A high-sensitivity microstructure gas sensor based on a three-cantilever structure

Abstract

A high-sensitivity microstructure gas sensor based on a three-beam structure includes a central region with a gas-sensitive material. The central region is connected to a surrounding substrate layer by three cantilever beams. Apart from being connected by the cantilever beams, the central region does not contact the surrounding substrate layer. The cantilever beams are constructed as porous structures, with a first end connected to the central region and a second end connected to the substrate layer. The cantilever beams are arranged such that the aperture and the spacing between the apertures gradually change from the first end to the second end.

Description

Technical Field

[0001] This invention relates to the field of gas sensing, and more particularly to a high-sensitivity microstructure gas sensor based on a three-beam structure. Background Technology

[0002] CN210626385U discloses a resistive semiconductor gas sensor with a four-support cantilever structure. The sensor structure, from bottom to top, includes: a silicon substrate layer with a central groove serving as a heat-insulating cavity; a support layer comprising support cantilever beams and an insulating region, the insulating region being located above the heat-insulating cavity of the silicon substrate layer and connected to the silicon substrate layer via four support cantilever beams; an electrode layer comprising heating electrodes, interdigitated electrodes, power supply leads, and test leads, the heating electrodes being arranged in a zigzag pattern on both sides of the insulating region and connected to the power supply leads; interdigitated electrodes being distributed in the center of the insulating region and connected to the test leads; and a gas-sensitive layer covering the interdigitated electrodes and electrically connected to them. This invention features low power consumption and good thermal insulation. Furthermore, temperature control is more efficient, avoiding short circuits between the interdigitated electrodes and the heating electrodes caused by the loading of low-resistivity gas-sensitive materials.

[0003] CN102288644A relates to a resistive gas sensor with a four-supported cantilever, four-layer structure and its fabrication method. The sensor structure includes: a substrate frame, a heat insulation cavity, a heating film region, supporting cantilever beams, heating resistance wires, power supply leads, power supply electrodes, interdigitated electrodes, detection leads, detection electrodes, and a sensitive membrane. Its structural features are as follows: the heating film region, located above the heat insulation cavity, is connected to the substrate frame via four supporting cantilever beams; the heating resistance wires are arranged in a zigzag pattern on the heating film region and are connected to the power supply electrodes on the substrate frame via power supply leads; the interdigitated electrodes are arranged in the gaps between the heating resistance wires and are connected to the detection electrodes via detection leads; the sensitive membrane is located on the heating film region, covering the entire heating resistance wires and interdigitated electrodes and having good electrical connection with the interdigitated electrodes.

[0004] Metal oxide gas sensors based on ceramic plates suffer from high power consumption, poor material consistency, and low production efficiency due to the use of traditional coating methods for material loading. For metal oxide gas sensors based on microstructure technology, the gas-sensitive materials prepared by chemical methods are difficult to load onto the micro-hot plate, and the material consistency is also poor. On the other hand, gas-sensitive materials can be directly prepared on the micro-hot platform using semiconductor processes such as sputtering and evaporation, but the dense surface structure of these materials significantly reduces their response and sensitivity.

[0005] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0006] Existing gas sensors typically require specific temperature conditions to function properly. Therefore, increasing and maintaining heat accumulation in the sensing area is crucial for reducing the energy consumption of gas sensors. For example, patent document CN108519408A discloses a gas sensor, a method for fabricating the sensor, and a sensor array. The sensor includes a silicon substrate, a detection electrode, a first insulating film, a heating resistor, and a second insulating film stacked sequentially. It features a substrate structure and a cantilever structure with freely curled ends, with a gas-sensitive material at the end of the cantilever structure. This technical solution employs a single cantilever beam structure, placing the effective area at the end of the cantilever beam. By reducing the effective area area and the number of cantilever beams, the sensor's power consumption is reduced. However, the curled structure of this sensor increases its overall size, making it unsuitable for applications requiring miniaturization and planarization in detection environments. This technical solution is also completely opposite to the planar structure of the standard chip sensor used in this invention. To address the shortcomings of existing technologies, this invention provides a high-sensitivity microstructure gas sensor based on a three-beam structure. The sensor includes a central region containing a gas-sensitive material. The central region is connected to a surrounding substrate layer via three cantilever beams. Apart from being connected by the cantilever beams, the central region does not contact the surrounding substrate layer. The cantilever beams are constructed as porous structures, each having a first end connected to the central region and a second end connected to the substrate layer. The cantilever beams are arranged such that the aperture and spacing gradually change from the first end to the second end.

