Micro-fluidic water quality sensor based on MEMS and detection method thereof

Abstract

The invention discloses a micro-fluidic water quality sensor based on MEMS and a detection method thereof, and belongs to the technical field of water quality monitoring chips, the micro-fluidic water quality sensor comprises a substrate, a micro-fluidic channel is arranged in the middle of the substrate, a detection assembly is arranged on one side of the micro-fluidic channel, and a heating electrode is arranged at the bottom of the micro-fluidic channel; according to the sensor, microfluid control, local heating evaporation, spectrum detection and intelligent control strategies are comprehensively applied, rapid and accurate analysis of water quality parameters is achieved, the sensitivity and response speed of a water quality monitoring technology are improved, the microminiaturization degree of the sensor is improved by applying an MEMS technology, and the sensor is particularly suitable for the field of on-site instant detection and environment monitoring; the assembling and manufacturing of the sensor not only detailedly describes the whole process from material selection, structural design to assembly integration, but also emphasizes the key control point and optimization strategy of each step, so as to achieve the batch production target of the efficient and reliable microfluidic water quality sensor.

Description

Technical Field

[0001] The present application belongs to the technical field of water quality monitoring chips, and in particular, relates to a MEMS microfluidic water quality sensor and a detection method thereof. Background Art

[0002] In recent years, microfluidic chip technology has been widely recognized by countries around the world for its fast analysis speed, low consumption, small size and simple operation. This technology is based on a microchannel network and is based on microelectromechanical systems (MEMS). It integrates the functions of the entire laboratory on a tiny chip, forming the so-called "chip laboratory". At present, the development of microfluidic chips is mainly focused on instrument miniaturization, system integration, different chip materials and a variety of detection technologies. With the continuous development of microfluidic chips, high-speed multi-channel detection devices, low-cost equipment and highly versatile microfluidic detection chips that integrate a variety of methods will become the future development direction.

[0003] Microfluidics is a technology for precisely controlling and manipulating microscale fluids. Through this technology, researchers can integrate basic operating units such as sample preparation, reaction, separation, and detection onto a centimeter-level chip. This technology is generally used in the analysis of trace drugs in the fields of biology, chemistry, and pharmaceuticals. It mainly involves the transport and mixing of trace reagents. This technology is of great significance to the development of biomedicine, drug diagnosis, food hygiene, environmental monitoring, and molecular biology.

[0004] Existing water quality monitoring methods have room for improvement in terms of sensitivity, response speed and miniaturization. The present invention aims to solve this problem and design and manufacture a highly integrated and intelligent microfluidic water quality sensor. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a water quality sensor based on MEMS microfluidics to solve the technical problems of low sensitivity, low response speed and low degree of miniaturization of existing water quality monitoring technologies.

[0006] To achieve the above-mentioned purpose, the technical solution adopted in this application is: to provide a MEMS microfluidic water quality sensor, including a substrate, a microfluidic channel is provided in the middle of the substrate, a detection component is provided on one side of the microfluidic channel, and a heating electrode is provided at the bottom of the microfluidic channel.

[0007] In one embodiment,

[0008] The substrate includes an upper layer, a middle layer and a lower layer, the upper layer is a hydrophobic protective layer, the middle layer is an insulating medium layer, the lower layer is a base glass layer, and an electrode array layer is arranged on the base glass layer; metal tentacles are arranged at the bottom of the substrate, and the number of the metal tentacles is at least 1, and preferably, the number of the metal tentacles is 12.

[0009] In one embodiment,

[0010] The microfluidic channel is located in the silicon-based conductive layer.

[0011] In one embodiment,

[0012] A heating electrode groove is etched on the base glass layer, the heating electrode is arranged in the heating electrode groove, and the heating electrode is in a serpentine shape.

[0013] In one embodiment,

[0014] The insulating dielectric layer material is one of silicon oxide, silicon nitride or aluminum oxide, and the insulating dielectric layer thickness is 100-200nm, preferably, the insulating dielectric layer thickness is 165nm; the hydrophobic protective layer material is polytetrafluoroethylene; the silicon-based conductive layer material is indium tin oxide conductive glass.

[0015] In one embodiment,

[0016] The detection component comprises a waveguide cavity, a light guide grid is arranged inside the waveguide cavity, and the number of the light guide grid is at least one group; an ultraviolet light source and a silicon photocell are arranged on one side of the waveguide cavity.

