Gas-sensitive sensing device based on three-dimensional bionic spiral stepped structure

Abstract

The invention relates to a gas-sensitive sensor technology, and particularly discloses a gas-sensitive sensing device based on a three-dimensional bionic spiral step structure, which comprises a three-dimensional bionic spiral step substrate, a flexible electrode mounted on the inner wall of the three-dimensional bionic spiral step substrate, and a gas-sensitive film deposited on the surface of the flexible electrode. According to the device, trace gas such as volatile organic compounds and the like entering the gas chamber can be guided by the specific three-dimensional bionic spiral stepped structure to bypass along a spiral path for multiple circles and repeatedly sweep over the surface of a gas sensitive film, so that the effective contact opportunity of gas molecules and a sensitive layer is remarkably increased. By simplifying the installation mode of the three-dimensional bionic spiral stepped substrate and the flexible electrode, the background interference of small organic molecules slowly released in the curing and aging process of a traditional adhesive on trace gas detection is avoided. Meanwhile, the idea of parallel connection of multiple sensors is provided, and the problems that an existing gas sensitive sensor of a plane structure is insufficient in low-concentration gas detection sensitivity and high in detection limit are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to gas sensing technology, in particular to a gas sensitive sensing device based on three-dimensional biomimetic spiral ladder structure, which is suitable for room temperature resistance detection of trace gases such as volatile organic compounds (VOCs). BACKGROUND

[0002] In many scenarios such as industrial production, environmental monitoring and medical diagnosis, the concentration changes of various VOCs and other trace gases are often closely related to equipment leakage, air quality deterioration and even human metabolic abnormalities. In the early warning stage of these scenarios, the concentration of related gases is usually at the sub-ppm (the concentration of gas is expressed in units of volume fraction per million, hereinafter referred to as ppm) or even ppb (volume fraction per billion, hereinafter referred to as ppb) level. If the minimum detection limit (Limit of Detection, LoD) of the sensor is high, it is difficult to achieve early high-sensitivity alarm and monitoring.

[0003] Most of the widely used resistance-type gas sensors adopt a cylindrical or flat plate structure. Taking the flat plate structure as an example, electrodes are usually prepared on a flat ceramic sheet, glass sheet or silicon sheet, then a layer of gas sensitive material is dropped or spin-coated on the surface of the electrode, and finally the flat plate chip is directly placed in a nearly straight gas chamber. When the target gas enters from one side of the gas chamber, it passes above the sensor along a basically straight or slightly curved path, and then exits from the other side. Only the thin layer of gas near the surface of the sensitive material can truly adhere to the surface of the sensitive material and effectively participate in the adsorption or reaction, while most of the gas molecules quickly pass through the surface of the sensitive layer. For medium and high concentration gases, such contact opportunities can meet the detection requirements; but when the concentration of the target gas drops to the ppb level, the number of molecules that can truly participate in adsorption or reaction and thus cause resistance changes is very limited, and the response signal is very weak, which seriously restricts the sensitivity and detection limit of the sensor.

[0004] From the perspective of electronic noise, even in a zero-gas environment such as pure nitrogen or pure air, resistance-type gas sensors also have unavoidable background noise, which comes from the thermal motion of charge carriers in the sensitive material, the instability of the electrode contact interface, power supply ripple, and electromagnetic interference between the circuit board and the surrounding environment. When the concentration of the target gas drops to the ppb level, the effective signal amplitude of the sensor output is often comparable to or even smaller than the noise amplitude. If only relying on increasing the amplification factor, only the signal and noise will be amplified simultaneously, which has limited help for improving the signal-to-noise ratio, making it difficult to break through the detection limit.

