A micro-sensor for liquid pressure measurement and contamination monitoring and a method of manufacturing the same

Abstract

The application discloses a micro sensor for liquid pressure measurement and pollution monitoring and a manufacturing method thereof. The micro sensor comprises a printed circuit board, a gallium nitride light chip arranged on the printed circuit board and used for emitting an optical signal, converting the optical signal into a photoelectric current signal and outputting a corresponding photoelectric current signal when the optical signal changes, and a polymer film arranged above the gallium nitride light chip and forming a sealed cavity with the gallium nitride light chip. The surface of the polymer film will be deformed when stressed. In the application, the liquid pressure can be detected, and whether the liquid medium is polluted can be monitored in real time.

Description

Technical Field

[0001] This invention relates to the field of semiconductor sensor technology, and more particularly to a miniature sensor for liquid pressure measurement and pollution monitoring, and its fabrication method. Background Technology

[0002] Liquid pressure measurement and water quality monitoring are closely related to human production activities. Common methods for measuring liquid pressure in daily life include liquid column gauges and elastic gauges. These two types of devices suffer from low testing accuracy, large size, difficulty in miniaturization, and certain installation requirements. While electric pressure gauges offer high testing accuracy and are easily miniaturized, they are not suitable for prolonged immersion in liquid environments, leading to data drift. For flammable liquids, electrical sensors are generally not used due to safety concerns. Utilizing fiber optic sensors for liquid pressure measurement is considered an effective method due to its high accuracy, fast response speed, and resistance to electromagnetic interference. However, the data output of fiber optic sensors requires a spectrometer, which increases operating costs, makes it difficult to manufacture portable devices, and is not suitable for on-site testing.

[0003] Liquid transport pipelines are a common application scenario for liquid pressure measurement, as the liquid pressure within the pipeline is a crucial parameter for assessing the proper functioning of the equipment. The liquid pressure measurement devices mentioned above are limited to acquiring changes in this parameter; however, they cannot monitor whether the liquid is contaminated. For example, water pollution in piped water sources in daily life cannot be monitored. Therefore, existing liquid pressure measurement devices cannot simultaneously perform both liquid pressure measurement and contamination monitoring functions.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a miniature sensor for liquid pressure measurement and pollution monitoring and its manufacturing method, so as to solve the problem that liquid pressure measurement devices cannot simultaneously perform the two functions of liquid pressure measurement and pollution monitoring.

[0006] The technical solution of the present invention is as follows:

[0007] A miniature sensor for liquid pressure measurement and contamination monitoring, comprising:

[0008] Printed circuit boards;

[0009] A gallium nitride (GaN) optical chip is disposed on the printed circuit board and is used to emit optical signals and convert optical signals into photocurrent signals, and output corresponding photocurrent signals when the optical signals change.

[0010] A polymer film is disposed above the gallium nitride (GaN) optical chip and forms a sealed cavity with the GaN optical chip; wherein the surface of the polymer film will deform when subjected to force.

[0011] In a further embodiment of the present invention, the polymer film is composed of a flexible polymer.

[0012] In a further embodiment of the present invention, the flexible polymer is one or more of polydimethylsiloxane, poly(butylene adipate / terephthalate) blend, polyurethane, polyolefin elastomer, ethylene-vinyl acetate copolymer, or polymethyl methacrylate.

[0013] In a further embodiment of the present invention, the side of the polymer film opposite to the gallium nitride optical chip is provided with an uneven microstructure.

[0014] In a further embodiment of the present invention, the thickness of the polymer film is 0.05-10 mm.

[0015] In a further embodiment of the present invention, the periphery of the surface of the polymer film is connected to the gallium nitride optical chip via epoxy resin or polydimethylsiloxane to form the closed cavity.

[0016] In a further embodiment of the present invention, the gallium nitride optical chip includes: a light source and a photodetector; the light source and the photodetector are fabricated using gallium nitride epitaxial wafers and semiconductor micro / nano fabrication processes;

[0017] The light source is used to emit light signals;

[0018] The photodetector is arranged around the light source, and the photodetector is used to receive the light signal emitted by the light source and convert it into a photocurrent signal for output.

