A high-sensitivity microstructure gas sensor

Abstract

A high-sensitivity microstructure gas sensor includes a catalyst layer for reacting with a specific gas to change its own electrical property, has a substrate layer capable of serving as a catalyst layer loading area, and has a reaction area formed by the area of the catalyst layer provided on the substrate layer. A part of the substrate layer around the reaction area is excluded to form a vacant area. The reaction area is connected to the surrounding substrate layer through a narrow bridge formed by two remaining substrate layers still connected to the reaction area. A spacer section is provided at any position on the narrow bridge, which cuts across the width of the narrow bridge and extends along the axis of the narrow bridge without cutting off the narrow bridge. A filler composed of a second material different from the material constituting the narrow bridge is provided in the spacer section. The second thermal conductivity coefficient of the second material is configured to be smaller than the first thermal conductivity coefficient of the material constituting the narrow bridge.

Description

Technical Field

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

[0002] CN205139071U discloses a resistive gas sensor with a six-layer structure supported by two cantilever beams. The six layers, from bottom to top, are: a silicon substrate frame, a heating film layer, a heating layer, an isolation layer, an electrode layer, and a sensitive film layer. The sensitive film layer comprises two or more sensitive films, with the specific surface area gradually decreasing and the pore size gradually increasing from bottom to top. Compared with existing technologies, its two-cantilever beam structure allows for easier adjustment and control of the operating temperature to improve sensor performance; furthermore, the use of two or more sensitive film layers enhances the sensitivity and selectivity of the gas sensor.

[0003] CN205449863U discloses a resistive gas sensor with a four-support cantilever, four-layer structure. The four layers, from bottom to top, are: a silicon substrate frame, a heating film layer, a heating electrode layer, and a sensitive film layer. Each sensitive film layer comprises two or more layers, electrically connected layer by layer, with the specific surface area gradually decreasing and the pore size gradually increasing from bottom to top. Compared to existing technologies, its four-support cantilever structure allows for easier adjustment and control of the operating temperature to improve sensor performance; furthermore, the use of two or more sensitive film layers enhances the sensitivity and selectivity of the gas sensor.

[0004] Existing technologies employ cantilever beam structures to prevent significant heat loss through heat transfer from the surrounding structure. Based on general theory, the smaller the volume of the cantilever beam, the less heat loss occurs. However, at the microstructural scale of gas sensors, such tiny dimensions introduce structural strength issues. In particular, the stability of the cantilever beam structure is easily affected by impact forces and the thermal expansion and contraction of its connected components. Furthermore, uneven temperature distribution along the axial direction of the cantilever beam can lead to breakage due to large temperature differences.

[0005] 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.

[0006] 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

[0007] The operating temperature of a gas sensor directly affects its performance. Existing technologies typically employ a cantilever beam structure to provide the high-temperature environment required for sensor operation, thereby achieving temperature uniformity. For example, patent document CN104062342A discloses a gas detection sensor device, a method for operating the gas detection sensor device, and a method for manufacturing the gas detection sensor device. The gas detection sensor device includes a detection area and a readout area electrically and mechanically connected to the detection area via a connecting tab. The readout area, detection area, and connecting tab are formed from a substrate, and the detection area and connecting tab are formed through a recess in the substrate. This technical solution places the recess in the center of the substrate and sets it as a through-hole that can pass through the substrate, forming a free space with a size larger than the detection area. This creates an air gap between the detection area and the readout area. By bridging this air gap, the sensor device fulfills its function as a support structure for the detection area and simultaneously couples the detection area with the readout area. However, the connecting piece structure in this technical solution is subject to thermal expansion and contraction deformation due to temperature, which makes it prone to local cracks or fractures when subjected to external impact and / or thermal aging, ultimately leading to the failure of the gas sensor function.

