TWI705245B - Gas sensor - Google Patents

Abstract

The present invention is a gas sensor, including a substrate, an interdigital electrode, and a sensing film. The interdigital electrode has a bottom layer on the substrate, a first electrode on the bottom layer, and a second electrode On the bottom layer, the first electrode has a first body, and a plurality of first extensions extend from the first body, the second electrode has a second body, and a plurality of second extensions extend from the second body. The main body extends, and the first extensions and the second extensions are arranged alternately, so that the top surface of the interdigital electrode forms a receiving portion with a lower center than the surroundings, and the sensing film is located on the receiving portion Middle and attached to the first electrode and the second electrode. Thereby, the gas sensor has good detection sensitivity for gases such as acetone, high manufacturing yield, and lower manufacturing cost.

Description

Gas sensor

The present invention relates to a sensor, in particular to a gas sensor.

Studies in recent years have pointed out that the acetone concentration in the exhaled air of the human body has a highly linear relationship with the level of blood glucose, and the concentration of acetone exhaled by diabetic patients is also higher than that of healthy humans, so that non-invasive methods can be used. The gas sensing method replaces the traditional invasive test method of blood glucose meter that needs to tie hands to take blood drops to the blood glucose test strips. In addition to reducing the discomfort of the patient's hands, avoiding the problem that the wound is not easy to heal, it can also achieve rapid monitoring of blood glucose levels. High and low purpose.

However, gas sensors on the market today are usually used to detect the total volatile organic compounds (Volatile Organic Compounds, VOCs) and other gases that are harmful to the human body. Although there are alcohol sensors that can detect alcohol exhaled by the human body. Concentration, but there is no related development for low-concentration (500 ppb-2000 ppb) acetone gas sensors, and the acetone gas sensors that are still in the research stage have not been widely used. Therefore, how to make a non-invasive gas sensor have good detection sensitivity for acetone gas while reducing its manufacturing cost has become a common goal pursued by those skilled in the art.

One objective of the present invention is to provide a gas sensor that has good detection sensitivity for acetone gas, and can improve the process yield and reduce the manufacturing cost.

In order to achieve the above object, the gas sensor of the present invention includes a substrate, an interdigital electrode, and a sensing film. The interdigital electrode has a bottom layer disposed on the substrate, a first electrode disposed on the bottom layer, and a The second electrode is provided on the bottom layer. The first electrode has a first body and a plurality of first extensions extending from the first body. The second electrode has a second body and a plurality of second extensions. The second body extends, and the first extensions and the second extensions are arranged alternately, so that the top surface of the interdigital electrode forms a receiving portion with a lower center than the surroundings, and the sensing film is located on the The supporting part is attached to the first electrode and the second electrode. In this way, the gas sensor has good detection sensitivity for gases such as acetone, and can improve the process yield and reduce the manufacturing cost.

In the following, the technical content and features of the present invention will be described in detail with a preferred embodiment and drawings. As shown in Figures 1 to 3, a gas sensor 1 provided by a preferred embodiment of the present invention includes a The substrate 10, a finger electrode 20 are provided on the substrate 10, a sensing film 30 is attached to the finger electrode 20, four heating elements 40 are provided between the substrate 10 and the finger electrode 20, a temperature sensor The element 50 is disposed between the substrate 10 and the interdigital electrode 20 without contacting the heating elements 40, and a signal amplifying circuit (not shown) is electrically connected to the interdigital electrode 20.

The top surface 11 of the substrate 10 has two grooves 12 located below the heating element 40.