[0019] Based on the same inventive concept, the present invention also provides a method for fabricating a miniature sensor for liquid pressure measurement and pollution monitoring as described above, comprising:

[0020] Provide printed circuit boards;

[0021] Fabrication of gallium nitride optical chips;

[0022] A polymer film is prepared and placed on top of a gallium nitride (GaN) optical chip. An epoxy resin or polydimethylsiloxane is used to connect the GaN optical chip to form a sealed cavity.

[0023] Gallium nitride optical chips are flip-chip mounted on a printed circuit board.

[0024] In a further embodiment of the present invention, the method for preparing the polymer film includes:

[0025] A template with a concave-convex microstructure is provided and the template is placed in a plastic box;

[0026] Pour the liquid, flexible polymer onto the template;

[0027] The air bubbles on the flexible polymer are removed by vacuuming, and the film formed after the flexible polymer is cured is detached from the template.

[0028] The membrane was cleaned with ethanol and then deionized water in sequence.

[0029] In a further embodiment of the present invention, the gallium nitride optical chip includes a light source and a photodetector, and the method for fabricating the gallium nitride optical chip includes:

[0030] Provide gallium nitride epitaxial wafers with the same chemical composition and structure;

[0031] Light sources and photodetectors are obtained using semiconductor micro-nano fabrication processes.

[0032] This invention provides a miniature sensor for liquid pressure measurement and pollution monitoring, and its fabrication method. The miniature sensor includes: a printed circuit board; a gallium nitride (GaN) photonic chip disposed on the printed circuit board for emitting optical signals and converting the optical signals into photocurrent signals, and outputting corresponding photocurrent signals when the optical signals change; and a polymer film disposed above the GaN photonic chip, forming a sealed cavity with the GaN photonic chip; wherein the surface of the polymer film deforms under stress. The GaN photonic chip of this invention can emit optical signals and form reflected optical signals on the surface of the polymer film, and can convert the received optical signals into photocurrent signals for output. When the sensor is subjected to the pressure of an external liquid, the polymer film above the GaN photonic chip not only undergoes physical deformation, but also the refractive index difference between the polymer film and the liquid causes significant optical changes at their interface. Therefore, when the gallium nitride (GaN) optical chip is in operation, the two changes mentioned above cause the optical signal received by the GaN optical chip to change with the liquid pressure. In addition, changes in the properties of the liquid medium (such as refractive index, turbidity, color, etc.) will also cause changes in the optical signal received by the GaN optical chip. The received optical signal is converted into a photocurrent signal. Based on the obtained photocurrent signal, the liquid pressure can be detected and the liquid medium (such as water) can be monitored in real time to see if it is contaminated. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of the miniature sensor for liquid pressure measurement and pollution monitoring in this invention.

[0035] Figure 2 This is a schematic diagram illustrating the working principle of the miniature sensor for liquid pressure measurement and pollution monitoring in this invention.

[0036] Figure 3 This is a flowchart illustrating the method for fabricating a micro-sensor for liquid pressure measurement and pollution monitoring in this invention.

[0037] Figure 4 These are optical photographs (a) and SEM images (b) of a polymer film in one embodiment of the present invention.

[0038] Figure 5 This is a graph showing the gradient change of sensor output parameters (photocurrent) with liquid pressure under different liquid media (water, oil, and ethanol) in one embodiment of the present invention.

[0039] Figure 6 This is a graph showing the reciprocating cycle curve of the sensor under a pressure of 900 kPa and a liquid medium of water in one embodiment of the present invention.

[0040] Figure 7 This is a linear relationship between the ratio of photocurrent change to water pressure and water pressure in one embodiment of the present invention when water color changes.

[0041] Figure 8 This invention provides a graph showing the relationship between the sensor output parameters (photocurrent) of a sensor without a polymer film in water and the change over time under continuous pressure.

[0042] Figure 9 This is a graph showing the relationship between the sensor output parameters (photocurrent) of a surface-integrated polymer thin film without micro / nano structures and time under different liquid media (water, oil, and ethanol) when under continuous pressure, according to one embodiment of the present invention. Detailed Implementation

[0043] This invention provides a miniature sensor for liquid pressure measurement and pollution monitoring, and a method for manufacturing the same. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0044] In the implementation methods and claims, unless otherwise specified in the text, the terms "a," "an," "the," and "the" may also include plural forms. If the embodiments of the present invention involve descriptions of "first," "second," etc., such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0045] It should be further understood that the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, "connected" or "coupled" as used herein can include wireless connections or wireless coupling. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0046] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0047] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0048] Please also refer to Figures 1 to 2 The present invention provides a preferred embodiment of a miniature sensor for liquid pressure measurement and pollution monitoring.

