TW201830009A - Gas sensor and method of manufacturing the same - Google Patents

Abstract

A gas sensor including a substrate, an output layer, a sensing layer and a nanoporous polymer film is provided in the present invention. The output layer is disposed on the substrate. The sensing layer is disposed on the output layer. The nanoporous polymer film is disposed on the sensing layer.

Description

Gas sensor and method of manufacturing same

The present invention relates to a gas sensor and a method of manufacturing the same, and more particularly to a gas sensor having a nanoporous polymer film and a method of manufacturing the same.

Conventional gas sensors are in contact with the sensing layer by providing a material having micropores on the sensing layer such that gas molecules having a size smaller than the microchannels pass through the microchannels. Conversely, gas molecules larger than the micropores cannot pass through the microchannels, so they cannot contact the sensing layer.

However, it is known that the material having micropores is anodized aluminum. Since the anodized aluminum is a metal oxide material, the degree of adhesion to the sensing layer is insufficient, which is liable to cause a problem of insufficient durability of the gas sensor.

The invention provides a gas sensor and a manufacturing method thereof, which have excellent durability and functional performance.

The invention provides a gas sensor comprising: a substrate, an output layer, a sensing layer and a nanoporous polymer film. The output layer is disposed on the substrate. The sensing layer is disposed on the output layer. The nanoporous polymer film is disposed on the sensing layer.

In an embodiment of the invention, the pores of the nanoporous polymer membrane have a diameter of from 0.2 nm to 20 nm.

In an embodiment of the invention, the nanoporous polymer film has a thickness of from 0.05 micrometers to 150 micrometers.

In an embodiment of the invention, the material of the nanoporous polymer film comprises a perfluorosulfonic acid polymer, nano cellulose or a combination thereof.

In an embodiment of the invention, the nanoporous polymer membrane described above comprises an ionic structure.

In an embodiment of the invention, the output layer comprises an electrode.

In an embodiment of the invention, the surface of the substrate comprises a plane, a rough surface, a curved surface or a combination thereof.

The present invention also provides a method of fabricating a gas sensor, comprising: forming an output layer on a substrate; forming a sensing layer on the output layer; and forming a nanoporous polymer film on the sensing layer.

In an embodiment of the invention, the above-described method of forming the output layer, forming the sensing layer, and forming the nanoporous polymer film comprises three-dimensional printing.

In an embodiment of the invention, the method of forming the nanoporous polymer film described above comprises performing a solution process.

Based on the above, the nanoporous polymer membrane of the present invention has minute pores selectively allowing smaller molecules to pass and blocking larger molecules. In addition, the nanoporous polymer membrane is located on the sensing layer of the gas sensor to provide better protection of the sensing layer. Therefore, the gas sensor of the present invention has excellent durability and functional performance.

The above described features and advantages of the invention will be apparent from the following description.

1 is a schematic view of a gas sensor according to an embodiment of the present invention. Referring to FIG. 1 , the gas sensor 100 includes a substrate 102 and an output layer 104 , a sensing layer 106 , and a nanoporous polymer film 108 disposed from the bottom. After passing through the nanoporous polymer film 108, the gas molecules interact with the underlying sensing layer 106 to change the resistance of the sensing layer 106. The output layer 104 receives the signal generated by the physical characteristics (such as resistance, capacitance or impedance) of the sensing layer 106, and according to the detected signal, the resistance change of the sensing layer 106 can be known, and then the detected signal is detected. The type, composition or content of the measured gas molecules.

The surface of the substrate 102 can be planar, non-planar, or a combination thereof. The plane can be a smooth surface or a rough surface. Non-planar surfaces can be convex surfaces, concave surfaces, biconcave surfaces, or biconvex surfaces. In embodiments where the substrate 102 is a non-planar surface, the gas sensor 100 can be placed in a non-planar location or body, thus having a broader range of applications. The substrate 102 can be a flexible material or a rigid material. The material of the substrate 102 is, for example, glass, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI). , PolyVinyl Chloride (PVC), Polypropylene (PP), cycloolefin polymer (COP), polyethylene (PE) or a combination thereof.