[0017] In one embodiment,

[0018] The ultraviolet light source comprises an ultraviolet light emitting module, and the ultraviolet light emitting module is provided with a light emitting unit, and the number of the light emitting unit is at least one.

[0019] In one embodiment,

[0020] The ultraviolet light emitting module adopts a mixture of two of gallium arsenide, cadmium sulfide, indium phosphide or zinc sulfide, and the wavelength of the light emitting unit is 365-405nm.

[0021] In one embodiment,

[0022] The light guide grid material is one of fused quartz, calcium fluoride, magnesium fluoride, ultraviolet fused amorphous silicon dioxide, germanium or zinc selenide; the light guide grid is arranged parallel to the substrate, and the ultraviolet light source passes through the waveguide cavity into the microfluidic channel.

[0023] The present application also provides a detection method based on a MEMS microfluidic water quality sensor, which specifically includes the following steps:

[0024] (i) Pretreatment: injecting a liquid sample into the microfluidic channel and heating the liquid sample by controlling the temperature using a heating electrode;

[0025] (ii) Excitation light source: when performing electrical control, the ultraviolet light source at the location of the liquid to be detected is controlled to emit ultraviolet light of a preset band, which is guided by the waveguide cavity so that the ultraviolet light penetrates or irradiates the detection liquid, thereby exciting the target compound in the detection liquid to produce an optical response;

[0026] (III) Collecting detection information: turning on the first ultraviolet light source, and controlling the heating electrodes around the position of the droplet to be detected, and closing them in sequence along the detection direction; further collecting the light reflected, scattered or fluorescent by the sample, and when turning on the second ultraviolet light source, turning off the first ultraviolet light source, controlling the heating electrodes around the position of the droplet to be detected, and closing them in sequence along the detection direction, recovering them through the waveguide cavity and the optical grid and guiding them to the silicon photocell;

[0027] (IV) Information processing: Silicon photocells convert received optical signals into electrical signals, amplify and process the signals to identify and quantify specific components or properties in the sample; based on the intensity, waveform or other characteristic parameters of the electrical signal, combined with a preset calibration curve or algorithm, the component concentration, purity or specific physical and chemical parameters of the liquid to be tested are analyzed and obtained.

[0028] The present application provides a water quality sensor based on MEMS microfluidics, which innovatively forms a microfluidic channel on a substrate to guide the flow of the liquid to be tested, ensure effective contact between the sample and the detection area, and accurately heat the liquid to be tested with a heating electrode, and guide the light source through a waveguide optical cavity in conjunction with ultraviolet light detection; the sensor comprehensively utilizes microfluidic manipulation, local heating evaporation, spectral detection, and intelligent control strategies to achieve rapid and accurate analysis of water quality parameters, improve the sensitivity and response speed of water quality monitoring technology, and use MEMS technology to increase the degree of miniaturization of the sensor, making it particularly suitable for on-site instant detection and environmental monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 It is the top view of the sensor;

[0031] Figure 2 is a side cross-sectional view of the sensor;

[0032] Figure 3 Schematic diagram of the base.

[0033] Explanation of symbols in the figure:

[0034] 1. Substrate; 2. Heating electrode; 3. Ultraviolet light source; 4. Silicon photocell; 5. Waveguide cavity; 6. Insulating dielectric layer; 7. Hydrophobic protective layer; 8. Light guide grid; 9. Microfluidic channel; 10. Metal tentacles; 11. Substrate glass layer. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear, the present application is further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] Example 1

[0037] A water quality sensor based on MEMS microfluidics, such as Figure 1-2 As shown, it includes a substrate 1, a microfluidic channel 9 is provided in the middle of the substrate 1, a detection component is provided on one side of the microfluidic channel 9, and a heating electrode 2 is provided at the bottom of the microfluidic channel 9; Figure 3 As shown, the substrate 1 includes an upper layer, a middle layer and a lower layer, the upper layer is a hydrophobic protective layer 7, the middle layer is an insulating medium layer 6, the insulating medium layer 6 covers the top of the structure, and the lower layer is a base glass layer 11, on which an electrode array layer is provided; the microfluidic channel 9 is located in the silicon-based conductive layer, a heating electrode groove is etched on the base glass layer 11, and the heating electrode 2 is provided in the heating electrode groove; the detection component includes a waveguide optical cavity 5, a light guide grid 8 is provided inside the waveguide optical cavity 5, and an ultraviolet light source 3 and a silicon photocell 4 are provided on one side of the waveguide optical cavity 5.