[0008] To address the shortcomings of existing technologies, this invention provides a high-sensitivity microstructured gas sensor, comprising a catalyst layer for reacting with a specific gas to change its electrical parameters, a substrate layer serving as a load region for the catalyst layer, a reaction zone defined by the area of ​​the catalyst layer disposed on the substrate layer, and a vacant region formed by subtracting a portion of the substrate layer surrounding the reaction zone. The reaction zone is connected to the surrounding substrate layers by a narrow bridge formed by two remaining substrate layers to which it remains connected. An interval segment, extending axially along the narrow bridge without severing it, is disposed at any position on the narrow bridge. A filler composed of a second material different from the material constituting the narrow bridge is disposed within the interval segment, wherein the second thermal conductivity of the second material is configured to be lower than the first thermal conductivity of the material constituting the narrow bridge. Compared to the prior art, this invention uses the area of ​​the catalyst layer disposed on the substrate layer as the reaction zone, which is equivalent to placing the reaction zone on the surface of the substrate. Based on these distinguishing technical features, the technical problem to be solved by this invention is how to provide a suitable operating temperature for the gas sensor's detection area and improve the detection sensitivity of the detection area. Specifically, the aforementioned prior art embeds the detection area within a hollow region of the substrate material and detects the temperature of the sensitive area using the resistance of a heating element, the impedance of an ion conductor, or an additional integrated temperature measuring element. The etching process in its manufacturing method creates pits that provide sufficient volume for the empty spaces in the detection area. Miniaturization of the detection area allows for rapid and short-term heating, and the air gap between the detection and readout areas creates an atmosphere conducive to maintaining the corresponding operating temperature. However, in this technical solution, the target gas needs to enter the detection area embedded within the substrate and be detected only when the temperature reaches the corresponding operating temperature, resulting in relatively low overall detection sensitivity. In contrast, this invention forms a reaction zone by placing a catalyst layer on the substrate layer. This reaction zone is exposed to the substrate and can fully contact the target gas in the environment, thereby improving the detection sensitivity of the target gas.

[0009] Furthermore, compared to the prior art, the reaction zone and the surrounding substrate layer in this invention are connected by a narrow bridge. Each narrow bridge has a spacer segment, within which a filler material different from that constituting the narrow bridge is disposed. The second thermal conductivity of the filler material is lower than the first thermal conductivity of the material constituting the narrow bridge. Based on these distinguishing technical features, the technical problem this invention aims to solve is how to improve the structural strength of the gas sensor at different operating temperatures while reducing the overall power consumption of the sensor. Specifically, to maintain the structural strength of the connection between the reaction zone and the substrate, and to improve the efficiency of heating the reaction zone through heat transfer, the conventional connection structure between the reaction zone and the substrate in the prior art typically has the same structural width or thickness as the substrate or reaction zone. A larger structural surface area results in greater heat loss and a reduced ability to maintain heat in the core monitoring area, thus increasing the overall power consumption of the gas sensor. This invention, by setting a narrow bridge structure, can concentrate the generated heat in the core detection space of the reaction zone. This structural design eliminates most of the substrate layer that can directly transfer heat to the heat source, retaining only a narrow connecting bridge structure that is narrower than the reaction zone. This avoids a large amount of heat being lost through the substrate layer.

[0010] Furthermore, the aforementioned narrow bridge structure presents a new technical problem: it reduces the connection strength between the reaction zone and the substrate, making the gas sensor's connection structure prone to localized cracks or breaks, leading to overall functional failure. Additionally, due to the concentration of heat in the reaction zone, the substrate layer, the catalyst layer, the heating electrode, and the detection electrode in contact with it all experience thermal expansion. This exerts horizontal compressive force on the narrow bridge. Simultaneously, temperature drops in certain areas over time generate tensile forces in the opposite direction to the compressive force, further challenging the strength of the narrow bridge. To address these technical challenges, this invention uses a filler to reinforce the lost connection strength in the narrow bridge. This filler helps to offset some of the stress when the narrow bridge is under stress, thereby improving the overall strength of the connection structure. Furthermore, since the second thermal conductivity of the filler material is lower than the first thermal conductivity of the material that makes up the narrow bridge, a "cliff-like" difference in heat transfer capacity is formed on both sides of the interval segment filled by the filler. Heat that cannot be transferred in time can form a heat shield space here, preventing heat loss from the narrow bridge and better concentrating heat in the reaction area, thereby further reducing the overall power consumption of the sensor.

[0011] A high-sensitivity microstructured gas sensor includes a substrate layer, a portion of which is left vacant to form a reaction zone that is only partially connected to the substrate layer by a narrow bridge. The reaction zone is characterized by a catalyst layer for sensing a specific gas, and the narrow bridge having inwardly recessed but not interrupted intervals. Each interval contains a filler material different from that of the narrow bridge, wherein the thermal conductivity of the filler is configured to be lower than that of the narrow bridge.

[0012] This sensor is a MEMS, or micro-electromechanical system, which is small in size, usually at the chip level, and has a high degree of integration.

[0013] Preferably, several interval segments are spaced apart on the narrow connecting bridge near the reaction zone, so that heat is distributed on the substrate layer in a manner that concentrates towards the reaction zone.

[0014] Preferably, several fillers are filled into several interval segments respectively, and the fillers and the inner side of the interval segments form mutual abutment, so that the fillers can buffer the deformation of the interval segments in the event of compression or stretching deformation.