[0007] Compared to the prior art, the central region in this invention can be connected to the substrate layer via a cantilever beam, and an adiabatic heat transfer path is formed by setting a specific cantilever beam structure. Based on the above-mentioned distinguishing technical features, the technical problem to be solved by this invention is how to reduce heat loss from the cantilever beam structure. Specifically, the prior art uses a cantilever beam structure with a curled structure for the effective area of ​​loading the gas-sensitive material, and positions it at the end of the cantilever beam structure away from the base structure. On the one hand, by reducing the area of ​​the effective region, heat loss caused by thermal convection and thermal radiation is reduced; on the other hand, the cantilever beam structure is thin and long, and curves upward, avoiding contact with the silicon substrate, thereby significantly reducing heat loss during heat conduction, and thus the sensor has extremely low power consumption. In other words, this technical solution mainly reduces heat loss through the spatial configuration and length of the cantilever structure. The insulation component is significantly different from the technical solution of this application. This technical solution still requires a sufficiently long supporting cantilever structure to achieve sufficient insulation effect. Furthermore, the single cantilever structure will increase the cantilever length by several times compared to the multi-cantilever structure, thereby significantly increasing the size of the gas sensor. This is extremely detrimental to the miniaturization and micro-miniaturization of gas sensors.

[0008] Currently, for the design of micro-sized gas sensor structures, in order to simultaneously meet the requirements of heat accumulation and structural strength, it is common to adopt a multi-beam structure to connect the sensing area and the non-sensing area. For example, patent document CN210626385U discloses a resistive semiconductor gas sensor with a four-support cantilever structure. This sensor structure, from bottom to top, includes a silicon substrate layer with a groove in the middle serving as a heat insulation cavity, and a support layer including support beams and an insulating region. The insulating region is located above the heat insulation cavity of the silicon substrate layer and is connected to the silicon substrate layer by four support beams. However, this technical solution's cantilever structure can create some hollow areas between the sensing area and the non-sensing area. The heat accumulation in the sensing area is ensured by the insulating properties of the air in the hollow areas, essentially creating a heat insulation region through the air environment inside the groove. This groove structure requires sufficiently long support beams to meet the corresponding strength requirements, which is why the support beams are placed on a sufficiently large silicon substrate layer for connection. Existing technologies merely use a cantilever structure to achieve the above objectives. However, further research in this scheme revealed that the cantilever beam possesses certain thermal conductivity properties. Therefore, to further optimize energy resource utilization, the cantilever beam must meet a certain length to achieve sufficient thermal insulation. On the one hand, this increases the area of ​​individual sensors, reducing the integration of the combined sensor circuit. On the other hand, increasing the length of the cantilever beam is detrimental to the stability of the overall structure, making it more vulnerable to impacts or stresses. Therefore, unlike existing technologies, this scheme further investigates the specific design of the cantilever beam. The cantilever beam structure designed according to this scheme can still have a sufficiently short cantilever beam length that meets the requirements of high integration and structural strength while ensuring sufficient thermal insulation length. This significantly improves the integration, energy utilization, and structural strength of the sensing device. Specifically, this invention adjusts the thermal conductivity rate of the cantilever beam structure by setting the cantilever beam with gradually varying aperture and aperture spacing from the first end to the second end. This creates a gradient thermal conductivity rate arrangement on the cantilever beam, forming a multi-level thermal buffer barrier to slow down heat loss and reduce the overall energy consumption of the gas sensor.

[0009] Preferably, the hole structure on the cantilever beam is arranged in a manner that gradually increases in diameter from the first end to the second end. The first end and / or the portion near the first end are configured with relatively small and densely arranged holes, while the second end and / or the portion near the second end are configured with relatively large and relatively dispersed holes. Compared with the prior art described above, the specific arrangement of the hole diameter on the cantilever beam of the present invention differs. Based on the aforementioned distinguishing technical features, the technical problem to be solved by the present invention is how to reduce the thermal conductivity of the cantilever beam structure. Specifically, this solution sets the hole diameter on the cantilever beam in a manner that gradually increases from the first end to the second end, thereby creating a greater gradient in the thermal conductivity rate near the first end of the cantilever beam, which is closer to the central region, and thus significantly reducing the rate of heat transfer. Furthermore, by forming a larger and relatively dispersed hole structure near the second end of the cantilever beam, which is farther from the central region, sufficient buffer space is provided for the heat introduced from the first end. Only after this buffer space is gradually occupied by the transferred heat does heat transfer proceed to the next larger buffer space, thereby further reducing the thermal conductivity rate.