[0049] like Figure 1As shown, the present invention provides a miniature sensor for liquid pressure measurement and pollution monitoring, comprising: a printed circuit board 100; a gallium nitride (GaN) photonic chip 200 disposed on the printed circuit board 100 for emitting light signals and converting the light signals into photocurrent signals, and outputting corresponding photocurrent signals when the light signals change; and a polymer film 300 disposed above the GaN photonic chip 200, forming a sealed cavity with the GaN photonic chip; wherein the surface of the polymer film 300 deforms under stress.

[0050] Specifically, the gallium nitride (GaN) optical chip of this invention can emit optical signals and form reflected optical signals on the surface of the polymer film 300, and can convert the received optical signals into photocurrent signals for output, that is, it can realize the mutual conversion between optical signals and electrical signals. The side of the polymer film 300 opposite to the GaN optical chip 200 has a certain distance from the surface of the GaN optical chip 200 and forms a closed, sealed cavity with the GaN optical chip 200, which can prevent the intrusion of external liquids. When the sensor is subjected to the pressure of an external liquid, the polymer film 300 above the GaN optical chip 200 will not only undergo physical deformation, but also the refractive index difference between the polymer film 300 and the liquid will cause significant optical changes at their interface. Therefore, when the gallium nitride (GaN) photonic chip 200 is in operation, the two changes mentioned above cause the light signal received by the GaN photonic chip 200 to change with the liquid pressure. In addition, changes in the properties of the liquid medium (such as refractive index, turbidity, color, etc.) will also cause changes in the light signal received by the GaN photonic chip 200. The received light signal is converted into a photocurrent signal. Based on the obtained photocurrent signal, the liquid pressure can be detected and the liquid medium (such as water) can be monitored in real time for contamination. In other words, the miniature sensor provided by this invention realizes the measurement of liquid pressure and the real-time monitoring of liquid contamination. Moreover, this invention uses photoelectric signals for measurement or monitoring, which not only has wide applicability but also high testing accuracy and fast response.

[0051] In a further embodiment of one example, the polymer film 300 is made of a flexible polymer so that the surface of the polymer film 300 can deform when subjected to external pressure.

[0052] In some embodiments, the flexible polymer is one or more of polydimethylsiloxane, polybutylene adipate / terephthalate blend (Ecoflex), polyurethane (PU), polyolefin elastomer (POE), ethylene-vinyl acetate copolymer (EVA), or polymethyl methacrylate (PMMA), for example, it may be polydimethylsiloxane.

[0053] In some embodiments, the thickness of the polymer film 300 is 0.05-10 mm, for example, it can be 0.3 mm, 0.5 mm, 1 mm, 3 mm, 5 mm, or 10 mm. The thinner the polymer film, the easier it is to deform under stress and the faster the response speed.

[0054] In a further embodiment of one example, the polymer film 300 has an uneven microstructure on the side opposite to the gallium nitride optical chip 200.

[0055] Specifically, the polymer film 300 has a concave-convex microstructure on the side opposite to the gallium nitride optical chip 200. The polymer film 300 with the concave-convex microstructure has different light scattering capabilities, which can enhance the propagation of the light path on the gallium nitride optical chip 200, thereby improving the sensitivity of the micro sensor to changes in liquid pressure and pollution (such as changes in water quality).

[0056] In a further embodiment of one example, the periphery of the surface of the polymer film 300 is connected to the gallium nitride optical chip 200 via epoxy resin or polydimethylsiloxane to form the enclosed cavity.

[0057] Specifically, the polymer film 300 does not directly contact the surface of the gallium nitride optical chip 200. Instead, the polymer film 300 is sealed with epoxy resin or PMDS around the gallium nitride optical chip 200, so that the polymer film 300 and the gallium nitride optical chip 200 form a sealed cavity to prevent external liquids from entering and damaging the gallium nitride optical chip.

