid, and propionic acid). Example 2 uses rectangular wave ultraviolet light intensity modulation with a period of 100s, a low-power micro-LED array input voltage range of 1V-5V, and a light intensity range of 12μW / cm². 2 -76μW / cm 2 With a duty cycle of 50%, the low-power micro-LED array exhibits high ultraviolet excitation voltage and light intensity, as shown in the figure. Figure 17 As shown.

[0105] Adopting such Figure 10 The gas-sensitive testing platform shown demonstrates the gas-sensitive testing of the organic acid gas sensor at room temperature. Under dynamic ultraviolet light intensity modulation, the intensity of the ultraviolet-excited light changes periodically. At a sampling rate of 20 Hz, the single-cycle gas-sensitive response curves for formic acid, acetic acid, propionic acid, and the control group air at different concentrations are shown below. Figure 18 As shown, subtle differences can be observed in the response fingerprint spectra of different types of gases, and the amplitude distribution of the fingerprint spectra is positively correlated with the gas concentration. Furthermore, the noise in the response mainly originates from the adsorption-desorption process of gas molecules on the hydrogel surface. Since the adsorption-desorption behavior of gas molecules is related to molecular mass, wavelet denoising is used to further separate the response noise, employing the noise fingerprint spectra of different types of gases as a subdivision feature for species identification. Figure 19 As shown, the noise fingerprint spectra of different types of gases exhibit significant differences, especially in the peak and trough regions. Therefore, the noise amplitude within the same gas type shows a consistent distribution, effectively filtering out concentration information. The response and noise fingerprint spectra obtained through dynamic ultraviolet light intensity modulation can significantly improve the fingerprint feature differences, and combined with machine learning algorithms, accurate gas type identification can be achieved.

Claims

1. A photoexcited flexible room temperature gas sensor, characterized in that, It consists of a flexible gas-sensitive material layer, a flexible electrode layer, and a flexible photoexcitation layer, with the flexible electrode layer serving as the intermediate layer, forming a flexible photo-electric coupling sandwich structure. The flexible gas-sensitive material layer is a self-adhesive organic hydrogel film. The flexible electrode layer consists of a flexible substrate and interdigitated electrodes, with the interdigitated electrodes consisting of an anode and a cathode. The flexible photoexcitation layer includes a flexible circuit substrate, a flexible photoexcitation circuit, and a low-power micro-LED array. The low-power micro-LED array is arranged according to the interdigitated electrode structure and the spatial electric field distribution, with the spacing between adjacent LEDs gradually changing along a preset direction, forming a spatial gradient light field distribution inside the flexible gas-sensitive material layer.

2. The photoexcited flexible room temperature gas sensor as described in claim 1, characterized in that, The self-adhesive organic hydrogel film of the flexible gas-sensitive material layer is a polyacrylamide (PAM) / calcium alginate (CA) dual-network organic hydrogel.

3. The photoexcited flexible room temperature gas sensor as described in claim 1, characterized in that, The flexible substrate in the flexible electrode layer and the flexible circuit substrate in the flexible photoexcitation layer are selected from one or more composite films of PET, PI, PDMS, TPU and Ecoflex insulating elastomer films; the thickness of the flexible substrate in the flexible electrode layer and the flexible circuit substrate in the flexible photoexcitation layer are both 50μm-500μm.

4. The photoexcited flexible room temperature gas sensor as described in claim 1, characterized in that, The material of the interdigitated electrodes in the flexible electrode layer is selected from one or more composite materials of metallic materials, carbon materials, conductive adhesives, graphene and graphene derivatives.

5. The photoexcited flexible room temperature gas sensor as described in claim 1, characterized in that, A flexible photoexcitation circuit is fabricated on the surface of a flexible circuit substrate, and a low-power micro LED array is integrated to form a flexible photoexcitation layer. The material of the flexible photoexcitation circuit is selected from one or more composite materials of metal materials, carbon materials, conductive adhesives, graphene and graphene derivatives. The low-power micro-LED array adopts a non-uniform spatial gradient arrangement. The low-power micro-LEDs are connected in series, parallel, or a combination of series and parallel. Each low-power micro-LED is connected in series with a protective resistor. The low-power micro-LED array is soldered to the wires of the flexible photoexcitation circuit by high-temperature resistant conductive adhesive.

6. The photoexcited flexible room temperature gas sensor as described in claim 5, characterized in that, The gradient ratio of the non-uniform spatial gradient arrangement of the low-power micro LED array is (4-6):(2-4):(2-3):1; The area power of a single low-power microLED in the low-power microLED array is 1 μW / cm². 2 -100μW / cm 2 The emission wavelength range is 254nm-980nm.