[0005] In addition, the conventional substrate is mostly rigid ceramic or glass material, and it is difficult to process into a structure with complex three-dimensional space airflow channel; if simply using ordinary plastic material, there are problems of insufficient chemical resistance, easy aging or slow release of small organic molecules in VOCs environment, which is very unfavorable for trace gas detection. Many existing devices also need to use structural adhesive or double-sided adhesive for bonding when assembling flexible electrodes, and these adhesives will continuously release a small amount of volatile organic compounds during curing and long-term use, which constitutes potential background interference for low-concentration VOCs detection. SUMMARY

[0006] Therefore, the purpose of the present application is to provide a gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure, which improves the contact efficiency of gas and sensitive surface in a limited volume through the improvement of sensor structure, process and system circuit, simultaneously completes three-dimensional assembly and gas-sensitive membrane growth in a stable and clean way, and improves the signal-to-noise ratio through the combination of multiple sensing units, thereby greatly improving the detection sensitivity of the sensor to trace VOCs (i.e., reducing LoD).

[0007] In order to achieve the above-mentioned purpose, the specific technical solutions adopted by the present application are as follows:

[0008] A gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure, which is characterized by comprising a three-dimensional biomimetic spiral staircase substrate, a flexible electrode attached to the inner wall of the three-dimensional biomimetic spiral staircase substrate, and a gas-sensitive thin film deposited on the surface of the flexible electrode.

[0009] Optionally, the structure of the three-dimensional biomimetic spiral staircase substrate is generated by a parameterized equation, wherein the value range of the space trajectory parameter s is 0 , the radius r = a + (b-a)s , a < b, and the coordinate functions of x, y and z are respectively:

[0010] x = r·cos(s), y = r·sin(s), z = cs / π

[0011] wherein represents the rotation angle of the spiral curve around the z axis; a represents the initial radius of the spiral curve at the starting point (s = 0, z = 0); b represents the final radius of the spiral curve at the terminal point (s = , z = cs / π); c is a scaling constant for determining the stretching ratio or climbing rate of the spiral curve in the vertical direction (z axis direction).

[0012] The entity spiral structure is obtained by copying two curves with a height difference of h in the z direction, and then symmetrically arranging the material thickness d in the normal direction, and h and d are both greater than 0.

[0013] Optionally, the three-dimensional biomimetic spiral stepped substrate is formed by fused deposition modeling, 3D printing, injection molding, compression molding, or CNC machining using polyethylene terephthalate modified material.

[0014] Optionally, the flexible electrode includes an insulating substrate, on which a conductive material is deposited and etched to form an electrode. Non-conductive sidebands for connecting the three-dimensional biomimetic spiral stepped substrate are reserved on both sides of the insulating substrate. The gas-sensitive thin film is deposited on the electrode, and the conductive material is typically copper.

[0015] Optionally, a fixing through hole is provided at the corresponding position on the non-conductive side strip and the three-dimensional biomimetic spiral stepped substrate, and the flexible electrode is fixed on the three-dimensional biomimetic spiral stepped substrate by a tie wire inserted in the fixing through hole.

[0016] Optionally, the insulating substrate is made of polyethylene terephthalate, and the flexible electrode is an interdigitated electrode with the same finger width and finger spacing.

[0017] Optionally, the gas-sensitive film is a MOF gas-sensitive film. The specific type and deposition ratio of MOF can be flexibly selected according to the type of target gas and performance requirements. For example, Cu can be used. 2+ Ni 2+ Co 2+ Conductive MOF materials with metal ions as nodes and polyhydroxy aromatic ligands as organic framework.

[0018] Optionally, the gas-sensitive thin film is formed by a layer-by-layer self-assembly deposition method through eight rounds of deposition.

[0019] Optionally, multiple gas-sensitive sensors are connected in parallel, with their positive terminals all connected to the positive terminal of a constant voltage source, and their negative terminals all connected to the negative terminal of the constant voltage source after passing through a current detection terminal. When the target gas is present, the response current of each sensor increases in the same direction, and the total signal is approximately N times the signal of a single sensor. Meanwhile, the noise in each branch is independent, and the total noise amplitude is approximately [a fraction of] the noise of a single sensor. This is several times, thus the signal-to-noise ratio of the array is approximately one-third that of a single unit. The overall detection limit can be calculated as 1 / The proportion decreased.

[0020] The beneficial effects of this invention are:

[0021] (1) By using a parameterized three-dimensional biomimetic spiral stepped substrate, the flow path of the gas to be measured in the gas chamber is forcibly changed, so that the gas can circle around the spiral path multiple times within a limited height, and the gas molecules can pass over the sensitive area multiple times, which greatly increases the effective contact opportunity with the gas-sensitive membrane, thereby improving the gas-sensitive material's ability to capture trace low concentration VOCs in terms of structure.