[0038] Specifically, the substrate 1 serves as the basic supporting structure of the sensor and provides a stable platform for the microfluidic channel 9 and the heating electrode 2. The hydrophobic protective layer 7 is made of polytetrafluoroethylene and is used to maintain the stable flow of liquid in the microfluidic channel 9 to avoid cross contamination. The hydrophobic protective layer 7 covers the non-detection area (the detection area refers to the area where the microfluidic channel 9 is located; the insulating medium layer 6 covers the non-detection area on the periphery of the silicon-based conductive layer, and only leaks out the detection area); the insulating medium layer 6 is a hydrophilic porous medium layer made of aluminum oxide material, which not only isolates and protects the circuit below, but also assists in the transmission of optical signals, and has a thickness of 165nm; the silicon-based conductive layer material is indium tin oxide conductive glass; the substrate glass layer 11 is made of a high-transparency, high-temperature resistant material; the electrode array layer is connected to the heating electrode 2;

[0039] The microfluidic channel 9 is located in the silicon-based conductive layer and connected to the optical grid 8. The microfluidic channel 9 is designed to be micrometer-level to guide the flow of the liquid to be tested and ensure effective contact between the sample and the detection area. The heating electrode 2 is located at the bottom of the microfluidic channel 9, with a gap in the middle, and the gap forms a liquid evaporation channel. The heating electrode 2 is serpentine. The serpentine design can increase the heat exchange area, accurately control the heating area, and achieve local rapid heating of the liquid flowing through, promote the evaporation of specific substances and / or enhance their optical properties, so as to prepare for subsequent optical detection.

[0040] The waveguide cavity 5 is used to guide the ultraviolet light to accurately reach and pass through the microfluidic channel 9, and collect the light reflected by the liquid to ensure the efficient transmission of the light path; the number of the light guide grid 8 is at least one group, and in this embodiment, there are two groups, and the material is ultraviolet molten amorphous silicon dioxide. The light guide grid 8 is arranged opposite to the substrate 1 in parallel, and is used for the effective guidance and collection of the optical signal. The light guide grid 8 is connected to the microfluidic channel 9 to form a detection light source channel;

[0041] The ultraviolet light source 3 includes an ultraviolet light emitting module, which uses a mixture of indium phosphide and gallium arsenide, and the mixing ratio of indium phosphide to gallium arsenide is 4:1; a light-emitting unit is provided on the ultraviolet light emitting module, and the number of the light-emitting units is at least 1, and in this embodiment, there are two, which are divided into a first light-emitting unit and a second light-emitting unit, the wavelength of the first light-emitting unit is 385nm, and the wavelength of the second light-emitting unit is 405nm, the ultraviolet light source 3 is connected to the waveguide cavity 5, and the ultraviolet light source 3 passes through the waveguide cavity 5 into the microfluidic channel 9, and can emit ultraviolet light of a specific band to the waveguide cavity 5 for exciting substances in the liquid to be tested; the silicon photocell 4 is arranged at the receiving end, and is used to capture the light signal reflected or scattered after the substance in the liquid is excited, and convert it into an electrical signal;

[0042] The working principle of the MEMS microfluidic water quality sensor: During the operation, the liquid to be tested is first sent into the microfluidic channel 9 through a micro-injection pump, the heating electrode 2 is started, and the fluid is heated as needed. At the same time, the ultraviolet light source 3 emits ultraviolet light, which is introduced into and passes through the fluid through the waveguide cavity 5 to stimulate the substance to be tested to produce an optical response. The response light is then collected by the waveguide cavity 5 and guided to the silicon photocell 4. The silicon photocell 4 converts the received optical signal into an electrical signal, which carries information on water quality parameters.

[0043] The assembly and manufacturing of MEMS microfluidic water quality sensor includes the following steps:

[0044] 1. The microchannel structures of the sample microfluidic channel 9 and the heating electrode 2 are processed on the polydimethylsiloxane substrate using soft lithography technology.

[0045] 2. The porous foamed carbon is prepared by chemical reaction and heat treatment as the substrate 1 of the hydrophilic porous medium layer to ensure good liquid suction capability.

[0046] 3. A hydrophobic protective layer 7 is formed by spraying polytetrafluoroethylene emulsion on the hydrophilic porous medium layer to ensure stable flow of the liquid in the channel.

[0047] 4. Assemble the components, place the insulating dielectric layer 6 on the substrate, seal the edges with uncured polymethylhydrogensiloxane, and finally assemble the cover. Use plasma treatment to enhance the bonding between the layers to ensure the sealing and stability of the device.