[0010] Preferably, when the apertures of the cantilever beam are set with varying gradients at various points, the transverse width of the cantilever beam gradually increases from the first end to the second end.

[0011] Preferably, the negative side of the substrate layer is provided with a heating electrode by evaporation or sputtering, and the heat source coverage area of ​​the heating electrode is the area of ​​the central region.

[0012] Preferably, a detection electrode for detecting changes in the electrical parameters of the catalyst layer is superimposed on the catalyst layer disposed on the surface of the substrate layer, and the detection coverage area of ​​the detection electrode is the area of ​​the central region.

[0013] Preferably, when the filling member is filled into the partition space, it establishes a physical connection with all contact surfaces in the partition space, so that the compressive / tensile / bending forces generated on the cantilever beam along its axial and / or radial directions can be dispersed by the deformation of the filling member itself.

[0014] Compared with the prior art, the cantilever beam in this invention has a partition space, and the partition space is filled with a filling component different from the cantilever beam. Based on the above-mentioned distinguishing technical features, the technical problem to be solved by this invention is how to improve the structural strength and thermal conductivity of the gas sensor cantilever beam at different operating temperatures. Specifically, on the one hand, in order to maintain the structural strength of the connection between the central area and the base layer, and on the other hand, in order to improve the heating efficiency of the central area through heat transfer, the conventional connection structure between the central area and the base layer in the prior art usually has the same structural width or thickness as the base layer or the central area. The larger the structural surface area, the more heat is lost, and the ability to maintain heat in the core monitoring area is reduced, which also leads to an increase in the overall power consumption of the gas sensor. Specifically, the filling member of the present invention reinforces the yield strength of the cantilever beam. Observing from the axial direction of the cantilever beam, it is initially affected by the thermal expansion or contraction of the central area. Originally, the cantilever beam would be subjected to compressive or tensile forces in its axial direction, which is detrimental to the strength of the cantilever beam itself. However, due to the introduction of the filling member, its ductility and the stress release of the partition space itself, the filling member forms a buffer against the aforementioned compressive or tensile forces. This reduces the impact of thermal expansion and contraction of the central area on the compression or tension of the cantilever beam, greatly helping to ensure the strength of the cantilever beam and prevent it from breaking. Furthermore, based on this, the width of the cantilever beam can be further reduced to further decrease the channels for heat loss, which is very beneficial for heat preservation of the central area. Furthermore, from a radial perspective, since the aforementioned filling component blocks most of the heat transfer within the cantilever beam, the axial temperature gradient distribution difference along the cantilever beam will be further reduced. In fact, if the thermal conductivity of the selected filling component is sufficiently low, the temperature distribution difference will be reduced to a negligible level. This ensures that the radial yield strength of each part of the cantilever beam will not be differentiated due to temperature differences, eliminating any "weak points" in the cantilever beam. The overall strength of the cantilever beam is further enhanced, enabling it to more readily cope with the strong yielding effects of impacts. This ensures that the sensor can be used normally in environments with significant vibrations, thus expanding the applicability of the device.

[0015] Preferably, the substrate layer is composed of a porous ceramic material.

[0016] Preferably, the catalyst layer is composed of a catalyst material capable of reacting with a specific gas and a catalytic material capable of catalyzing the reaction, wherein the catalytic material is a noble metal catalytic material.

[0017] Preferably, the noble metal catalytic material is doped onto the catalyst material.

[0018] Preferably, the noble metal catalyst is obtained by drop-coating a pretreated H[PtCl] aqueous solution onto the sensing area and then heating it.

[0019] Preferably, in the case of several adjacent intermediate regions, a connecting member is provided, which is configured to connect the heat source center of one of at least two adjacent or non-adjacent intermediate regions to the heat retreat edge of the other via thermal conduction. The connecting member is capable of forming a heat transfer path between the heat source center of one of the two intermediate regions and the heat retreat edge of the other. The connecting member can be structured based on one or more of at least three heat transfer pathways, namely heat conduction, heat convection, and heat radiation, so that it can realize at least one or more of the above three heat transfer pathways. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the device structure provided by the present invention; Figure 2 This is a schematic diagram of the structure and dimensions of the central area in this invention.