[0015] The second material, which is physically connected to each contact surface of the interval segments, reinforces the connection strength lost by the circumferentially spaced interval segments on the narrow bridge. This allows the narrow bridge to resist stress in the radial direction from the filler, thus providing some resistance to the support strength and inherent strength of the bridge itself. Furthermore, because the second thermal conductivity of the second material is lower than the first thermal conductivity of the materials constituting the narrow bridge, a heat shield is formed on both sides of the filler-filled interval segments. Heat that diffuses outward from the reaction zone along the axial direction of the narrow bridge is blocked by the filler in the pathway, further preventing heat loss from the narrow bridge. This allows for better heat concentration in the reaction zone, further reducing the overall power consumption of the sensor and greatly benefiting the realization of low-power or even ultra-low-power sensing solutions.

[0016] Preferably, a spacer segment is provided on the portion of the narrow bridge near the reaction zone, which is transverse to the width of the narrow bridge and extends along the axial direction of the narrow bridge without cutting off the narrow bridge. The spacer segment is filled with a filler composed of a second material different from the material constituting the narrow bridge.

[0017] By placing the filler near the reaction zone, some of the heat dissipated by the narrow bridge is blocked from leaving the reaction zone, allowing most of the heat to remain within the reaction zone. This effectively improves the heating efficiency of the heating electrode, reduces ineffective energy consumption, and further lowers the overall power consumption of the sensor. Furthermore, the filler near the reaction zone prevents heat spread along the narrow bridge, reducing the temperature gradient along the bridge's axial direction to a negligible level. This reduces or eliminates the difference in thermal stress intensity between different parts of the narrow bridge caused by temperature differences, significantly preventing localized cracks or fractures due to external impacts and / or thermal aging. Additionally, research shows that the flexural strength of the narrow bridge gradually decreases from the center to the ends. Placing the filler near the edge of the narrow bridge near the reaction zone avoids the problem of reduced strength in the middle section caused by creating a gap in the middle.

[0018] Preferably, on the portion of the narrow bridge near the reaction zone, one or more interval segments are provided around the circumference of the narrow bridge, with the narrow bridge axis as the center. The interval segments are recessed towards the central axis of the narrow bridge but do not sever the central axis of the narrow bridge, so that the narrow bridge still maintains the integral physical connection of the central axis.

[0019] The circumferentially arranged filler can more thoroughly seal off some of the heat conducted by the narrow bridge, and can prevent heat from being conducted out of the reaction zone as much as possible. It also ensures a certain degree of uniformity in the heat distribution of the narrow bridge itself.

[0020] Preferably, a heating electrode is provided on the negative side of the substrate layer using a coating process. Preferably, the heat source of the heating electrode can cover the reaction zone.

[0021] 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 reaction zone.

[0022] Preferably, when the filler is filled into the spacer segment, it establishes a physical connection with all contact surfaces in the spacer segment, so that the compressive / tensile / bending forces generated in the narrow bridge along its axial and / or radial direction can be dispersed by the deformation of the filler itself.

[0023] The filler reinforces the flexural strength of the narrow bridge. Viewed axially, the narrow bridge is initially affected by the thermal expansion or contraction of the reaction zone. Normally, the narrow bridge would be subjected to compressive or tensile forces in its axial direction, which is detrimental to its strength. However, due to the introduction of the filler, its ductility and the stress release of the spacer section itself act as a buffer against these compressive or tensile forces. This reduces the impact of thermal expansion and contraction of the reaction zone on the compression or tension of the narrow bridge, significantly contributing to its strength and preventing breakage. Furthermore, the width of the narrow bridge can be further reduced to minimize heat loss channels, which is highly beneficial for heat preservation of the reaction zone. Furthermore, from a radial perspective, since the aforementioned filler blocks most of the heat transfer within the narrow bridge, the axial temperature gradient distribution difference along the narrow bridge will be further reduced. In fact, if the thermal conductivity of the selected filler is sufficiently low, the temperature distribution difference will be reduced to a negligible level. This ensures that the radial flexural strength of each part of the narrow bridge will not be differentiated due to temperature differences, eliminating any "weak points" in the narrow bridge. The overall strength of the narrow bridge is further enhanced, enabling it to more readily withstand the strong flexural effects of impacts. This ensures that the sensor can operate normally in environments with significant vibrations, thus expanding the applicability of the device.

[0024] Preferably, the substrate layer is composed of porous metal oxide, wherein a two-step anodizing process is used to obtain a single-pass and / or double-pass metal oxide as the substrate layer.

[0025] Preferably, the catalyst layer is composed of a catalyst material capable of reacting with a specific gas and a catalyst material capable of catalyzing the reaction.

[0026] Preferably, the catalytic material is attached to the catalyst material.

[0027] Preferably, the catalyst is obtained by drop-coating a pretreated aqueous solution of H2[PtCl6] onto the sensing area and then heating it.