The interdigitated electrode 20 has a bottom layer 21 disposed on the top surface 11 of the substrate 10, a first electrode 22 disposed on the top surface of the bottom layer 21, and a second electrode 25 disposed on the top surface of the bottom layer 21. The first and second electrodes 22, 25 are electrically connected to the signal amplifying circuit. As shown in Figure 2, the first electrode 22 has a first body 23 that extends substantially along the left and right directions, and a plurality of first extensions 24 extend from the The first body 23 extends in the front-rear direction, and the thickness of each end of each first extension 24 away from the first body 23 is less than that of the first body 23. The second electrode 25 has a second body 26 substantially along the Extending in the left-right direction, and a plurality of second extensions 27 extend from the second main body 26 in the front-rear direction, each of the second extensions 27 has an end away from the second main body 26, and its thickness is less than the thickness of the second main body 26 , And the first extension portions 24 and the second extension portions 27 are parallel to each other and arranged in a staggered arrangement, so that the top surface of the interdigital electrode 20 forms a receiving portion 28 with a lower center than the periphery. The outer contour of the electrode 20 is approximately circular, and the supporting portion 28 is disk-shaped. Since the interdigital electrode 20 is made by micro-electromechanical technology, the first and second electrodes 22, 25 are formed in a way of layering on top of each other. The number of layers in the drawing is only for illustration and is not limited in practice. Since there is an insulating layer (not shown) between the bottom layer 21 and the first and second electrodes 22, 25, the bottom layer 21 will not be connected to the first and second electrodes 22, 25.

It should be noted that the bottom layer 21 is used as an etching stop layer to prevent the etching liquid from corroding other elements, such as the heating element 40 and the temperature sensing element 50 during the manufacturing process.

The sensing film 30 is located in the supporting portion 28 and attached to the first electrode 22 and the second electrode 25 with its bottom surface. The sensing film 30 contains metal oxide doped with carbon nano particles, The metal oxide can be WO ₃ , SnO ₂ , ZnO, Co ₃ O ₄ , TiO ₂ , NiO, In ₂ O ₃ or ZrO _2, etc. The carbon nanoparticle can be a single-wall carbon nanotube, a multi-wall Carbon nanotubes or graphene. Thereby, the sensing film 30, the first and second electrodes 22, 25 and the signal amplifying circuit can form a loop.

It should be noted that, because the liquid metal oxide with considerable viscosity is dropped on the interdigital electrode 20 during the manufacturing process, and then the sensing film 30 is formed by curing, the sensing film 30 will respond accordingly. The shape of the receiving portion 28 of the interdigital electrode 20 makes the central area thicker than the surrounding area. Since the thickness of the sensing film 30 in the center is about 1 mm, it is called a film.

The heating elements 40 are made of thermal resistance material and are arranged between the top surface 11 of the substrate 10 and the bottom layer 21 of the interdigital electrode 20, and are in the shape of a long and narrow sheet. The principle of thermal effect generates heat, and the sensing film 30 can be heated through the interdigital electrode 20. In addition, since most of the heating elements 40 are located above the grooves 12, almost only two ends are connected to the substrate 10. The air-based heat transfer efficiency is poorer than that of the substrate 10, and the arrangement of the grooves 12 reduces the connection area between the substrate 10 and each heating element 40, which can effectively reduce the heat loss through the substrate 10 Therefore, the heating element 40 can make the sensing film 30 reach the required operating temperature as long as the input of relatively low electrical energy is required.

The temperature sensing element 50 is approximately elongated and located in the center of the top surface 11 of the substrate 10. The temperature sensing element 50 is made of a thermal resistance material, because the thermal resistance material has different characteristics at different temperatures. Therefore, the gas sensor 1 can know the current temperature by the resistance value of the temperature sensing element 50. In other embodiments, the shape and position of the temperature sensing element 50 may have other changes.

In actual operation, a current is applied to the heating element 40 to make the heating element 40 heat the sensing film 30. At the same time, the current temperature is determined by the resistance change of the temperature sensing element 50. When the gas When the sensor 1 is heated to the working temperature, the sensing film 30 can produce a chemical reaction to change the resistance when it contacts the acetone gas. The change in resistance can be output through the interdigital electrode 20 and converted into a signal by the signal amplifier circuit. The voltage signal is used by an external system (not shown) to determine the corresponding blood glucose level.