[0021] In the diagram: 100, catalyst layer; 200, substrate layer; 210, central area; 220, cantilever beam; 300, detection electrode layer; 400, isolation layer; 500, heating electrode layer; 600, support layer; 700, substrate layer. Detailed Implementation

[0022] The following is in conjunction with the appendix Figures 1 to 2 Please provide a detailed explanation.

[0023] This gas sensor employs a multi-layer structure, comprising at least a substrate layer 200, a detection electrode layer 300, a catalyst layer 100, and a heating electrode layer 500. The heating electrode layer 500 is disposed below the substrate layer 200, and the detection electrode layer 300 is disposed above it. At least a portion of the space between the detection electrode layer 300 and the substrate layer 200 is sandwiched with the catalyst layer 100. In another embodiment, a detection electrode layer 300 may also be disposed below the substrate layer 200, and another detection electrode layer 300 may be disposed on the substrate layer 200, with the catalyst layer 100 sandwiched between the upper detection electrode layer 300 and the substrate layer 200. This can form a double-layer detection electrode structure, such as... Figure 1 As shown, the detection electrode layer 300 disposed on the upper layer is not shown.

[0024] This gas sensor can adopt a standard chip sensor structure, where multiple layers of gas sensors are ultimately assembled into a chip-like structure. Chip sensor structures are advantageous for mounting onto chips and can be manufactured using methods such as PCB printing, facilitating mass production in industry. MEMS, or Microelectromechanical Systems, refers to electronic devices with dimensions of a few millimeters or even smaller, integrating technologies such as photolithography, etching, thin film fabrication, silicon micromachining, and precision machining. Simply put, MEMS devices are miniature, highly integrated electronic devices. For example, the gas sensor involved in this solution has at least a core gas detection structure that is chip-sized, formed by the deposition of multiple functional layers.

[0025] The substrate 200 can be made of porous ceramic materials, such as porous alumina (AAO) or porous aluminum silicate. Porous alumina possesses a large number of uniform and parallel high-density hexagonal pore structures. Depending on the manufacturing process, the thickness of the substrate 200 can reach nanometer to micrometer levels, and the pore size can reach nanometer levels. The substrate 200 has at least two surfaces, which can be referred to as the surface and the negative surface, respectively. As mentioned above, when the gas sensor adopts a sheet structure, the substrate 200 can also be roughly configured as a sheet structure, in which case the surface and the negative surface are two opposing surfaces of the substrate 200. As described above, the substrate 200 has multiple uniform and high-density pore structures, which can form channels for gas, especially the gas being detected. Based on the adsorption properties of molecules, the molecules of the gas being detected can be adsorbed into the pores of the substrate 200, achieving temporary retention of the gas being detected and facilitating contact and reaction between the gas and the catalyst.

[0026] The catalyst layer 100 can be composed of various catalyst materials selected based on the intended target gas. The working principle of this gas sensor lies in the fact that certain catalyst materials possess gas-sensitive properties at a specific temperature. These materials can change their conductivity upon combining with a specific gas. This conductivity is typically measured using resistance or conductance as a reference value, and the change in conductivity is related to the amount of the specific gas. Therefore, the gas sensor can detect the concentration of a specific gas in the environment. Examples of such catalyst materials include, for instance, N-type semiconductors such as SnO2, ZnO, In2O3, and WO3, and P-type semiconductors such as CuO, Mn3O4, Co3O4, and NiO. Each of these catalyst materials possesses gas-sensitive properties for specific gases. Furthermore, for a single catalyst material, the structure, particle size, and other parameters can be controlled by changing the material's synthesis process. Doping and surface modification treatments can also be used to enhance the material's selectivity for a specific gas. In addition to the aforementioned catalyst material, the catalyst layer 100 also includes a catalytic material capable of catalyzing the reaction between the catalyst material and a specific gas, such as certain noble metal elements. In this embodiment, noble metal materials such as platinum and palladium are selected as the catalytic material for the catalyst layer 100. In this embodiment, the surface layer of noble metal catalytic materials such as Pt and Pd is deposited using doping technology. Alternatively, in another embodiment, the surface layer of noble metal catalytic materials such as Pt and Pd is obtained by drop-coating a pretreated H[PtCl] aqueous solution onto the sensing area and then heating it. When forming the catalyst layer 100, a catalyst material layer is first constructed using deposition technology, and then a catalytic material layer is constructed on the catalyst material layer by deposition. The two layers are combined to form the catalyst layer 100.