[0028] Based on a different implementation method compared to the prior art, the technical problem to be solved by the present invention is how to improve the response sensitivity of gas sensors. In the prior art, the substrate structure is typically a planar plate structure, and the catalyst material can only be attached to the surface of the planar plate structure. In contrast, the substrate layer of the present invention is composed of porous metal oxides. Porous metal oxides have a large specific surface area, making them excellent catalyst support materials. Furthermore, their manufacturing process is simple and efficient, and the catalyst material can be well attached to the pores of the porous metal oxide, resulting in a high response. The narrow-bridge substrate of porous metal oxides fabricated using laser cutting can effectively reduce heat conduction in the active region, increase the thermal efficiency of the micro-heater, and thus reduce power consumption. The entire sensor manufacturing process is well compatible, enabling mass production and significantly improving manufacturing efficiency. On the other hand, the porous metal oxide substrate material used in the present invention has several regularly arranged channels. Therefore, when constructing the interval segments, some of the existing channel space can be utilized to construct the interval segments by connecting or not connecting them, and filler can be placed inside them. There is no need to go through additional process steps to form channel space for carrying the filler, thereby improving the manufacturing efficiency of the sensor.

[0029] Preferably, in the case of several adjacent reaction zones, a connecting member is provided, which is configured to connect the heat source center of one of at least two adjacent or non-adjacent reaction zones 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 reaction zones and the heat retreat edge of the other. The connecting member can be structured based on one or more of three heat transfer pathways, namely heat conduction, heat convection, and heat radiation, so as to enable it to realize one or more of the above three heat transfer pathways.

[0030] Preferably, the connecting member physically contacts or does not contact the reaction zone or the periphery of the reaction zone in a manner that facilitates heat transfer between the heat source center and the heat-pushing edge to which it is connected. Preferably, physical contact is used; more preferably, the connecting member connects the narrow bridges corresponding to the two reaction zones, and the connection area is preferably the portion between the reaction zone and the filler. When the connecting member does not form physical contact with the reaction zone or the periphery of the reaction zone, the heat transfer method is heat convection or heat radiation; when the connecting member forms physical contact with the reaction zone or the periphery of the reaction zone, preferably forming a connection, the heat transfer method is heat conduction, heat convection, or heat radiation, and the connecting member provides mutual support to the reaction zone or the periphery of the reaction zone (e.g., the aforementioned narrow bridge portion), which enables the reaction zone and / or the narrow bridge portion to have higher structural strength and is less susceptible to structural damage or breakage caused by the kinetic energy generated by accidental impacts. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the device structure provided by the present invention;

[0032] Figure 2 This is a schematic diagram of the structural dimensions of the present invention;

[0033] Figure 3 This is an enlarged schematic diagram of the narrow connecting bridge structure of the present invention;

[0034] In the diagram: 100, substrate layer; 110, narrow connecting bridge; 120, void area; 130, reaction zone; 140, spacer segment; 150, filler; 200, heating electrode layer; 300, catalyst layer. Detailed Implementation

[0035] Next, we will combine the appendix Figure 1-3 Further explanation is needed.

[0036] This invention provides a microstructured gas sensor. Due to its microstructure, its size is extremely small, typically allowing it to be fabricated at the chip level and integrated into other circuits or smart devices to provide gas sensing functionality. Because of its microstructure, the physical influences on its structure must be considered at the microscopic level. At the microstructure level, the gas sensor needs to achieve gas sensing within a certain range using small circuit components. The sensing principle applicable to this solution is: utilizing the coupling reaction between a sensing material heated to a specific temperature range and gas molecules, resulting in a specific change in electrical parameters to detect the gas. Based on this, the microstructured gas sensor can be composed of a heating electrode layer, a substrate layer, and a detection electrode layer. The heating electrode layer and the detection electrode layer sandwich the substrate layer. A catalyst layer is disposed on the substrate layer; the catalyst layer is either the sensing material or the sensing material is deposited on the catalyst layer. Furthermore, to ensure the structural strength of the gas sensor and its compatibility with other circuit components, the area of ​​the catalyst layer is smaller than the narrow bridge of the substrate layer. In other words, only a portion of the three-layer structure consisting of the heating electrode layer, the substrate layer, and the detection electrode layer is used for reacting with the gas. This region is called the reaction zone. There are gaps between the reaction zone and the surrounding area, allowing the reaction zone to be electronically and mechanically connected to the surrounding area only through narrow bridges. In this embodiment, there are two narrow bridges. Preferably, the narrow bridges are symmetrically arranged at the edges of the reaction zone. Preferably, the main structure of the narrow bridge is still the substrate layer. In other words, the main structure of the narrow bridge is obtained by hollowing out a portion of the original monolithic substrate layer. The substrate layer portion belonging to the reaction zone is also constructed using the aforementioned hollowing-out method. The hollowed-out portion is called the void region. The mechanical connection between the reaction zone and the surrounding area means that the reaction zone is physically held to other parts of the substrate layer through the narrow bridges. The electronic connection between the reaction zone and the surrounding area means that a portion of the heating electrode layer and a portion of the detection electrode layer in the reaction zone are connected to the remaining portions of the two layers in the surrounding area through conductors disposed on the narrow bridges. The conductors can be thin metal wires, electrical wires, etc. The heating electrode layer located in the reaction zone is the heating electrode wire, and the heating electrode layer located in the surrounding area is the positive and negative lead-in area of ​​the heating electrode. The detection electrode layer located in the reaction zone is the detection electrode wire, and the detection electrode layer located in the surrounding area is the positive and negative lead-in area of ​​the detection electrode.