[0058] Please see Figure 1 and Figure 2 In some embodiments, the gallium nitride optical chip 200 includes: a light source 201 and a photodetector 202; the light source 201 and the photodetector 202 are made of gallium nitride epitaxial wafers and semiconductor micro-nano processing technology; the light source 201 is used to emit light signals; the photodetector 202 is arranged around the light source 201, and the photodetector 202 is used to receive the light signals emitted by the light source 201 and convert them into photocurrent signals for output.

[0059] Specifically, the gallium nitride (GaN) optical chip 200 integrates a light source 201 and a photodetector 202 to achieve mutual conversion between optical and electrical signals. This facilitates sensor miniaturization, reduces power consumption, lowers costs, and is suitable for mass production. The GaN optical chip 200 is flip-chip packaged on a printed circuit board. The light source 201 is powered by a power supply device; in one implementation, the power supply device can be an adjustable power supply. The photodetector 202 is connected to a photocurrent signal reading device, which reads the photocurrent signal output by the photodetector. In one implementation, the photocurrent signal reading device can be a digital source meter.

[0060] The photodetector 202 is arranged around the light source 201, which is beneficial for receiving the light signal emitted by the light source. Of course, the light source 201 and the photodetector 202 can also be arranged side by side, or the light source 201 can be arranged around the photodetector 202.

[0061] Please see Figure 3 In some embodiments, the present invention also provides a method for fabricating a miniature sensor for liquid pressure measurement and pollution monitoring as described above, comprising the steps of:

[0062] S100, provides printed circuit boards;

[0063] S200, fabrication of gallium nitride optical chips;

[0064] S300: Prepare a polymer film and use epoxy resin or polydimethylsiloxane to connect the polymer film to the upper surface of the gallium nitride optical chip to form a sealed cavity.

[0065] S400: The gallium nitride optical chip is flip-mounted onto the printed circuit board.

[0066] Specifically, the gallium nitride (GaN) optical chip can emit optical signals and form reflected optical signals on the surface of a polymer film, and can convert the received optical signals into photocurrent signals for output, thus realizing the mutual conversion between optical signals and electrical signals. The GaN optical chip is mounted on a printed circuit board using a flip-chip process. The side of the polymer film opposite the GaN optical chip has a certain distance from the surface of the GaN optical chip and forms a closed, sealed cavity with the GaN optical chip, preventing the intrusion of external liquids.

[0067] When the sensor is subjected to the pressure of an external liquid, the polymer film above the gallium nitride (GaN) photonic chip undergoes physical deformation. Simultaneously, the refractive index difference between the polymer film and the liquid causes significant optical changes at their interface. Therefore, when the GaN photonic chip is in operation, these two changes cause the received optical signal to vary with the liquid pressure. Furthermore, changes in the properties of the liquid medium (such as refractive index, turbidity, and color) also cause changes in the received optical signal. This received optical signal is converted into a photocurrent signal. Based on the obtained photocurrent signal, liquid pressure can be detected, and the contamination of the liquid medium (such as water) can be monitored in real time. In other words, the miniature sensor provided by this invention achieves the measurement of liquid pressure and real-time monitoring of liquid contamination. Moreover, this invention uses photoelectric signals for measurement or monitoring, which not only has wide applicability but also high testing accuracy and fast response.

[0068] In some embodiments, the gallium nitride optical chip includes a light source and a photodetector, and the method for fabricating the gallium nitride optical chip includes:

[0069] S201, Provide gallium nitride epitaxial wafers with the same chemical composition and structure;

[0070] S202. Light sources and photodetectors are obtained using semiconductor micro-nano fabrication technology.

[0071] Specifically, the light source and photodetector are fabricated using semiconductor micro / nano fabrication processes (including photolithography, dry etching, thin film deposition, and laser cutting) on ​​the same GaN epitaxial wafer with the same chemical composition and structure (with buffer GaN, n-type GaN, InGaN / GaN quantum hydrazine, and p-type GaN thin films deposited from top to bottom on a sapphire substrate). The light source and photodetector have the same chemical composition and structure, and their respective effective areas and patterns are defined by photolithography, allowing for flexible adjustment according to actual needs. The light source and photodetector are located on the same plane, have the same chemical composition and structure, and are electrically insulated from each other.

[0072] In some embodiments, the method for preparing the polymer film includes:

[0073] S301. Provide a template with a concave-convex microstructure and place the template in a plastic box;

[0074] S302. Pour the liquid flexible polymer onto the template;

[0075] S303. Remove air bubbles from the flexible polymer by vacuuming and detach the film formed by the cured flexible polymer from the template.