[0027] The detection electrode includes at least a standard electrode unit and a detection electrode unit, which are formed on the inner and outer surfaces of the substrate layer 200, respectively. At least one side of the detection electrode, containing the electrode, is disposed on the catalyst layer 100 to detect the catalyst layer 100. When the catalyst in the catalyst layer 100 comes into contact with a specific gas and a change in its electrical parameters occurs, the detection electrode, due to the electrode circuit formed at the location of the catalyst layer 100, can measure this change and further calculate the content of the specific gas based on this change data. Preferably, the detection electrode can be made of various materials, such as elemental or alloy materials of platinum, gold, rhodium, ruthenium, palladium, rhenium, titanium, etc.

[0028] The heating electrode can be configured as a structure similar to an electric heating wire. It is disposed on the negative side of the substrate layer 200 to heat the catalyst layer 100 loaded on the surface of the substrate layer 200, thereby heating the catalyst in the catalyst layer 100 to a temperature sufficient to react with the specific gas being measured. Based on research, the environmental conditions under which the catalyst reacts with a specific gas to produce a reaction that significantly alters its electrical parameters are often high-temperature conditions. Therefore, a heating electrode is needed to heat the catalyst layer 100 to a predetermined temperature. In this embodiment, the heating electrode is fabricated using an evaporation or sputtering process.

[0029] The present invention also provides a process for preparing a three-beam 220 gas sensor, comprising the following steps.

[0030] S1 prepares substrate 700, and the substrate 700 material can be silicon;

[0031] S2 has a support layer 600 on a silicon substrate, and the material can be silicon nitride / silicon oxide;

[0032] S3 has heating electrodes set on the support layer 600 using an evaporation or sputtering process;

[0033] S4 provides an isolation layer 400 on the heating electrode, such as a silicon oxide isolation layer 400;

[0034] The S5 evaporation deposition electrode can be, for example, a metallic aluminum electrode;

[0035] S6 forms the basal layer 200, which can be, for example, AAO;

[0036] S7 deposits a metal oxide gas-sensitive material on the substrate layer 200, and then does a metal catalyst material to form the catalyst layer 100 as a whole.

[0037] S8 etching of the three-cantilever 220 structure;

[0038] Preferably, to prevent a large amount of heat from being dissipated by the substrate 200 directly contacting the substrate 200 when the heating electrode utilizes the heat transfer from the heated substrate 200 to heat the catalyst layer 100 located on the surface of the substrate 200, this device is provided with a three-cantilever beam 220 structure. Specifically, an empty area is cut out of the formed substrate 200 by etching, and the empty area has at least one platform structure physically connected to the substrate 200 surrounding the empty area. According to this scheme, the platform structure has at least three cantilever beams 220, which are respectively connected from the central area 210 of the platform structure and respectively connected to the substrate 200 surrounding the empty area. The platform structure is constructed in the same way as the substrate 200. Since the etching method is used as described above, the platform structure is actually integral with the substrate 200 before etching. The width of the three cantilever beams 220 is constructed such that it does not cover the entire empty area. Preferably, to minimize heat loss, the width of the cantilever beams 220 is constructed to be smaller than the width of the central area 210. According to one example, the central region 210 is generally configured as a triangular structure. Preferably, to ensure the structural stability of the central region 210, the central region 210 can be selected as an equilateral triangular structure, such as... Figure 2 As shown. In another embodiment, the base layer 200 can also be provided with any number of cantilever beams 220, for example, one cantilever beam 220, such as... Figure 1 The example shown. However, the number of cantilever beams 220 in the base layer 200 determines the strength of the structure in the central region 210. At a very small scale, the fewer the number of cantilever beams 220, the lower the structural strength.

[0039] Basically, the three cantilever beams 220 can be connected from any position in the central region 210. Preferably, the three cantilever beams 220 are connected from the three sides of the triangular central region 210. Further, the three cantilever beams 220 are connected from the midpoints of the three sides. Alternatively and more preferably, the three cantilever beams 220 are connected from the three vertices of the central region 210, and the extensions of the three cantilever beams 220 intersect at the center of the central region 210.