[0022] (2) The flexible electrode plate is tightly bonded to the three-dimensional biomimetic spiral step substrate by mechanical fixation. No adhesive is used in the entire assembly process, which avoids background interference of the slow release of small organic molecules during the curing and aging of glue on trace gas detection.

[0023] (3) MOF thin films are deposited using a layer-by-layer self-assembly process. Only a very thin layer of material is grown in each cycle. The film thickness is precisely controlled by the number of repetitions. A continuous, dense and well-adhesive gas-sensitive layer can be obtained on a complex spiral surface, ensuring consistency between batches.

[0024] (4) By connecting multiple three-dimensional biomimetic spiral step sensors in parallel, the overall signal-to-noise ratio is improved and the detection limit is reduced in a statistical sense, so as to achieve a lower LoD for trace VOCs without changing the material and structure of a single device.

[0025] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0027] Figure 1 A schematic diagram of the three-dimensional structure of a three-dimensional biomimetic spiral stepped substrate provided for a specific embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the planar structure of a flexible interdigitated electrode plate;

[0029] Figure 3 A schematic diagram of the process for container cleaning, solution preparation, and low-temperature plasma treatment before the preparation of Cu3(HHTP)2 gas-sensitive thin films;

[0030] Figure 4 This is a schematic diagram of the layer-by-layer self-assembly deposition process;

[0031] Figure 5 A schematic diagram showing the setup of the test platform;

[0032] Figure 6 The linear fitting results of a single three-dimensional biomimetic spiral step gas sensor in Example 1 within the range of 1–20 ppm NH3;

[0033] Figure 7This is a schematic diagram of the theoretical circuit connection topology of multiple gas sensors connected in parallel in Example 2. Detailed Implementation

[0034] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the preferred embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0035] Example 1:

[0036] like Figure 1 and Figure 2 As shown, this embodiment proposes a gas-sensitive sensing device based on a three-dimensional biomimetic spiral stepped structure, including a three-dimensional biomimetic spiral stepped substrate, a flexible electrode attached to the inner wall of the three-dimensional biomimetic spiral stepped substrate, and a gas-sensitive thin film deposited on the surface of the flexible electrode.

[0037] pass Figure 1 As can be seen, the three-dimensional biomimetic spiral stepped substrate in this example exhibits a spiraling upward shape along the height direction, resembling a "three-dimensional biomimetic spiral staircase" spiraling around a central axis. Its geometry is controlled by parameter s, forming two spiral guides with different heights. A "lofting" operation is performed using these two curves as boundaries to obtain a spiral ribbon surface. Finally, a thickness of 1 mm is added along the normal direction of the surface to form a three-dimensional biomimetic spiral stepped substrate with solid wall thickness. Software calculations show that in this example, the spatial trajectory parameter s ranges from 0 to 4π, the spiral radius r = 1.8 + (2.0713288s) / π, and the coordinate functions in the x, y, and z directions are: x = r·cos(s), y = r·sin(s), z = 3s / π. The height difference h between the two spiral curves in the z direction is 14 mm, and the unfolded length of the central path is approximately 70.135 mm. This means that within a relatively limited height range, a relatively long travel path and multiple loops of structure are provided for the gas.

[0038] In the forming stage, this embodiment preferably uses white polyethylene terephthalate (PETG) modified material as the three-dimensional biomimetic spiral step substrate material. The above three-dimensional model is exported as an STL file and printed on a 3D printer. The printing parameters include a layer height of 0.1 mm, a fill rate of 100%, a nozzle temperature of approximately 240°C, and a heated bed temperature of approximately 70°C to ensure that the formed part has high mechanical strength and good dimensional accuracy. After printing, the support is removed and the spiral surface is polished to eliminate obvious steps and burrs, making the surface smoother to facilitate the subsequent bonding of flexible electrodes. Figure 1 A through hole with a diameter of about 0.5 mm is drilled at the location indicated by the red circle to facilitate the subsequent threading and fixing of the flexible electrode.