[0037] Preferably, the gas sensor layer structure may further include a substrate, a support layer, and an insulating layer. The substrate is disposed at the bottom layer of the layer structure, and the support layer is disposed on the substrate to support the substrate layer, etc. The insulating layer is used to electrically isolate the detection electrode layer and the heating electrode layer.

[0038] The substrate layer is preferably a porous structure. The substrate layer can be made of a material. Preferably, a porous metal material can be selected to make the substrate layer. In this embodiment, the pore size on the substrate layer is small, reaching the micrometer or even nanometer range. The purpose of setting the substrate layer as a porous structure is to be able to load more catalyst layer material, thereby increasing the contact area between the catalyst layer material and gas molecules, thus increasing the detection area or improving detection efficiency or sensitivity. Preferably, a two-step anodizing process is used to prepare single-pass and double-pass porous metal oxide nanotubes. The catalyst layer can be selected according to the gas to be detected, for example, it can be semiconductor materials such as In2O3, SnO2, and Mn3O4. Furthermore, a catalytic material can also be set on the catalyst layer. The catalytic material is used to catalyze the reaction between the catalyst material and gas molecules, improving detection efficiency and sensitivity. The catalytic material can be some noble metal materials, oxide catalysts, or composite catalysts, etc. Preferably, the surface catalytic material is formed by drop-coating a pretreated H2[PtCl6] aqueous solution onto the sensing area and heating it. The catalyst layer and the catalytic material layer are combined to form the catalyst layer 300.

[0039] The detection electrode layer consists of a detection electrode and a standard electrode, which form an electrode pair in the circuit. The standard electrode is used to calibrate the detection results. 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.

[0040] The heating electrode layer includes at least heating electrode wires that convert electrical energy into heat energy. The heating electrode wires are shaped to fit the reaction zone, allowing for targeted heating of this specific area. This configuration helps concentrate heat at a single point, enabling the application of a relatively high current to this small portion of the heating electrode wires. This provides higher heating power to the planting area, facilitating rapid heating of the reaction zone to the high temperatures required for the sensing gas. The heating electrodes are fabricated using a coating process.

[0041] The present invention also provides a process for fabricating a narrow-bridge gas sensor, which includes the following steps.

[0042] S1 was used to prepare porous metal oxide substrates;

[0043] S2 prepares a catalyst layer 300 in a specific area on the front side;

[0044] S3 deposition under surface heating metal;

[0045] S4 etching of multiple narrow bridge 110 structures;

[0046] Step S4 can be replaced by laser engraving of a porous metal oxide substrate to form a structure of two narrow bridges 110.

[0047] Another embodiment also provides an alternative preparation process, as follows.

[0048] S1 is used to prepare silicon substrates;

[0049] S2 has a silicon nitride / silicon oxide support layer disposed on a silicon substrate;

[0050] S3 has heating electrodes deposited on the support layer using a coating process.

[0051] S4 has a silicon oxide insulating layer disposed on the heating electrode;

[0052] S5 has a down-detection electrode on the isolation layer;

[0053] S6 has a substrate layer 100 disposed on the down-detection electrode;

[0054] S7 prepares a catalyst layer 300 on a substrate layer 100;

[0055] S8 has an up-detection electrode superimposed on the catalyst layer 300;