[0040] Based on the above description of the structure, in the case of a three-cantilever beam 220 structure, the empty area is generally arranged around the central area 210. Essentially, at least one connected empty area is provided around the central area 210; connectivity means that this empty area is not separated by any solid material. Preferably, the empty area is arranged to surround the central area 210 such that, apart from the cantilever beams 220, no other part of the central area 210 is connected to the surrounding base layer 200. When the central area 210 is constructed as a triangle, particularly an equilateral triangle, the empty area can also be generally set to have an area larger than the central area 210, preferably a similar or identical equilateral triangle structure, and the empty area is only separated by three cantilever beams 220 extending from the central area 210. The advantage of this arrangement is that it minimizes the contact area between the central area 210 and the surrounding base layer 200 while ensuring that the central area 210 can still form a relatively stable connection with the base layer 200 through the cantilever beams 220. Based on the three thermodynamic heat transfer methods, the empty area first eliminates the prerequisite of heat conduction, which has the highest heat transfer efficiency, namely, the need for physical contact between the two, and replaces it with air, which has a relatively low thermal conductivity. This can prevent a large amount of heat loss from the central area 210. On this basis, it ensures that the power output of the heating resistor can be used almost entirely for heating the central area 210, thereby obtaining a low-power or even ultra-low-power gas sensor device.

[0041] To match the shape of the central region 210, the contact portions of the heating electrode and the detection electrode with the central region 210 are both triangular in shape, preferably equilateral triangles. Furthermore, the heating electrode can be a resistance heating element, i.e., the portion contacting the central region 210 is configured as an electric heating wire wound to match the shape of the central region 210; the detection electrode can be an interdigitated electrode, with the intersecting electrodes forming a triangular shape in the central region 210 portion.

[0042] Metal oxide gas-sensitive material is deposited on the central region 210, and noble metal catalyst material is doped onto the gas-sensitive material.

[0043] According to a preferred embodiment, this embodiment includes several adjacent sensor structures, or at least several adjacent central regions 210, and heating electrodes, catalyst layers 100, and detection electrodes disposed on the central regions 210. In this embodiment, based on the heat distribution circumferentially around a single central region 210, a connecting member is provided. The connecting member is configured to connect the heat source center of one of at least two adjacent or non-adjacent central regions 210 to the heat dissipation edge of the other via thermal conduction. Both the heat source center and the heat dissipation edge are within a specific location and are both located above the central region 210. In terms of heat distribution, the heat source center is at a higher temperature because it is in direct contact with the core heating range of the heating electrode, while the heat dissipation edge is at a relatively lower temperature because it is located at the edge of the heating electrode, further away from the core heating range. This temperature difference is detrimental to detection because it prevents the full utilization of the catalyst material in the catalyst layer 100 located above the central platform for gas detection. Furthermore, different temperature differences may cause potential imbalances on the detection electrodes, resulting in detection fluctuations. Increasing the temperature of the heating electrode to raise the temperature of the heat-retarded edge to a better reaction temperature undoubtedly increases the output power of the heating electrode, which contradicts the basic principle of establishing a low-power gas sensor. Therefore, the connecting member proposed in this embodiment is constructed to form a heat transfer path between the heat source center of one of the two central regions 210 and the heat-retarded edge of the other. Furthermore, based on thermodynamic principles, heat transfer can occur through three pathways: heat conduction, heat convection, and heat radiation. Heat conduction refers to the spontaneous transfer of heat from a higher-temperature object to a lower-temperature object through physical contact; heat convection refers to the heat transfer process caused by the relative displacement of particles in a fluid; and heat radiation refers to the transfer of heat between two objects through non-contact heat radiation.Based on the three basic heat transfer pathways mentioned above, the connecting member in this embodiment can be configured as one of the following three structures or a combination of any of them. The first is a physical connection structure based on heat conduction. In this structure, the connecting member can be made of a material with high thermal conductivity and is physically connected to the heat source center of one of the two intermediate regions 210 and the heat retraction edge of the other, thus forming a heat conduction path based on physical contact. In this case, some heat from the relatively high-temperature heat source center spontaneously enters the connecting member and causes it to heat up. When the connecting member heats up to a temperature higher than the heat retraction edge physically in contact with its other end, the heat in the connecting member spontaneously enters the heat retraction edge through heat conduction, ultimately causing the heat retraction edge to heat up. The second is a fluid passage structure based on thermal convection. In this structure, the connecting member can... One approach is to use a structure that can create a certain fluid pathway, such as a tubular structure. Gas flows through the connecting member, and because the temperature at the center of the heat source is high, the gas near the center is heated and guided to move within the connecting member, thus being transported to the heat-reducing edge, ultimately causing the heat-reducing edge to heat up. A third approach is a pathway structure based on thermal radiation. In this structure, the connecting member may not need to be in physical contact with either the center of the heat source or the heat-reducing edge. It can be designed such that the end near the center of the heat source can absorb more thermal radiation, while the end near the heat-reducing edge can release more thermal radiation. For example, different materials can be used at both ends to achieve the absorption and release of thermal radiation. Ultimately, the thermal radiation generated at the center of the heat source causes the connecting member to heat up, and the heat transferred to the heat-reducing edge by the connecting member heats up in the form of thermal radiation. Based on the above, the connecting member can be selected to achieve one or more of these three heat transfer pathways in any combination. For example, a combination of heat conduction and thermal radiation can be used to simultaneously achieve both of the above heat transfer pathways.