The output layer 104 is disposed on the substrate 102. The output layer 104 can measure the physical characteristics (eg, resistance, capacitance, or impedance) of the sensing layer 106. In some embodiments, the output layer 104 can be an electrode, a switch (eg, a thin film transistor, a bipolar transistor (BJT), a diode), or a combination thereof. In embodiments where the output layer 104 can be an electrode, the electrodes can receive signals for transmission to the detection device.

The present invention does not particularly limit the constituent members and configurations of the output layer 104, as long as the output layer 104 can measure the physical properties (eg, resistance, capacitance, or impedance) of the sensing layer 106, and is encompassed within the scope of the present invention. . In some embodiments, the output layer 104 has a gap. 2 is a schematic cross-sectional view of a gas sensor in accordance with an embodiment of the present invention. Referring to FIG. 2 , the output layer 104 has a gap, so that the sensing layer 106 can be disposed in the gap of the output layer 104 . Thereby, a higher contact area between the output layer 104 and the sensing layer 106 can be achieved, so that the signal intensity between the output layer 104 and the sensing layer 106 can be increased to increase the sensitivity of the gas sensor. In the present embodiment, the output layer 104 is, for example, a fork electrode. In embodiments where the output layer 104 is an interdigitated electrode, the interdigitated electrode has a body portion and a plurality of extensions, wherein the body portion extends in one direction and the extension portion extends in the other direction. The two ends can be selected on the interdigitated electrode, and the physical properties (such as resistance, capacitance, or capacitance between the two ends of the interdigitated electrode are measured by the distance between the two ends. The impedance is changed to know the amount of change in the resistance of the sensing layer 106, and the type, composition or content of the gas to be tested is known. In FIG. 2, the sensing layer 106 fills the gap of the output layer 104, but the invention is not limited thereto. In other embodiments, the sensing layer 106 may also fill only a portion of the gap of the output layer 104 without filling the gap to reduce the manufacturing process difficulty of the gas sensor of the present invention. Output layer 104 includes a conductor material. The conductor material may be a metal or a metal alloy. Output layer 104 can also be a Group IV element or other type of material. The material of the output layer 104 is, for example, carbon powder, carbon nanotubes, graphene, reduced graphene oxide, gold, platinum, silver, copper or aluminum.

The sensing layer 106 is disposed on the output layer 104. The sensing layer 106 can sense different kinds of gas molecules. More specifically, the sensing layer 106 can adsorb a gas or a plurality of gases while changing its resistance value. In other words, the sensing layer 106 is equivalent to a variable resistor, and its resistance is changed by adsorbing a gas.

In some embodiments, the gas that the sensing layer 106 can sense includes NO ₂ , NH ₃ , H ₂ , CO, H ₂ O, ethanol, SO ₂ , CH ₄ , H ₂ S, O ₂ , NO, C _{2 .} H ₂ , benzene, O ₃ , Cl ₂ , methanol, acetone or a combination thereof.

The sensing material of the sensing layer 106 can be a Group IV element or an oxide thereof, such as germanium or carbon. The carbon can be a carbon nanotube or graphene. The oxide of carbon may be graphene oxide. The sensing material of the sensing layer 106 can also be a metal oxide such as zinc oxide, tin dioxide, indium oxide, tungsten trioxide, magnesium oxide, titanium dioxide, ferric oxide, or combinations thereof. In other embodiments, the sensing material of the sensing layer 106 may also be a metal, such as an Au cluster. As shown in Table 1, the sensing layer 106 can sense different kinds of gas molecules depending on the selected sensing material. Table 1

The size of the holes in the nanoporous polymer film 108 can be adjusted as needed. In other words, the size of the pores in the nanoporous polymer membrane 108 can determine the type of gas to be tested that can pass through the nanoporous polymer membrane 108. In some embodiments, the nanoporous polymer membrane 108 has minute pores that selectively pass smaller molecules and block larger molecules. For example, smaller molecules such as water, methanol, and ethanol can pass through the pores, while larger interfering substances are excluded. The type of gas to be tested that can pass through the nanoporous polymer film 108 is determined by adjusting the size of the pores in the nanoporous polymer film 108. Therefore, the nanoporous polymer film 108 can provide better protection and selectivity of the sensing layer 106, increasing the durability and functional performance of the gas sensor 100. The material of the nanoporous polymer film 108 is, for example, a perfluoro sulfonic acid polymer, a nano cellulose, a cellulose acetate, a polysulfone, a polyvinylamine, or the like. Polyamide, polyfuran or a combination thereof.