[0048] 5. Sealing and bonding: Use uncured polymethylhydrogensiloxane material to seal the edges of all components to ensure that there is no liquid leakage path. After sealing, place the entire assembly in an oxygen plasma environment for surface treatment to enhance the adhesion between the layers, followed by high-temperature curing to complete the final packaging to ensure the airtightness and long-term stability of the sensor.

[0049] Example 2

[0050] A detection method based on a MEMS microfluidic water quality sensor specifically comprises the following steps:

[0051] (i) Pretreatment: injecting a liquid sample into the microfluidic channel 9, and heating the liquid sample by using the heating electrode 2;

[0052] (ii) Excitation light source: when performing electrical control, the ultraviolet light source 3 at the location of the liquid to be detected is controlled to emit ultraviolet light of a preset band, which is guided by the waveguide cavity 5 so that the ultraviolet light penetrates or irradiates the detection liquid, thereby exciting the target compound in the detection liquid to produce an optical response;

[0053] (III) Collecting detection information: Turning on the first ultraviolet light source, and controlling the heating electrodes 2 around the position of the droplet to be detected, and closing them in sequence along the detection direction; further collecting the light reflected, scattered or fluorescent by the sample, and when turning on the second ultraviolet light source, turning off the first ultraviolet light source, controlling the heating electrodes 2 around the position of the droplet to be detected, and closing them in sequence along the detection direction, recovering them through the waveguide cavity 5 and the optical grid 8 and guiding them to the silicon photocell 4;

[0054] (IV) Information processing: The silicon photocell 4 converts the received optical signal into an electrical signal, amplifies and processes the signal to identify and quantify specific components or properties in the sample; based on the intensity, waveform or other characteristic parameters of the electrical signal, combined with a preset calibration curve or algorithm, the component concentration, purity or specific physical and chemical parameters of the liquid to be tested are analyzed and obtained.

[0055] Example 3

[0056] The present embodiment is different from the first embodiment in that the insulating dielectric layer 6 is made of silicon oxide, and the rest of the configuration is the same.

[0057] Example 4

[0058] The present embodiment is different from the first embodiment in that the insulating dielectric layer 6 is made of silicon oxide, and the rest of the configuration is the same.

[0059] Example 5

[0060] The difference between this embodiment and the first embodiment is that the thickness of the insulating dielectric layer 6 is 100 nm, and the other configurations are the same.

[0061] Example 6

[0062] The difference between this embodiment and embodiment 1 is that the thickness of the insulating dielectric layer 6 is 200 nm, and the other configurations are the same.

[0063] Example 7

[0064] The difference between this embodiment and the first embodiment is that the material of the light guide grid 8 is fused quartz, and the other configurations are the same.

[0065] Example 8

[0066] The present embodiment is different from the first embodiment in that the material of the light guide grid 8 is calcium fluoride, and the rest of the configuration is the same.

[0067] Example 9

[0068] The present embodiment is different from the first embodiment in that the material of the light guide grid 8 is magnesium fluoride, and the rest of the configuration is the same.

[0069] Example 10

[0070] The present embodiment is different from the first embodiment in that the material of the light guide grid 8 is germanium, and the other configurations are the same.

[0071] Embodiment 11

[0072] The present embodiment is different from the first embodiment in that the material of the light guide grid 8 is zinc selenide, and the rest of the configuration is the same.

[0073] Example 12

[0074] The present embodiment is different from the first embodiment in that the ultraviolet light emission module uses a mixture of cadmium sulfide and zinc sulfide, and the other configurations are the same.

[0075] Embodiment 13

[0076] The present embodiment is different from the first embodiment in that the ultraviolet light emission module adopts a mixture of cadmium sulfide and gallium arsenide, and the rest of the configuration is the same.

[0077] The present application provides a water quality sensor based on MEMS microfluidics, comprising a substrate, a microfluidic channel in the middle of the substrate, a detection component on one side of the microfluidic channel, and a heating electrode at the bottom of the microfluidic channel; the present application innovatively forms a microfluidic channel on the substrate to guide the flow of the liquid to be tested and ensure effective contact between the sample and the detection area; the heating electrode accurately heats the liquid to be tested, and cooperates with ultraviolet light detection to guide the light source through a waveguide optical cavity; the sensor comprehensively uses microfluidic manipulation, local heating evaporation, spectral detection and intelligent control strategies to achieve rapid and accurate analysis of water quality parameters, improve the sensitivity and response speed of water quality monitoring technology, and use MEMS technology to improve the miniaturization of the sensor, which is particularly suitable for on-site instant detection and environmental monitoring fields; the assembly and manufacture of the sensor not only describes in detail the entire process from material selection, structural design to component integration, but also emphasizes the key control points and optimization strategies of each step, in order to achieve the goal of mass production of efficient and reliable microfluidic water quality sensors.