[0076] S304. Clean the membrane with ethanol and then with deionized water in sequence.

[0077] Specifically, the template can be sandpaper or a porous material. The sandpaper has a mesh size of 40-5000, such as 40, 2000, or 5000. The higher the mesh size of the sandpaper, the more pronounced the uneven microstructure on the resulting polymer film. The porous material has a pore size L ≥ 0.2 micrometers, such as 300 or 500 micrometers. The larger the pore size of the porous material, the more pronounced the uneven microstructure on the resulting polymer film. The porous material can be synthetic or natural. Synthetic materials can be foamed plastics or foamed metals, while natural materials can be oyster shells or potato leaves. In practice, the template made of sandpaper or porous material is placed in a plastic box. A certain amount of liquid polydimethylsiloxane (PPS) precursor before curing is poured onto the template. Air bubbles are removed by vacuuming. Subsequently, heating or cooling is selected based on the characteristics of the polymer material to cure the film. After the film is detached from the template, it is cleaned sequentially with ethanol and deionized water to obtain a polymer film of a certain thickness.

[0078] Example 1

[0079] Cut a 2*2cm piece from 2000-grit sandpaper. 2 The film was placed in a 10ml plastic box. 2g of the uncured precursor of liquid polydimethylsiloxane (PDMS) was poured onto the surface of sandpaper. Air bubbles were then removed quickly by vacuuming for 0.5-1 hour. After 12 hours of natural curing, the film was removed from the sandpaper and cleaned sequentially with ethanol and deionized water. The resulting film thickness was 0.5mm. Optical photographs of the film are shown below. Figure 4 As shown in (a), the planar SEM (scanning electron microscope) results are as follows: Figure 4 As shown in (b), the uneven surface texture and light scattering of the thin film are clearly visible. After the polymer thin film is prepared, the side of the film with the uneven microstructure is placed on top of the GaN optical chip, and the film is sealed with PDMS to form a closed cavity between the film and the GaN chip.

[0080] Example 2

[0081] Cut a 2*2cm piece of 40-grit sandpaper. 2The film was placed in a 10ml plastic box, and 0.2g of the liquid polydimethylsiloxane (PDMS) precursor before curing was poured onto the surface of sandpaper. Air bubbles were removed quickly by vacuuming for 0.5-1 hour. After 12 hours of natural curing, the film was removed from the sandpaper and cleaned sequentially with ethanol and deionized water to obtain a film thickness of 0.5mm. The side of the film with its uneven microstructure was placed on top of the GaN optical chip, and the film was sealed with epoxy resin to form a closed cavity between the film and the GaN chip.

[0082] Example 3

[0083] Cut a 1*1cm piece from 5000-grit sandpaper. 2 The film was placed in a 5ml plastic box, and 10g of the liquid polydimethylsiloxane (PDMS) precursor before curing was poured onto the surface of sandpaper. Air bubbles were removed quickly by vacuuming for 0.5-1 hour. After 24 hours of natural curing, the film was removed from the sandpaper and cleaned sequentially with ethanol and deionized water to obtain a film thickness of 10mm. The side of the film with its uneven microstructure was placed on top of the GaN optical chip, and the film was sealed with PDMS to form a closed cavity between the film and the GaN chip.

[0084] Example 4

[0085] Cut a 1*1cm piece from a foam plastic with an average pore size of 300um. 2 A 1mm thick film was placed in a 5ml plastic box. 2g of the pre-cured poly(ethylene adipate) / butyl terephthalate (Ecoflex) blend was poured onto the surface of a foam plastic film. Air bubbles were removed quickly by vacuuming for 0.5-1 hour. The film was then dried and cured at 60℃ on a heating table. The film was then detached from the foam plastic film and cleaned sequentially with ethanol and deionized water. The resulting film thickness was 0.3mm. The side of the film with its uneven microstructure was placed on top of the GaN optical chip, and the film was sealed with epoxy resin to form a closed cavity between the film and the GaN chip.