[0039] then, Figure 2 A planar structural design diagram of the flexible electrode is provided. In this embodiment, the flexible electrode used is an interdigitated electrode, employing transparent polyethylene terephthalate (PET) as the insulating substrate. Copper is deposited on its surface, and the interdigitated electrode pattern is formed through etching. The electrode fingers are arranged in parallel and staggered patterns, with a finger width and spacing of 0.1 mm, thus arranging multiple fingers within an effective width of approximately 6.4 mm, maximizing the sensitive area. To improve the corrosion resistance and interface stability of the copper surface, this embodiment preferably performs immersion gold treatment on the copper surface after etching, forming a thin gold layer on the copper electrode surface with a thickness of approximately 50.8 nm. The flexible electrode board is cut into a strip of 70.135 mm × 14 mm, with the central area of ​​approximately 68.13 mm designated as the interdigitated electrode area, and the two ends as solder pad areas. Figure 2 The shaded areas represent the two side strips, which are transparent PET areas without copper plating, i.e., non-conductive side strip areas used for mechanical fixing.

[0040] During the assembly stage, Figure 2 The flexible electrode plate shown starts from one end along... Figure 1 The three-dimensional biomimetic spiral stepped substrate shown is slowly bent so that the electrode surface faces outwards. The electrode-free area on the back of the circuit board is in close contact with the surface of the three-dimensional biomimetic spiral stepped substrate, and the corresponding transparent edge strip is aligned with the through holes pre-drilled on the side of the spiral substrate. Then, a thin metal wire is taken and passed through each through hole and the corresponding transparent edge strip in sequence, and then tightened on the back of the substrate to form a fixed structure similar to a suture. This wire-threading and tightening operation is performed hole by hole along the length direction, so that the flexible electrode plate is tightened and fixed at multiple points on the spiral surface.

[0041] After mechanically fixing the flexible electrode plate, in order to prepare a Cu3(HHTP)2MOF thin film with gas-sensitive function on the electrode surface, the following processes are required before film preparation: container cleaning, low-temperature plasma treatment, and solution preparation. (See [link to documentation]). Figure 3 In this embodiment, the relevant glassware and assembled components are first cleaned. Specifically, three 125mL wide-mouth borosilicate glass bottles are selected as containers for the metal source solution, ligand source solution, and assembled components, and a 100mL graduated cylinder is prepared. Acetone, anhydrous ethanol, and deionized water are poured into these glasswares in sequence, and each is ultrasonically cleaned for about 10 minutes to thoroughly remove oil and dust.

[0042] Then, the surface of the assembled device is subjected to low-temperature plasma treatment. Specifically, the assembled device is placed in the chamber of a low-temperature plasma cleaner, the chamber door is closed, and a vacuum is drawn to a preset value of 0.024 kPa. The gas inlet channel is opened to allow a gas flow rate of approximately 200 mL / min, and the power is set to 200 W. The device surface is then subjected to low-temperature plasma treatment for approximately 120 seconds. During the treatment, hydroxyl groups are introduced into the electrode surface, changing the surface from a relatively hydrophobic state to a hydrophilic state, making it easier to be wetted and adsorbed by subsequent solutions. After the treatment, the gas flow is stopped, the vacuum is removed, and the pressure is increased to atmospheric pressure by clicking "Vent". The chamber door is then opened, and the treated three-dimensional biomimetic spiral step sensor is removed. Next, using an analytical balance, 19.965 mg of Cu(OAc)₂·H₂O powder and 3.245 mg of HHTP powder were weighed separately. Then, 100 ml of anhydrous ethanol was added to each, and the mixture was sonicated for approximately 10 minutes until completely dissolved, yielding 0.1 mM Cu(OAc)₂ ethanol solution and 0.01 mM HHTP ethanol solution. Both solutions were temporarily stored at a constant temperature of 40°C for later use. Thus, Figure 3 The "cleaning-plasma treatment-liquid preparation" section has been completed.