[0078] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0079] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A water quality sensor based on MEMS microfluidics, characterized in that: The invention comprises a substrate, a microfluidic channel is arranged in the middle of the substrate, a detection component is arranged on one side of the microfluidic channel, and a heating electrode is arranged at the bottom of the microfluidic channel.

2. A MEMS microfluidic water quality sensor according to claim 1, characterized in that: The substrate comprises an upper layer, a middle layer and a lower layer, wherein the upper layer is a hydrophobic protective layer, the middle layer is an insulating medium layer, the lower layer is a base glass layer, and an electrode array layer is arranged on the base glass layer; metal tentacles are arranged at the bottom of the substrate, and the number of the metal tentacles is at least 1.

3. A MEMS microfluidic water quality sensor according to claim 2, characterized in that: The microfluidic channel is located in the silicon-based conductive layer.

4. A MEMS microfluidic water quality sensor according to claim 2, characterized in that: A heating electrode groove is etched on the base glass layer, the heating electrode is arranged in the heating electrode groove, and the heating electrode is in a serpentine shape.

5. A MEMS microfluidic water quality sensor according to claim 2, characterized in that: The insulating dielectric layer material is one of silicon oxide, silicon nitride or aluminum oxide, and the insulating dielectric layer thickness is 100-200nm; the hydrophobic protective layer material is polytetrafluoroethylene; and the silicon-based conductive layer material is indium tin oxide conductive glass.

6. The MEMS microfluidic water quality sensor according to claim 1, characterized in that: The detection component comprises a waveguide cavity, a light guide grid is arranged inside the waveguide cavity, and the number of the light guide grid is at least one group; an ultraviolet light source and a silicon photocell are arranged on one side of the waveguide cavity.

7. A MEMS microfluidic water quality sensor according to claim 6, characterized in that: The ultraviolet light source comprises an ultraviolet light emitting module, and the ultraviolet light emitting module is provided with a light emitting unit, and the number of the light emitting unit is at least one.

8. The MEMS microfluidic water quality sensor according to claim 7, characterized in that: The ultraviolet light emitting module adopts a mixture of two of gallium arsenide, cadmium sulfide, indium phosphide or zinc sulfide, and the wavelength of the light emitting unit is 365-405nm.

9. A MEMS microfluidic water quality sensor according to any one of claims 6-8, characterized in that: The light guide grid material is one of fused quartz, calcium fluoride, magnesium fluoride, ultraviolet fused amorphous silicon dioxide, germanium or zinc selenide; the light guide grid is arranged parallel to the substrate, and the ultraviolet light source passes through the waveguide cavity into the microfluidic channel.

10. A detection method based on MEMS microfluidic water quality sensor, characterized in that: The specific steps include: (i) Pretreatment: injecting a liquid sample into the microfluidic channel and heating the liquid sample by controlling the temperature using a heating electrode; (ii) Excitation light source: when performing electrical control, the ultraviolet light source at the location of the liquid to be detected is controlled to emit ultraviolet light of a preset band, which is guided by the waveguide cavity so that the ultraviolet light penetrates or irradiates the detection liquid, thereby exciting the target compound in the detection liquid to produce an optical response; (III) Collecting detection information: turning on the first ultraviolet light source, and controlling the heating electrodes around the position of the droplet to be detected, and closing them in sequence along the detection direction; further collecting the light reflected, scattered or fluorescent by the sample, and when turning on the second ultraviolet light source, turning off the first ultraviolet light source, controlling the heating electrodes around the position of the droplet to be detected, and closing them in sequence along the detection direction, recovering them through the waveguide cavity and the optical grid and guiding them to the silicon photocell; (IV) Information processing: Silicon photocells convert received optical signals into electrical signals, amplify and process the signals to identify and quantify specific components or properties in the sample; based on the intensity, waveform or other characteristic parameters of the electrical signal, combined with a preset calibration curve or algorithm, the component concentration, purity or specific physical and chemical parameters of the liquid to be tested are analyzed and obtained.

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