[0086] Example 5

[0087] The foam metal with an average pore size of 500 μm was cut into 1*1 cm pieces. 2A 2mm thick film was placed in a 5ml plastic box. 10g of polymethyl methacrylate (PMMA) precursor, before curing, was poured onto the surface of a foamed metal. Air bubbles were removed quickly by vacuuming for 0.5-1 hour, followed by cooling and curing. The film was then detached from the foamed metal and cleaned sequentially with ethanol and deionized oil, resulting in a 3mm thick film. The side of the film with its uneven microstructure was placed on top of a GaN optical chip, and the film was sealed with epoxy resin to form a closed cavity between the film and the GaN chip.

[0088] Example 6

[0089] Cut the oyster shells from nature into 2*2cm pieces. 2 The film was placed in a 5ml plastic box, and 10g of the uncured polyolefin elastomer (POE) precursor was poured onto the surface of an oyster shell. Air bubbles were removed quickly by vacuuming for 0.5-1 hour, followed by cooling and curing. The film was then detached from the oyster shell and cleaned sequentially with ethanol and deionized water, resulting in a film thickness of 5mm. The side of the film with its uneven microstructure was placed on top of a GaN optical chip, and the film was sealed with epoxy resin to form a closed cavity between the film and the chip.

[0090] Example 7

[0091] Cut the potato leaves from nature into 2*2cm pieces. 2 The film was placed in a 5ml plastic box, and 3g of the pre-cured polyurethane (PU) precursor was poured onto the surface of the oyster shell. Air bubbles were removed quickly by vacuuming for 0.5-1 hour, followed by curing. The film was then detached from the potato leaves and cleaned sequentially with ethanol and deionized oil, resulting in a film thickness of 1mm. The side of the film with its uneven microstructure was placed on top of the GaN optical chip, and the film was sealed with epoxy resin to form a closed cavity between the film and the GaN chip.

[0092] To better understand the present invention, the following examples illustrate the placement of the polymer film sensor prepared in Example 1 in pressure testing equipment with water, silicone oil, and ethanol as liquid media. Figure 5 (a, b, c) show the gradient changes of sensor output parameters (photocurrent) with liquid pressure under different liquid media (water, oil, and ethanol). It can be clearly seen from the figure that the initial value and change of photocurrent are different under different liquid media, and the change of liquid pressure is very obvious, and there is a negligible hysteresis. Figure 6The graph presented shows the reciprocating cycle curve of the sensor under a pressure of 900 kPa and a liquid medium of water, indicating excellent sensor stability. To demonstrate that the sensor can measure both liquid pressure and water quality, the linear relationship between the photocurrent change ratio and water pressure changes significantly under different pressures when the water undergoes changes (e.g., refractive index, turbidity, color). The results are as follows. Figure 7 As shown, the abrupt change in photocurrent value under corresponding water pressure can reflect whether the water quality is polluted. Therefore, the sensor provided by this invention can quickly and effectively realize the functions of liquid pressure measurement and real-time monitoring of liquid pollution, and has broad application prospects.

[0093] To demonstrate that gallium nitride optical chips without polymer films are almost unaffected by changes in liquid pressure, a comparative example is provided below:

[0094] A gallium nitride (GaN) photonic chip without a polymer thin film structure was directly placed in a pressure testing device with water as the liquid medium. The changes in sensor output parameters (photocurrent) over time under continuous pressure in different liquid media (water, oil, and ethanol) were investigated. Figure 8 It is evident from the above that a single gallium nitride photonic chip has almost no response to changes in liquid pressure.

[0095] To demonstrate that the micro / nano structure of polymer films enhances the sensitivity of microsensors to changes in liquid pressure and contamination, a comparative example is provided below:

[0096] Pour 2g of the uncured liquid polydimethylsiloxane (PDMS) precursor directly onto a smooth, flat surface in a 10ml plastic container. Remove air bubbles quickly by vacuuming for 0.5-1 hour. After 12 hours of natural curing, remove the film from the sandpaper and clean it sequentially with ethanol and deionized water. The resulting film thickness is 0.5µm. Place the planar film on top of the GaN chip and seal the film perimeter with PDMS to form a sealed cavity. Place the completed sensor in pressure testing equipment with water, silicone oil, and ethanol as the liquid media. Please refer to [link to relevant documentation]. Figure 9 , Figure 9 List the linear relationship between sensor output parameters (photocurrent) and liquid pressure under different liquid media (water, oil, and ethanol), from... Figure 9 It can be clearly seen that the pressure range of a smooth planar thin film varies little, and it changes abruptly within a small range. It is very unstable under the same test parameters. The comparative results show that polymer thin films with micro-nano structures can effectively improve the pressure measurement range and stability of the sensor.