[0043] Next, we enter the layer-by-layer self-assembly deposition stage, see [link / reference] Figure 4 , Figure 4 A schematic diagram of the overall process flow for alternating immersion with metal and ligand sources is provided. After the Cu(OAc)₂ ethanol solution and HHTP ethanol solution have been prepared and the device surface has been treated, the device is immersed in the 40℃ Cu(OAc)₂ ethanol solution for 10 minutes in the first round to allow copper ions to be fully adsorbed on the electrode and its surrounding surface. The device is then removed and rinsed in another glass bottle containing anhydrous ethanol for about 1 minute to remove unbound free copper ions, followed by drying with high-purity N₂ for about 30 seconds. Next, the device is immersed in the 40℃ HHTP ethanol solution for 20 minutes in the first round to allow the organic ligands to coordinate with the surface copper ions and grow an initial Cu₃(HHTP)₂ framework. After immersion, ethanol rinsing and N₂ drying are performed again. This completes the first metal-ligand source cycle. In cycles 2-8, the immersion time in the Cu(OAc)₂ ethanol solution is shortened to 5 minutes, and the immersion time in the HHTP ethanol solution is shortened to 10 minutes, while the other steps remain unchanged. After eight rounds of alternating immersion, the Cu3(HHTP)2 film on the electrode surface gradually thickened and became denser and more uniform. Finally, the device was placed in a vacuum chamber and dried at room temperature for 20 hours to allow residual solvent inside the film to evaporate completely and the structure to stabilize. Visual observation revealed that the interdigitated electrode area appeared deep blue and uniformly distributed against a white spiral substrate background, indicating that the gas-sensitive film had been successfully applied. Figure 2 On the electrode region of the structure shown.

[0044] After the sensor was fabricated, in order to evaluate its response performance to NH3 at room temperature, this embodiment constructed a system as follows: Figure 5 The test platform shown. Figure 5 A schematic diagram of the entire test gas path and electrical signal acquisition system is provided. It can be seen that the gas source section includes a high-purity nitrogen collection bag and multiple pre-prepared standard mixed collection bags of NH3 at different concentrations (1, 3, 5, 10, 20 ppm). By switching valves, one collection bag or N2 of a specific concentration is selected and connected to the inlet of a single MFC (Medium-to-Fuel Cell). The MFC is responsible for stabilizing the single-path gas flow at 1000 sccm. The MFC outlet is connected to a Teflon chamber via a Teflon hose. The chamber contains the three-dimensional biomimetic spiral step gas sensor prepared in this embodiment. Simultaneously, the sensor is connected to an external circuit via leads and is positioned in the airflow path in the middle of the chamber. The sensor electrodes are led out through sealed electrode holders and connected to a digital multimeter. The multimeter outputs the measured resistance value to a host computer for recording and processing.

[0045] On this testing platform, this embodiment follows a three-stage process of "N2 baseline - NH3 injection - N2 cleaning" to test each concentration point. Taking 1 ppm NH3 as an example, firstly, the MFC inlet is connected to a high-purity N2 collection bag, and the flow rate is set to 1000 sccm, allowing pure N2 to be collected... Figure 5 The sample was flowed in the Teflon chamber for 2 minutes to establish a stable baseline. The host computer recorded the resistance fluctuations during this period and calculated the noise standard deviation. Then, the MFC inlet was switched to a 1 ppm NH3 standard gas collection bag, maintaining a flow rate of 1000 sccm. After entering the chamber, the NH3 interacted with the Cu3(HHTP)2 thin film, causing a change in the sensor resistance. The injection was stopped after 10 minutes. The MFC inlet was then switched back to high-purity N2, and 1000 sccm of N2 was introduced for approximately 20 minutes of rinsing to restore the resistance to near the initial baseline. Following the same procedure, different concentrations of NH3 (1, 3, 5, 10, and 20 ppm) were tested one by one. A complete resistance-time curve was recorded for each concentration point, and the response calculation formula was... ,in This represents the average resistance of samples injected in the last minute. This represents the average resistance of the baseline in the last minute.