[0056] Preferably, to prevent a large amount of heat from being dissipated by the substrate 100 directly contacting the substrate layer 100 when the heating electrode utilizes the heat transfer from the heated substrate layer 100 to heat the catalyst layer 300 located on the surface of the substrate layer 100, this device is provided with a structure of two narrow bridges 110. Specifically, an empty area is cut out of the formed substrate layer 100 by etching, and a platform structure physically connected to the substrate layers 100 surrounding the empty area is provided in the middle of the empty area. According to this solution, the platform structure can have two narrow bridges 110, which are respectively connected from the reaction zone 130 of the platform structure and respectively connected to the substrate layers 100 surrounding the empty area. The platform structure is constructed in the same way as the substrate layer 100. Since the above-mentioned etching method is used, the platform structure is actually integral with the substrate layer 100 before etching. The two narrow bridges 110 are configured to not cover the entire empty area. Preferably, to minimize heat loss, the width of the narrow bridges 110 is smaller than the width of the reaction zone 130. According to one example, the width of the reaction zone 130 is configured to be 360 ​​μm, the side of which is also connected to the narrow bridges 110. On the other hand, the width of the narrow bridges 110 is configured to be 160 μm. In this structure, the narrow bridges 110 are smaller than the reaction zone 130 in width. This structure, with a wide reaction zone 130 and relatively narrow narrow bridges 110, helps to minimize the heat loss from the heating electrode to the reaction zone 130 through heat conduction via the narrow bridges 110. It allows heat to be retained primarily in the portion of the reaction zone 130 containing the gas-sensitive material. This significantly contributes to reducing the power consumption of the gas detector and achieving low-power or even ultra-low-power gas detection functionality.

[0057] In this embodiment, the reaction zone 130 is generally configured as a square platform with four roughly parallel sides. Two narrow bridges 110 are respectively connected to two symmetrical sides of the reaction zone 130, and preferably arranged such that their axial directions coincide with the horizontal or vertical bisectors of the reaction zone 130. Based on this, the vacant area is generally formed into two roughly symmetrical areas divided by the reaction zone 130 and the narrow bridges 110.

[0058] According to a preferred embodiment, this embodiment is a preferred embodiment based on considerations of the following technical problems. In order to solve the problem of how the heat generated under the hard requirements of using a gas sensor with low power consumption can be more concentrated in the core detection space of the reaction zone 130, a structure of narrow bridge 110 has emerged. This structure, by deducting most of the substrate layer 100 that can directly transfer heat with the heat source (i.e., the heating electrode), and retaining only the narrow bridge 110 structure which is narrower than the reaction zone 130, avoids a large amount of heat loss through the substrate layer 100. However, at the same time, it has a negative impact on the structural strength of the core detection space. As described above, gas sensors can be scaled down to the chip level, i.e., from micrometers to nanometers. At such a small scale, the physical strength of the narrow bridge 110 is greatly challenged. As the width of the narrow bridge 110 decreases, its flexural strength in the vertical direction also decreases. This means that both the weight of the reaction zone 130 itself and the additional impacts in the vertical direction pose a significant challenge to the resistance of the narrow bridge 110 to brittle fracture. On the other hand, due to the concentration of heat in the reaction zone 130, the substrate layer 100 contained in the reaction zone 130, the catalyst layer 300 it contacts, the heating electrode, and the detection electrode will all experience thermal expansion. This generates a compressive force on the narrow bridge 110 in the horizontal direction. At the same time, the temperature drop in certain parts at certain times will generate a tensile force on the narrow bridge 110 in the opposite direction to the compressive force. These stresses also pose a challenge to the strength of the narrow bridge 110. Regarding heat transfer, based on the theory of heat transfer, the direction of heat conduction on the narrow bridge 110 is roughly along the axial direction of the narrow bridge 110. Since the width of the narrow bridge 110 is relatively small compared to its length, heat diffuses rapidly in the width direction, resulting in a small temperature gradient difference that can be ignored in this discussion. However, in the axial direction of the narrow bridge 110, based on the thermodynamic theory of heat loss, the resulting temperature gradient is relatively significant. The different temperature distributions at different locations obviously also have a certain impact on the strength of various parts of the narrow bridge 110. For the material forming the substrate layer 100 (e.g., the porous metal oxide used in this embodiment), the higher the temperature, the weaker its structural strength. Therefore, the temperature gradient generated by heat transfer along the axial direction of the narrow bridge 110 also poses a significant challenge to the structural strength of the narrow bridge 110 itself. Regarding the porous metal oxide substrate 100 material used in this embodiment, it has several regularly arranged channels. Therefore, when constructing the spacer segment 140, some of the already formed channel space can be used to construct the spacer segment 140 in a way that allows them to be interconnected or not interconnected, and a filler 150 can be placed inside it. The channels themselves can be single-pass or double-pass based on the process, which does not have a significant impact on the formation of the spacer segment 140.