The diameter of the pores of the nanoporous polymer film 108 is, for example, 0.2 nm to 20 nm. If the pore diameter of the nanoporous polymer film 108 is too large, the selectivity of the nanoporous polymer film 108 is not good. If the pore diameter of the nanoporous polymer membrane 108 is too small, the gas molecules to be tested cannot pass through the nanoporous polymer membrane 108 to be detected. The nanoporous polymer membrane 108 has pores of appropriate size to provide a better functional performance of the gas sensor 100.

In some embodiments, the nanoporous polymer film 108 has a thickness of from 0.05 microns to 150 microns. If the thickness of the nanoporous polymer film 108 is too thick, it is difficult for the gas molecules to be tested to penetrate the nanoporous polymer film 108 to be detected. If the thickness of the nanoporous polymer film 108 is too thin, the nanoporous polymer film 108 cannot provide sufficient protection and selectivity for the gas sensor 100. The nanoporous polymer film 108 has a suitable thickness to provide the gas sensor 100 with better functional performance.

In some embodiments, the nanoporous polymer membrane 108 comprises an ionic structure. The nanoporous polymer film 108 may have an ionic functional group, and the nanoporous polymer film 108 has an ionic structure. The nanoporous polymer film 108 having an ionic structure is charged to generate an electrostatic repulsion force and increase the selectivity of the nanoporous polymer film 108. In some exemplary embodiments, the ionic functional group possessed on the nanoporous polymer membrane 108 is positively charged, and the nanoporous polymer membrane 108 is an ionic structure having a positively charged type. The nanoporous polymer membrane 108 having a positively charged ionic structure can repel the positively charged molecules and increase the selectivity of the nanoporous polymer membrane 108. In other exemplary embodiments, the ionic functional group possessed on the nanoporous polymer membrane 108 is negatively charged, and the nanoporous polymer membrane 108 is an ionic structure having a negatively charged type. The nanoporous polymer membrane 108 having a negatively charged ionic structure can repel the negatively charged molecules and increase the selectivity of the nanoporous polymer membrane 108. In the present embodiment, the material of the nanoporous polymer film 108 is, for example, a perfluorosulfonic acid polymer, and the perfluorosulfonic acid polymer is, for example, Nafion®. Nafion® has a hydrophobic backbone and a positive ion end, so Nafion® forms a nanoporous polymer membrane with a positively charged ionic structure. However, the invention is not limited thereto, and the nanoporous polymer film can also be formed by other suitable materials. In some embodiments, the pores in the nanoporous polymer membrane 108 are formed from an ionic structure. However, the invention is not limited thereto, and the pores in the nanoporous polymer film can also be formed by other suitable structures.

3 is a flow chart showing a method of manufacturing a gas sensor according to an embodiment of the present invention. Referring to FIG. 3 and FIG. 1, in step S100, an output layer 104 is formed on the substrate 102. In step S102, the sensing layer 106 is formed on the output layer 104. In step S104, a nanoporous polymer film 108 is formed on the sensing layer 106.

The gas sensor 100 described above can be completed in a single machine. In some embodiments, the step of forming the output layer 104, forming the sensing layer 106, and forming the nanoporous polymer film 108 includes three-dimensional printing. In detail, the step of forming the output layer 104 includes spraying the material of the output layer 104 onto the substrate 102. The step of forming the sensing layer 106 includes spraying the material of the sensing layer 106 onto the output layer 104. The step of forming the nanoporous polymer film 108 includes spraying a material of the nanoporous polymer film 108 onto the sensing layer 106. By forming the gas sensor of the present invention by three-dimensional printing, the desired pattern can be directly printed without being required to be formed by lithography and etching, and the cumbersome steps required for the conventional semiconductor process are omitted. In addition, damage to the formed underlying structure when forming the structure of the upper layer can be avoided. Further, by forming the gas sensor 100 of the present invention by three-dimensional printing, it is only necessary to replace the ink required to form the different members when forming the respective members. Therefore, there is no problem of cross-contamination between different materials.