[0046] Finally, a linear fit was performed between the steady-state response values ​​at different concentrations and the NH3 concentration to obtain the results. Figure 6 . Figure 6 The fitted line, slope, and correlation coefficient R are given. 2The lowest detection limit (LoD) calculated using the formula "LoD = 3σ / slope" is 36.61 ppb. Specifically, the linear fitting correlation coefficient in this embodiment is close to 0.93, indicating that the sensor has a good linear response to NH3. In summary, Figures 1 to 6 The presented structure, process flow, and experimental data fully demonstrate the superiority of the sensor's specific construction and actual performance in this embodiment.

[0047] Example 2

[0048] Based on the structure and performance of a single three-dimensional biomimetic spiral step gas sensor obtained in Example 1, this example further combines... Figure 7 This paper analyzes the potential advantages of parallel multi-sensor connections in reducing detection limits from a theoretical perspective.

[0049] Figure 7 A circuit topology diagram showing N gas sensors connected in parallel at their gas-sensitive resistor terminals is provided. It can be seen that... Figure 7 In the diagram, several rectangles represent individual gas sensors, and each rectangle is equivalent to a gas-sensitive resistor. One end of all sensors is connected to the positive terminal of the constant voltage power supply Vs, and the other end is connected to the input terminal of the current detection module (such as an ammeter or current measurement circuit), forming a parallel network consisting of N branches. Figure 7 The Iout indicated by the middle arrow is the total output current of the entire array.

[0050] Assuming each sensor is a three-dimensional biomimetic spiral ladder sensor fabricated with the same structure and process as in Example 1, with essentially identical performance, the average current under zero gas (pure nitrogen) or pure air conditions is approximately the same, I0, and the standard deviation of random noise is approximately σ. Under a fixed NH3 concentration, the average current increase of a single sensor is ΔI. According to the principle of parallel circuits, in the presence of NH3, the total signal current increase of N sensors is equal to the sum of the increases in each branch, i.e., the total signal current is approximately N × ΔI. As for the noise current, assuming the noise sources in each branch are independent and uncorrelated, the variance of the total noise is approximately N times the variance of the noise of a single sensor, i.e., Nσ², corresponding to a standard deviation of approximately... ×σ. This means that when N sensors are connected in parallel, the total signal amplitude increases linearly with N, but the total noise amplitude only increases linearly with N. The rate of growth.

[0051] From this, we can obtain Figure 7 The total signal-to-noise ratio (SNR) of the array shown is approximately (N×ΔI) / ( ×σ)≈ ×(ΔI / σ), which is the signal-to-noise ratio (SNR) of a single sensor (Single). The minimum detection limit (LoD) is inversely proportional to the signal-to-noise ratio (SNR), meaning LoD is directly proportional to 1 / SNR. Therefore, the overall detection limit of the array (LoD_array) is approximately equal to the detection limit of a single sensor (LoD_single) divided by [the value of LoD]. The method used in Example 1... Figure 6 Substituting the calculated LoD_single ≈ 36.61 ppb into the relationship, we can obtain the theoretical detection limit for several typical array sizes. For example, when 1000 sensing units are connected in parallel in a sensing array configuration, the theoretical detection limit can be reduced to below approximately 1.2 ppb. Although in practical applications, factors such as device consistency, circuit noise, and airflow distribution within the chamber need to be considered, and the theoretical and actual values ​​may deviate to some extent, Figure 7 The parallel circuit model shown clearly demonstrates the different superposition rules of signal and noise in the array structure, illustrating that increasing the number of sensors can statistically lower the detection limit, providing a design basis for building a multi-sensor electronic nose system in the future.

[0052] As can be seen from the detailed description of the invention and its embodiments above, this invention, by employing a parameterized three-dimensional biomimetic spiral stepped substrate, flexible interdigitated electrode mechanical fixation, and MOF gas-sensitive thin film layer-by-layer self-assembly process, effectively extends the gas flow path near the sensitive area at the structural level, significantly increasing the contact opportunities between VOCs molecules and the gas-sensitive film; at the process level, it avoids potential pollution sources such as adhesives, and the introduced MOF thin film can still maintain good uniformity and adhesion on the three-dimensional curved surface; at the system level, through the parallel structure of multiple sensors, it statistically improves the signal-to-noise ratio, enabling the overall detection limit to be reduced to 1 / The rate of decrease is consistent with the actual test in Example 1. The actual test further shows that, with Cu3(HHTP)2 MOF gas-sensitive membrane and NH3 as the test objects, a single three-dimensional biomimetic spiral step sensor achieved a LoD of 36.61 ppb, which verifies the effectiveness of the three-dimensional biomimetic spiral step structure in improving the sensitivity of trace gas detection.