[0059] Based on the above-mentioned problems, according to this preferred embodiment, a spacer segment 140 is provided at any position on the narrow bridge 110, and a filler 150 composed of a second material different from the material constituting the narrow bridge 110 is provided within the spacer segment 140. Further, a spacer segment 140 is provided at any position on the narrow bridge 110, which transversely interrupts the width of the narrow bridge 110 and extends a certain distance along the axial direction of the narrow bridge 110 without severing the narrow bridge 110, and a filler 150 composed of a second material different from the material constituting the narrow bridge 110 is provided within the spacer segment 140. Even further, a spacer segment 140 is provided on the portion of the narrow bridge 110 near the reaction zone 130, which transversely interrupts the width of the narrow bridge 110 and extends a certain distance along the axial direction of the narrow bridge 110 without severing the narrow bridge 110, and a filler 150 composed of a second material different from the material constituting the narrow bridge 110 is provided within the spacer segment 140. Furthermore, on the portion of the narrow connecting bridge 110 near the reaction zone 130, one or more interval segments 140 are provided circumferentially around the axis of the narrow connecting bridge 110. The interval segments 140 are recessed towards the central axis of the narrow connecting bridge 110 without severing it, thus maintaining the integral physical connection of the central axis of the narrow connecting bridge 110. Furthermore, the degree to which each interval segment 140 is recessed towards the central axis of the narrow connecting bridge 110 is limited to a maximum limit. This maximum limit can be determined by engineers considering the relationship between the maximum stress the structure of the narrow connecting bridge 110 can withstand and the width of the retained connection portion when it is circumferentially reduced to retain only the integral connection portion near the central axis. The filler 150 made of the second material can be filled into the interval segments 140 in such a way that it fills all the interval segments 140, and preferably, the filler 150 establishes a connection relationship with all contact surfaces of the interval segments 140. The aforementioned connection can be achieved, for example, by depositing filler 150 into the spacer segment 140. The filler 150 has a second thermal conductivity coefficient, and the material constituting the narrow bridge 110 has a first thermal conductivity coefficient. According to this embodiment, the second thermal conductivity coefficient is configured to be less than the first thermal conductivity coefficient. The second material can be selected as a non-conductive material with low thermal conductivity, for example, a material with good insulation and low thermal conductivity.

[0060] The second material, which is physically connected to each contact surface of the interval segment 140, reinforces the connection strength of the narrow bridge 110 that is lost due to the interval segment 140 extending along its circumferential axis. This allows the narrow bridge 110 to resist stress in the radial direction from the filler 150, thus providing some resistance to the support strength of the narrow bridge 110 and the strength of the narrow bridge 110 itself. Furthermore, since the second thermal conductivity of the second material is lower than the first thermal conductivity of the materials constituting the narrow bridge 110, a heat shield is formed on both sides of the interval segment 140 filled with the filler 150. The heat that diffuses outward from the reaction zone 130 along the axial direction of the narrow bridge 110 is blocked by the filler 150 in the passage, further preventing heat loss from the narrow bridge 110. This allows for better heat concentration at the reaction zone 130, further reducing the overall power consumption of the sensor and greatly benefiting the realization of low-power or even ultra-low-power sensing solutions. On the other hand, the filler 150 reinforces the flexural strength of the narrow bridge 110. Observing from the axial direction of the narrow bridge 110, it is initially affected by the thermal expansion or contraction of the reaction zone 130. Originally, the narrow bridge 110 would be subjected to compressive or tensile forces in its axial direction, which is detrimental to the strength of the narrow bridge 110 itself. However, due to the introduction of the filler 150, and due to the extensibility of the filler 150 and the stress release of the interval segment 140 itself, the filler 150 forms a buffer against the aforementioned compressive or tensile forces. This reduces the impact of the thermal expansion and contraction of the reaction zone 130 on the compression or tension of the narrow bridge 110, which greatly helps to ensure the strength of the narrow bridge 110 and prevent it from breaking. Furthermore, based on this, the width of the narrow bridge 110 can be further reduced to further decrease the channels for heat loss, which is very beneficial for the insulation of the reaction zone 130. Furthermore, from a radial perspective of the narrow bridge 110, since the filler 150 blocks most of the heat transfer within the narrow bridge 110, the axial temperature gradient distribution difference along the narrow bridge 110 is further reduced. Even when the thermal conductivity of the filler 150 is sufficiently low, this temperature distribution difference is reduced to a negligible level. This ensures that the radial flexural strength of each part of the narrow bridge 110 is not differentiated due to temperature variations, eliminating any "weak points" in the narrow bridge 110. The overall strength of the narrow bridge 110 is further enhanced, allowing it to more readily withstand the strong flexural effects of impacts. This ensures the sensor functions normally in environments with high vibration, expanding the applicability of the device. Additionally, the above solution maintains the heat in the reaction zone 130 within the current area, further improving the sensor's thermal response speed. Since thermal response speed is related to the sensor's detection sensitivity, this solution makes the sensor more sensitive, resulting in improved detection response and feedback.