[0044] Different sizes can be set for different areas and different layers on the cantilever beam 220, such as aperture or density between layers. For example, the heat conduction of the cantilever beam 220 mainly comes from the heat core area of ​​the central area 210. Based on this, the aperture of the cantilever beam 220 can be set to the aperture along the central area 210 to the other end of the cantilever beam 220.

[0045] In this design, the first end connected to the central region 210 uses a dense arrangement of small holes, while the second end connected to the surrounding base layer 200 uses a dispersed arrangement of large holes. At least at the second end, the lateral width of the cantilever beam 220 is greater than that at the first end. Preferably, the width of the cantilever beam 220 gradually increases from the first end to the second end along with the gradually increasing hole diameter. Since the increased hole diameter weakens the structural strength of this part, widening the cantilever beam 220 is chosen to compensate for the reduced structural strength. Furthermore, because the increased hole diameter is located further away from the central region 210, the core heat-generating area, and the heat is blocked and retained by the densely arranged small holes closer to the first end, the lateral width can be appropriately increased in this part to ensure a certain structural strength. Therefore, in the preferred embodiment, the cantilever beam 220 can be roughly a trapezoidal structure with the first end being the short side with the upper base and the second end being the long side with the lower base, preferably an isosceles trapezoidal structure. Taking the shortest distance between the edges of two adjacent holes as the subject of discussion, the shortest distance is relatively smaller when using a dense arrangement of small holes compared to a dispersed arrangement of large holes. The shortest distance refers to the length of the shortest line connecting any two points on the edges of two adjacent holes. The advantage of this scheme is that it can be tailored to different hole structures at different locations, determining the degree of adjacency of the hole structures' boundaries while maintaining structural strength as much as possible. If larger diameter holes are too close together, it can easily lead to a decrease in structural strength, while smaller diameter holes can have their distance reduced. According to a preferred embodiment, in this embodiment, a temperature-concentrating structure based on the retention of air in the cantilever beam 220 and the form of thermal convection is set up. Specifically, by setting holes in the cantilever beam 220, the area or volume of direct physical contact between various parts of the cantilever beam 220 is reduced. Based on thermodynamic theory, heat conduction relying on direct physical contact is the most efficient mode of heat transfer. By creating holes, at least a portion of the physical contact on the cantilever beam 220 is severed and replaced with air. This directly cuts off part of the heat conduction, and because air has a very low thermal conductivity, it provides some insulation. However, besides heat conduction, there is another secondary mode of heat transfer: heat convection. Heat convection is the movement of heat by flowing substances. As a flowing substance, air generates heat convection, and the heat loss caused by heat convection is also significant. Studies have shown that, at least in the design structure of the cantilever beam 220 sensor involved in this invention, heat loss due to heat conduction accounts for approximately 60%, and heat loss due to heat convection accounts for approximately 30%. To reduce heat loss in the central region 210 used for heating the gas-sensitive material, the heat transfer method of thermal convection cannot be ignored.