[0053] It should be noted that the embodiments given in this specification are merely specific examples of the technical solutions of the present invention, intended to facilitate understanding of the present invention by those skilled in the art, and do not constitute a limitation on the scope of protection of the present invention. After reading this specification, those skilled in the art can make various equivalent modifications or improvements to the three-dimensional biomimetic spiral stepped geometric parameters (such as radius increment, number of spiral turns, axial height difference), substrate material (such as other engineering plastics, ceramics or metal materials), electrode form (such as changing line width, line spacing, material or number of layers, interdigitated electrodes or space-filling geometric curve electrodes, etc.), MOF gas-sensitive material type (such as selecting other metal centers and organic ligand combinations), and test gas type (such as NO2, H2S and various VOCs mixed gases), array size and circuit topology, without departing from the overall concept and core idea of ​​the present invention. As long as the technical effect is the same as or similar to that of the present invention, that is, it still enhances the contact between the gas and the sensitive surface through the three-dimensional biomimetic spiral stepped geometric structure and reduces the detection limit through the array method, it should be considered to fall within the scope of protection of the present invention.

Claims

1. A gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure, characterized in that, It includes a three-dimensional biomimetic spiral stepped substrate, a flexible electrode attached to the inner wall of the three-dimensional biomimetic spiral stepped substrate, and a gas-sensitive thin film deposited on the surface of the flexible electrode.

2. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 1, characterized in that, The structure of the three-dimensional biomimetic spiral stepped substrate is generated through a parametric equation, wherein the spatial trajectory parameter s ranges from 0 to... , radius r=a+(ba)s / If a < b, the coordinate functions in the x, y, and z directions are as follows: x = r·cos(s), y = r·sin(s), z = cs / π; in, denoted by , a represents the rotation angle of the helical curve around the z-axis; denoted by a, a represents the initial radius of the helical curve at the starting point; denoted by b, a represents the final radius of the helical curve at the ending point; denoted by c, a scaling constant used to determine the scaling ratio or climbing rate of the helical curve in the vertical direction. By copying two curves with a height difference of h in the z-direction and performing lofting, and then symmetrically setting the material thickness d along the normal direction, a solid spiral structure is obtained, where both h and d are greater than 0.

3. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 1 or 2, characterized in that, The three-dimensional biomimetic spiral stepped substrate is formed by fused deposition modeling, 3D printing, injection molding, compression molding, or CNC machining using polyethylene terephthalate modified material.

4. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 1 or 2, characterized in that, The flexible electrode includes an insulating substrate, on which a conductive material is deposited and etched to form an electrode. Non-conductive sidebands for connecting the three-dimensional biomimetic spiral stepped substrate are reserved on both sides of the insulating substrate. The gas-sensitive thin film is deposited on the electrode.

5. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 4, characterized in that, Fixed through holes are provided at corresponding positions on the non-conductive side strip and the three-dimensional biomimetic spiral stepped substrate, and the flexible electrode is fixed on the three-dimensional biomimetic spiral stepped substrate by tie wires inserted in the fixed through holes.

6. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 5, characterized in that, The insulating substrate is made of polyethylene terephthalate, and the flexible electrode is an interdigitated electrode with the same finger width and finger spacing.

7. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 1, 5, or 6, characterized in that, The gas-sensitive film is a MOF gas-sensitive film.

8. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral stepped structure according to claim 7, characterized in that, The gas-sensitive thin film was formed by a layer-by-layer self-assembly deposition process through eight rounds of deposition.

9. The gas-sensitive sensing device based on a three-dimensional biomimetic spiral staircase structure according to claim 1 or 8, characterized in that, Multiple gas-sensitive sensors are connected in parallel, with their positive terminals all connected to the positive terminal of a constant voltage source, and their negative terminals all connected to the negative terminal of the constant voltage source after passing through a current detection terminal.

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