Unlike conventional lithography processes, three-dimensional printing has a high degree of freedom in the configuration of the surface of the substrate 102, and the material can be formed on surfaces having various configurations. Accordingly, the substrate 102 of the gas sensor 100 of the present invention may be a planar or non-planar surface. The plane can be a smooth surface or a rough surface. Non-planar surfaces can be convex surfaces, concave surfaces, biconcave surfaces, or biconvex surfaces. The gas sensor 100 of the substrate 102 having a non-planar surface can be placed in a non-planar position or body, thus having a wider range of applications.

In some embodiments, the step of forming the nanoporous polymer film comprises three-dimensional printing and baking. In detail, after the material of the nanoporous polymer film is sprayed on the sensing layer, the baking step is followed. The baking step can make the structure of the nanoporous polymer film more stable and increase the durability of the gas sensor. In the present embodiment, the material of the nanoporous polymer film is, for example, nano cellulose. However, the invention is not limited thereto, and the nanoporous polymer film can also be formed by other suitable materials.

In some embodiments, the step of forming a nanoporous polymer film can also include a solution process. The nanoporous polymer film is formed by a solution process to provide a better fit of the nanoporous polymer film to the underlying film layer to provide better protection of the gas sensor. In the present embodiment, the material of the nanoporous polymer film is, for example, a perfluoro sulfonic acid polymer film, and the perfluorosulfonic acid polymer is, for example, Nafion®. However, the invention is not limited thereto, and the nanoporous polymer film can also be formed by other suitable materials.

In some embodiments, the step of forming a nanoporous polymer film can also include a thin film process. In this embodiment, the material of the nanoporous polymer film is, for example, cellulose acetate, polysulfone, polyvinylamine, polyamide, polyfuran or Its combination.

In summary, the nanoporous polymer membrane of the present invention has minute pores, selectively allowing smaller molecules to pass and blocking larger molecules. In addition, the nanoporous polymer membrane is located on the sensing layer of the gas sensor to provide better protection of the sensing layer. Therefore, the gas sensor of the present invention has excellent durability and functional performance.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧ gas sensor

102‧‧‧Substrate

104‧‧‧Output layer

106‧‧‧Sensor layer

108‧‧•Nano porous polymer membrane

S100, S102, S104‧‧‧ steps

1 is a schematic view of a gas sensor according to an embodiment of the present invention. 2 is a schematic cross-sectional view of a gas sensor in accordance with an embodiment of the present invention. 3 is a flow chart showing a method of manufacturing a gas sensor according to an embodiment of the present invention.

Claims (10)

A gas sensor comprising: a substrate; an output layer disposed on the substrate; a sensing layer disposed on the output layer; and a nanoporous polymer film disposed on the sensing layer. The gas sensor of claim 1, wherein the pores of the nanoporous polymer membrane have a diameter of from 0.2 nm to 20 nm. The gas sensor of claim 1, wherein the nanoporous polymer film has a thickness of from 0.05 micrometers to 150 micrometers. The gas sensor of claim 1, wherein the material of the nanoporous polymer film comprises a perfluorosulfonic acid polymer, nano cellulose, or a combination thereof. The gas sensor of claim 1, wherein the nanoporous polymer membrane comprises an ionic structure. The gas sensor of claim 1, wherein the output layer comprises an electrode. The gas sensor of claim 1, wherein the surface of the substrate comprises a plane, a rough surface, a curved surface, or a combination thereof. A method of fabricating a gas sensor, comprising: forming an output layer on a substrate; forming a sensing layer on the output layer; and forming a nanoporous polymer film on the sensing layer. The method of manufacturing a gas sensor according to claim 8, wherein the method of forming the output layer, forming the sensing layer, and forming the nanoporous polymer film comprises three-dimensional printing. The method of manufacturing a gas sensor according to claim 8, wherein the method of forming the nanoporous polymer film comprises performing a solution process.