[0061] According to a preferred embodiment, this embodiment includes several adjacent sensor structures; in other words, it includes several adjacent reaction zones 130 and heating electrodes, catalyst layers 300, and detection electrodes disposed on the reaction zones 130. In this embodiment, based on the heat distribution circumferentially around a single reaction zone 130, 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 reaction zones 130 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 reaction zone 130. 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 range, away from the core heating range of the heating electrode. This temperature difference is detrimental to detection because it prevents the full utilization of the catalyst material in the catalyst layer 300 located above the central platform for gas detection. Furthermore, different temperature differences may also cause potential imbalances on the detection electrodes, resulting in detection fluctuations. Increasing the temperature of the heating electrode to raise the temperature of the thermally degraded 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 reaction zones 130 and the thermally degraded 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 reaction zones 130 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 involves using a structure that creates a fluid pathway, such as a tubular structure. Gas flows through the connecting member, and because the temperature at the heat source center is high, the gas near the heat source 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 based on a heat radiation-based pathway structure. In this structure, the connecting member may not need to be in physical contact with either the heat source center or the heat-reducing edge. The end near the heat source center can be configured to absorb more heat radiation, while the end near the heat-reducing edge can be configured to release more heat radiation. For example, different materials can be used at both ends to achieve heat radiation absorption and release. Ultimately, the heat radiation generated at the heat source center causes the connecting member to heat up, which in turn causes the heat transferred to the heat-reducing edge by the connecting member to heat up in the form of heat 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 heat radiation can be used to simultaneously achieve both heat transfer pathways.

[0062] This embodiment presents a dimensional design scheme for the narrow-bridge gas sensing device. The thickness of the substrate, made of porous metal oxide material, is set to 20 μm; the thickness of the heating electrode, made of Pt / Ti, is selected as 200 nm / 10 nm; the width of the heating electrode wire is selected as 40 μm; the wire spacing of the heating electrode is selected as 40 μm; the width of the detection electrode wire is selected as 40 μm; the wire spacing of the detection electrode is selected as 40 μm; and the pore size of the porous metal oxide is selected as 400 μm. The overall sensor size is set to 3000 μm * 3000 μm.

[0063] 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 microstructured gas sensor, comprising a substrate layer (100), wherein a portion of the substrate layer (100) is vacant to form a reaction region (130) thereon, which is partially connected to the substrate layer (100) only by narrow bridges (110), characterized in that, The reaction zone (130) is provided with a catalyst layer (300) for sensing a specific gas. The narrow bridge (110) is provided with an inwardly recessed but not cut-off interval segment (140). The interval segment (140) is provided with a filler (150) of a different material than the narrow bridge (110). The thermal conductivity of the filler (150) is configured to be less than that of the narrow bridge (110). Several fillers (150) are respectively filled into several spacer segments (140), and the fillers (150) and the inner side of the spacer segments (140) are in mutual contact, so that the fillers (150) can buffer the deformation of the spacer segments (140) in the event of compression or stretching deformation.

2. The gas sensor according to claim 1, characterized in that, Several interval segments (140) are spaced apart on the narrow bridge (110) near the reaction zone (130), such that heat is distributed on the substrate layer (100) in a manner that concentrates toward the reaction zone (130).

3. The gas sensor according to claim 1, characterized in that, The lower surface of the substrate layer (100) is provided with a heating electrode by a coating process, and the heat source coverage area of ​​the heating electrode is the area of ​​the reaction zone (130).

4. The gas sensor according to claim 1, characterized in that, A detection electrode for detecting changes in the electrical parameters of the catalyst layer (300) is superimposed on the catalyst layer (300) disposed on the surface of the substrate layer (100), and the detection coverage area of ​​the detection electrode is the area of ​​the reaction region (130).

5. The gas sensor according to claim 1, characterized in that, When the filler (150) is filled into the spacer segment (140), it establishes a physical connection with all contact surfaces in the spacer segment (140), so that the compressive or tensile forces generated on the narrow bridge (110) along its axial and / or radial directions can be dispersed by the deformation of the filler (150) itself.

6. The gas sensor according to claim 1, characterized in that, The substrate layer (100) is composed of porous metal oxide, wherein a two-step anodizing process is used to obtain a single-pass and / or double-pass porous metal oxide as the substrate layer (100).

7. The gas sensor according to claim 1, characterized in that, The catalyst layer (300) is composed of a catalyst material capable of reacting with a specific gas and a catalyst material capable of catalyzing the reaction.

8. The gas sensor according to claim 7, characterized in that, The catalytic material is attached to the catalyst material.

9. The gas sensor according to claim 7, characterized in that, The catalyst material is obtained by drop-coating a pretreated H2[PtCl6] aqueous solution onto the sensing area and then heating it.

Images