With the above structure, the gas sensor has good detection sensitivity for low-concentration acetone gas, and in the manufacturing process, the shallow disc-shaped structure of the receiving portion 28 of the interdigital electrode 20 provides the sensing film 30 The limiting effect during coating enables the metal oxide to be automatically positioned in the supporting portion 28 due to gravity during dripping, which can improve the error tolerance rate of the processing process, effectively reduce the production failure rate, and thereby reduce the manufacturing Cost to achieve the purpose of the invention.

It should be noted that the gas sensor 1 of the present invention is manufactured using MEMS technology.

It should be noted that, in addition to sensing low-concentration acetone, the gas sensor 1 can also be used to sense oxygen by adjusting the composition of the sensing film 30 and the operating temperature of the gas sensor 1. , Carbon monoxide, carbon dioxide, volatile organic compounds (Volatile Organmic Compounds, VOCs) and other gases.

It should be noted that in other embodiments, the shape and number of the groove 12 and the heating element 40 may have other changes. For example, the groove 12 may be omitted. The shape of the outer periphery of the interdigital electrode 20 is not the focus of this case, but may have other changes, such as a square shape.

The foregoing is only an illustration of the embodiment of this creation, and cannot be used to limit the scope of the patent for this creation. For example, any simple modifications or changes made without going beyond the spirit of this creation, such as: the first extension 24 located on the farthest side of the first electrode 22 The thickness is the same as the thickness of the first body 23, or the second extension 27 at the side of the second electrode 25 has the same thickness as the second body 26, as long as the four circumferences of the interdigital electrode 20 are higher than the center. That is, as long as the top surface of the interdigital electrode 20 forms a supporting portion 28 with a lower center than the surroundings; or, the heating element 40 and the temperature sensing element 50 are made of other materials, and both should be applied for this creation Covered by the scope of the patent.

1: Gas sensor 10: substrate 11 top surface 12: Groove 20: Finger electrode 21: bottom layer 22: first electrode 23: The first subject 24: first extension 25: second electrode 26: The second subject 27: second extension 28: Housing Department 30: Sensing film 40: heating element 50: temperature sensing element

Figure 1 is a perspective view of a gas sensor according to a preferred embodiment of the present invention; Figure 2 is an exploded view of a gas sensor according to a preferred embodiment of the present invention; Figure 3 is a cross-sectional view of Figure 1 along the direction 3-3.

1: Gas sensor

10: substrate

20: Finger electrode

30: Sensing film

40: heating element

Claims (10)

A gas sensor, including: A substrate; An interdigitated electrode has a bottom layer on the substrate, a first electrode on the bottom layer, and a second electrode on the bottom layer. The first electrode has a first body, and a plurality of first extensions are formed by the The first body extends, the second electrode has a second body, and a plurality of second extensions extend from the second body. The first extensions and the second extensions are arranged alternately so that the The top surface of the interdigital electrode forms a receiving part with a lower center than the surroundings; and A sensing film is located in the supporting part and attached to the first electrode and the second electrode. The gas sensor according to claim 1, further comprising at least one heating element disposed between the substrate and the interdigital electrode. The gas sensor according to claim 2, wherein the top surface of the substrate is provided with at least one groove located below the heating element, so as to reduce the connection area between the substrate and the heating element. The gas sensor according to claim 2 or 3, further comprising a temperature sensing element arranged between the substrate and the interdigital electrode, and the temperature sensing element is not in contact with the heating element. The gas sensor according to claim 1, wherein the sensing film comprises metal oxide doped with carbon nano particles. The gas sensor according to claim 5, wherein the metal oxide is WO ₃ , SnO ₂ , ZnO, Co ₃ O ₄ , TiO ₂ , NiO, In ₂ O ₃ or ZrO ₂ . The gas sensor according to claim 5, wherein the carbon nanoparticle is a single-walled carbon nanotube, a multi-walled carbon nanotube, or graphene. The gas sensor according to claim 1, wherein the thickness of each end of each of the first extensions away from the first body is less than the thickness of the first body, and the end of each of the second extensions away from the second body The thickness is smaller than the thickness of the second body. The gas sensor according to claim 1, wherein the supporting portion is in the shape of a disc. The gas sensor according to claim 1, wherein the central area of the sensing film is thicker than the surrounding area.

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