[0097] In summary, the miniature sensor for liquid pressure measurement and pollution monitoring and its fabrication method provided by this invention have the following beneficial effects:

[0098] It enables the measurement of liquid pressure and real-time monitoring of liquid contamination;

[0099] It is not only widely applicable, highly accurate in testing, fast in response, easy to miniaturize and low in power consumption, but also has a low production cost, making it suitable for mass production.

[0100] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A miniature sensor for liquid pressure measurement and pollution monitoring, characterized in that, include: Printed circuit boards; A gallium nitride (GaN) optical chip is disposed on the printed circuit board and is used to emit optical signals and convert optical signals into photocurrent signals, and output corresponding photocurrent signals when the optical signals change; the GaN optical chip is mounted on the printed circuit board using a flip-chip process. A polymer film is disposed above the gallium nitride (GaN) optical chip and forms a sealed cavity with the GaN optical chip; wherein the surface of the polymer film deforms when subjected to force. When the sensor is subjected to the pressure of an external liquid, the polymer film above the gallium nitride (GaN) optical chip will not only undergo physical deformation, but also the two media, the polymer film and the liquid, will generate a refractive index difference. When the GaN optical chip is in operation, the above two changes cause the optical signal received by the GaN optical chip to change with the liquid pressure. In addition, changes in the properties of the liquid medium will also cause changes in the optical signal received by the GaN optical chip.

2. The miniature sensor for liquid pressure measurement and pollution monitoring according to claim 1, characterized in that, The polymer film is composed of a flexible polymer.

3. The miniature sensor for liquid pressure measurement and pollution monitoring according to claim 2, characterized in that, The flexible polymer is one or more of the following: polydimethylsiloxane, poly(butylene adipate / terephthalate) blend, polyurethane, polyolefin elastomer, ethylene-vinyl acetate copolymer, or polymethyl methacrylate.

4. The miniature sensor for liquid pressure measurement and pollution monitoring according to any one of claims 1-3, characterized in that, The polymer film has a concave-convex microstructure on the side opposite to the gallium nitride optical chip.

5. The miniature sensor for liquid pressure measurement and pollution monitoring according to any one of claims 1-3, characterized in that, The thickness of the polymer film is 0.05-10 mm.

6. The miniature sensor for liquid pressure measurement and pollution monitoring according to claim 1, characterized in that, The surface of the polymer film is connected to the gallium nitride optical chip via epoxy resin or polydimethylsiloxane to form the sealed cavity.

7. The miniature sensor for liquid pressure measurement and pollution monitoring according to claim 1, characterized in that, The gallium nitride optical chip includes: a light source and a photodetector; the light source and the photodetector are fabricated using gallium nitride epitaxial wafers and semiconductor micro-nano processing technology; The light source is used to emit light signals; The photodetector is arranged around the light source, and the photodetector is used to receive the light signal emitted by the light source and convert it into a photocurrent signal for output.

8. A method for manufacturing a miniature sensor for liquid pressure measurement and pollution monitoring according to any one of claims 1-7, characterized in that, include: Provide printed circuit boards; Fabrication of gallium nitride optical chips; A polymer film is prepared and connected to the upper surface of a gallium nitride optical chip using epoxy resin or polydimethylsiloxane to form a sealed cavity. Gallium nitride optical chips are flip-chip mounted on a printed circuit board.

9. The method for fabricating a miniature sensor for liquid pressure measurement and pollution monitoring according to claim 8, characterized in that, The method for preparing the polymer film includes: A template with a concave-convex microstructure is provided and the template is placed in a plastic box; Pour the liquid, flexible polymer onto the template; The air bubbles on the flexible polymer are removed by vacuuming, and the film formed after the flexible polymer is cured is detached from the template. The membrane was cleaned with ethanol and then deionized water in sequence.

10. The method for fabricating a micro-sensor for liquid pressure measurement and pollution monitoring according to claim 8, characterized in that, The gallium nitride optical chip includes a light source and a photodetector, and the method for fabricating the gallium nitride optical chip includes: Provide gallium nitride epitaxial wafers with the same chemical composition and structure; Light sources and photodetectors are obtained using semiconductor micro-nano fabrication processes.

Images