[0046] Therefore, this solution provides a preferred real-time example. In this embodiment, a roughened deposition structure is provided within the opening of the cantilever beam 220. The deposition structure realizes several heat-insulating chamber structures, each containing air capable of filling the chamber. Furthermore, each heat-insulating chamber does not necessarily need to be isolated from each other; generally, there can be some connectivity between the various heat-insulating chambers. The internal space dimensions of the heat-insulating chambers are controlled to be close to or below the mean free path of air, so that the air in the heat-insulating chamber is in a relatively microscopic, low-flow-activity state due to the Krusen effect. Based on the above, the Krusen effect describes that the flow of air in a microscopic environment is not equivalent to the flow in a macroscopic environment. Specifically, air molecules have a mean free path. When the space in which these air molecules exist is too small, such that it is less than or equal to the mean free path, the flow properties of the air decrease. Correspondingly, the convective heat conduction formed is reduced, thereby relatively reducing the amount of heat diffused outward from the central region 210 by thermal conduction. Preferably, the rough structure deposited inside the holes of the cantilever beam 220 can also be a gas-sensitive material. From a process perspective, depositing the gas-sensitive material into the central region 210 and depositing it onto the cantilever beam 220 can be performed in the same process step without adding any additional steps, thus maintaining consistent process costs. In terms of detection performance, the gas-sensitive material placed inside the holes of the cantilever beam 220 can also assist in gas detection to some extent, as this area still fully or partially contacts the heating and detection electrodes, enabling it to participate in some detection work. In terms of energy consumption, the gas-sensitive material formed inside the holes of the cantilever beam 220... The resulting roughened distribution, in other words, creates numerous porous and uniform or non-uniform chambers. These chambers, with volumes or sizes in the micrometer or even nanometer range, experience reduced airflow due to the Krusen effect, thus decreasing thermal convection. Therefore, in addition to introducing air with very low thermal conductivity through opening cavities (i.e., perforations) to prevent direct heat conduction, this invention also uses the deposition of roughened gas-sensitive materials within the perforations to form multiple chambers with inner diameters less than or equal to the air's mean free path, effectively trapping air molecules and reducing their flow properties. This further reduces heat dissipation through thermal conduction. Compared to simply preventing heat conduction, this solution also considers thermal convection, another major mode of heat dissipation, without significantly altering the process, and mitigates its impact, achieving a better synergistic effect and further improving the sensor's detection performance and energy efficiency.

[0047] The aforementioned roughened deposition structure can be achieved as follows: multiple cavities or protrusions are formed in the pore structure of the cantilever beam 220 (mainly in the AAO pore structure that makes up the cantilever beam 220) by etching or impact grinding, and then gas-sensitive material is deposited into the pores by deposition. After deposition, a layer of gas-sensitive material that is spaced apart and not tightly stacked can be formed on the inner wall of the pores, and there is a spatial cavity between a single gas-sensitive material particle and another particle.

[0048] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; terms such as "preferredly," "according to a preferred embodiment," or "optionally" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept.

Claims

1. A high-sensitivity microstructure gas sensor based on a three-cantilever structure. The system includes a central region (210) provided with a gas-sensitive material, the central region (210) being connected to a surrounding base layer (200) by three cantilever beams (220). Apart from being connected by the cantilever beams (220), the central region (210) does not contact the surrounding base layer (200). Its characteristic is that... The cantilever beam (220) is constructed as a porous structure, having a first end connected to the central region (210) and a second end connected to the base layer (200). The cantilever beam (220) is configured such that the aperture and spacing of the holes gradually change from the first end to the second end. The hole structure on the cantilever beam (220) is arranged such that the hole diameter gradually increases from the first end to the second end, wherein the first end and / or the portion near the first end is configured with relatively small holes and relatively densely arranged, and the second end and / or the portion near the second end is configured with relatively large holes and relatively dispersedly arranged.

2. The gas sensor according to claim 1, characterized in that, When the aperture of the cantilever beam (220) is set with a gradient change at various points, the transverse width of the cantilever beam (220) gradually increases from the first end to the second end.

3. The gas sensor according to claim 1, characterized by The substrate layer (200) is provided with a heating electrode by evaporation or sputtering, and the heat source coverage area of ​​the heating electrode is the area of ​​the central region (210).

4. The gas sensor according to claim 1, characterized by A detection electrode for detecting changes in the electrical parameters of the catalyst layer (100) is superimposed on the catalyst layer (100) disposed on the surface of the substrate layer (200), and the detection coverage area of ​​the detection electrode is the area of ​​the central region (210).

5. The gas sensor according to claim 1, characterized by When the filling member is filled into the partition space, it establishes a physical connection with all contact surfaces in the partition space, so that the compressive / tensile / bending forces generated on the cantilever beam (220) along its axial and / or radial directions can be dispersed by the deformation of the filling member itself.

6. The gas sensor according to claim 1, characterized by The substrate layer (200) is made of porous ceramic material.

7. The gas sensor according to claim 4, characterized by The catalyst layer (100) is composed of a catalyst material that can react with a specific gas and a catalyst material that can catalyze the reaction, wherein the catalyst material is a noble metal catalyst material.

8. The gas sensor according to claim 7, characterized by The noble metal catalytic material is doped onto the catalyst material.

9. The gas sensor according to claim 7, characterized in that, The noble metal catalyst material is obtained by drop-coating a pretreated H[PtCl] aqueous solution onto the sensing area and then heating it.

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