7. A method for fabricating a photoexcited flexible room temperature gas sensor as described in claim 1, characterized in that, Includes the following steps: Preparation of flexible gas-sensitive material layer: self-adhesive organic hydrogel was prepared by sol-gel process; Fabrication of flexible electrode layer: The interdigitated electrode is fabricated on a flexible substrate by one or more of the following processes: inkjet printing, direct writing printing, sputtering, etching, in-situ growth, and transfer printing. Fabrication of a flexible photoexcitation layer: A flexible photoexcitation circuit is fabricated on the surface of a flexible circuit substrate using screen printing, inkjet printing, photolithography, and etching processes. Then, according to the interdigitated structure and spatial electric field distribution of the flexible electrode layer, a non-uniform spatial gradient arrangement of low-power micro-LEDs and their series protection resistors is completed by bonding them with high-temperature resistant conductive adhesive and then curing them with ultraviolet light. The low-power micro-LEDs are connected in series, parallel, or series-parallel, requiring only one power supply interface to form a low-power micro-LED array with spatial gradient. Integrated fabrication of flexible gas sensors: Utilizing the self-adhesive properties of the organic hydrogel in the flexible gas-sensitive material layer, it is directly attached to the surface of the interdigitated electrodes of the flexible electrode layer. A liquid adhesive sealing process is used to bond the low-power micro-LED array of the flexible photoexcitation layer to the interdigitated electrode interface of the flexible electrode layer in a stacked configuration. Then, ultrafine wires are soldered to the pre-set contact pads of the interdigitated electrodes and the flexible photoexcitation circuit to complete the electrical connection.

8. The method for fabricating a photoexcited flexible room temperature gas sensor as described in claim 7, characterized in that, Includes the following steps: Preparation of flexible gas-sensitive material layer: A PAM / CA dual-network organic hydrogel with a size of 10mm×10mm×1mm was prepared by sol-gel process; Fabrication of flexible electrode layer: Through etching process, laser patterning operation is performed on the surface of flexible substrate with a thickness of 200μm to etch circuit pattern and micro-via, and then metallization operation is performed to chemically plate copper to form a conformal copper layer with a thickness of 8μm-12μm and a minimum feature size of 0.1mm. Then, protective film is laminated, gold is electroplated for surface treatment and circuit marking is screen printed. Fabrication of a flexible photoexcitation layer: A laser patterning process is used to etch circuit patterns and microvias onto a 200μm thick flexible circuit substrate. Then, a conformal copper layer is formed by chemical copper plating. A protective film is then laminated, followed by gold plating and screen printing of circuit markings. Based on the interdigitated structure and spatial electric field distribution of the flexible electrode layer, low-power micro-LEDs and their series protective resistors are welded using high-temperature conductive adhesive to achieve a non-uniform spatial gradient arrangement, followed by UV curing for 1 hour. The low-power micro-LEDs are connected in series, parallel, or a series-parallel combination, requiring only one power supply interface to form a low-power micro-LED array with a spatial gradient. The micro-LED array size is 1.6mm × 0.8mm. Integrated fabrication of flexible gas sensors: Utilizing the self-adhesive properties of PAM / CA organic hydrogel, it is directly attached to the surface of the interdigitated electrodes of the flexible electrode layer. A liquid adhesive sealing process is used to bond the low-power micro-LED array of the flexible photoexcitation layer to the interdigitated electrode interface of the flexible electrode layer with adhesive in a stacked configuration. Then, ultrafine wires are soldered to the pre-set contact pads of the interdigitated electrodes and the flexible photoexcitation circuit to complete the electrical connection.

9. The application of the photoexcited flexible room temperature gas sensor according to claim 1 in a wearable gas detection device or a portable gas detection device.

10. The application of the photoexcited flexible room temperature gas sensor as described in claim 9 in wearable gas detection devices or portable gas detection devices, characterized in that, The photoexcited flexible room temperature gas sensor is used in multiple operating modes, namely, the low-power micro-LED array operates in either a static light intensity mode or a dynamic light intensity modulation mode. The dynamic light intensity modulation mode is one of the following waveforms: rectangular wave modulation, triangular wave modulation, trapezoidal wave modulation, or sine wave modulation, or a combination of these waveforms. The output signal of the photoexcited flexible room temperature gas sensor is a current sourced from the flexible electrode layer, with an operating voltage of 1V-10V. The operating voltage range of the flexible photoexcitation circuit is also 1V-10V. The power supply voltage of the low-power micro-LED is constant in the static light intensity mode and time-varying in the dynamic light intensity modulation mode. When the operating mode is dynamic light intensity modulation mode, it selects one or more waveforms from rectangular wave modulation, triangular wave modulation, trapezoidal wave modulation, and sine wave modulation, and optimizes the modulation waveform parameters including: light intensity range, modulation period, duty cycle, and symmetry, wherein the light intensity range is 1μW / cm². 2 -100μW / cm 2 The modulation period is >10s, and the duty cycle and symmetry D are 0% < D < 100%. The low-power micro-LED array is driven by dynamic time-varying voltage to construct an adjustable spatiotemporal light field inside the flexible gas-sensitive material layer, realizing the dynamic control of the microenvironment of organic hydrogel and the gas adsorption-desorption dynamics. The spatial gradient light field and dynamic light intensity modulation work together to construct a spatiotemporally changing photoresponsive microenvironment inside the flexible gas-sensitive material layer, regulate the adsorption-desorption behavior of gas molecules at the sensitive interface, and thus enhance the selective recognition ability of different gas molecules.

Images