CN113091941A - Microfluidic temperature sensing module and temperature characterization method thereof - Google Patents
Microfluidic temperature sensing module and temperature characterization method thereof Download PDFInfo
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- CN113091941A CN113091941A CN202110340218.1A CN202110340218A CN113091941A CN 113091941 A CN113091941 A CN 113091941A CN 202110340218 A CN202110340218 A CN 202110340218A CN 113091941 A CN113091941 A CN 113091941A
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/34—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using capacitative elements
- G01K7/343—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using capacitative elements the dielectric constant of which is temperature dependant
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- G01K13/00—Thermometers specially adapted for specific purposes
- G01K13/02—Thermometers specially adapted for specific purposes for measuring temperature of moving fluids or granular materials capable of flow
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K15/00—Testing or calibrating of thermometers
- G01K15/005—Calibration
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- G—PHYSICS
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
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Abstract
The invention belongs to the field of electronic devices, and discloses a microfluidic temperature sensing module and a temperature characterization method thereof. The micro-fluidic temperature sensing module comprises a first layer of coplanar waveguide transmission line structure, a second layer of sealing plate film and a third layer of microfluidic chip, wherein a resonance unit is loaded on the coplanar waveguide transmission line structure, so that the band elimination function near the resonance frequency is realized. The microfluidic temperature sensing module disclosed by the invention is simple in structure, small in size, convenient to use and high in stability. The invention also discloses a temperature characterization method of the microfluidic temperature sensing module, and the corresponding temperature value can be directly searched through the tested frequency deviation more conveniently by a fitting method of a calibration line (a corresponding curve of the frequency deviation and the temperature) of the microfluidic temperature sensing module. In conclusion, the designed microfluidic temperature sensing module can not only realize accurate and stable sensing of temperature, but also has the advantages of simple structure, low cost, small size, easy integration, high environmental temperature and the like.
Description
Technical Field
The invention belongs to the field of electronic devices, and particularly relates to a microfluidic temperature sensing module and a temperature characterization method thereof.
Background
The temperature sensor refers to a sensor capable of sensing temperature and converting the sensed temperature into a usable output signal, and is a very popular and important sensor in sensors, and is generally divided into two categories: contact and contactless. The contact temperature sensor needs to keep thermal contact with a measured medium, and mainly comprises a resistance type, a thermocouple, a PN junction temperature sensor and the like. The non-contact temperature sensor does not need to be in contact with a measured medium, but measures temperature through heat radiation or convection of the measured medium, and mainly comprises an infrared temperature measurement sensor and the like.
With the development of the internet of things, new requirements for wireless sensing are provided for various sensors. The wireless sensor integrates the advantages of non-line-of-sight transmission, grid control, automatic management, low power consumption and the like of sensing and wireless communication technologies, and is the development direction of future sensing.
Microfluidic technology is the science and technology of systems that handle or manipulate small volumes of fluid, using microfluidic channels typically only tens to hundreds of microns in size. With the introduction of microfluidics, sensing and interface electronics, fluid manipulation structures and fluidic channels can be integrated on a single packaged chip, and fluidic analysis can be performed on samples on the order of microliters.
Disclosure of Invention
The invention aims to provide a microfluidic temperature sensing module and a temperature characterization method thereof, so as to realize the technical problem of accurately and stably sensing temperature by using a microfluidic channel.
In order to solve the technical problems, the specific technical scheme of the microfluidic temperature sensing module and the temperature characterization method thereof is as follows:
a microfluidic temperature sensing module comprises a first layer of coplanar waveguide transmission line structure, a second layer of sealing plate film and a third layer of microfluidic chip, wherein the first layer of coplanar waveguide transmission line structure comprises a coplanar waveguide transmission line grounding strip, a coplanar waveguide transmission line central strip, three grooves of the coplanar waveguide transmission line central strip and bending line resonance units loaded in the grooves, the third layer of microfluidic chip comprises a microfluidic chip substrate and three microfluidic channels, and the second layer of sealing plate film is adhered between the first layer of coplanar waveguide transmission line structure and the third layer of microfluidic chip.
Further, the resonance unit is composed of three meander-line resonators, and the lengths of the three meander-line resonators are increased progressively.
Furthermore, the three micro-flow channels correspond to the positions of the structural gaps of the three bending-line resonators in the first layer and are complementary with the structures of the bending-line resonance units.
Further, the microfluidic channel is filled with a liquid with a dielectric constant changing with temperature.
Further, the liquid may be a single liquid material or a mixed liquid material, preferably pure water, methanol, or a mixed liquid of the two.
Advantages of the temperature sensing module of the present invention include:
(1) the structure is simple: the module only comprises a coplanar waveguide structure and a microfluidic chip, other electronic devices and temperature sensing materials are not needed, and complicated wiring and processing are not needed;
(2) and (3) miniaturization: the module has small size and light weight, and is convenient to use in various environments and equipment;
(3) the use is convenient: the coplanar waveguide interface is convenient to be integrated with other modules or systems;
(4) the stability is high: simulation and test results of the module demonstrate a fixed correspondence between frequency offset and temperature, independent of the initial resonant frequency, which is heavily influenced by the environment. The frequency offset-temperature calibration curve of the module can be quantitatively analyzed through dielectric characteristics of liquid used in a microfluidic channel, is less influenced by the environment, and has higher stability compared with the conventional temperature sensor.
The invention also discloses a temperature characterization method of the microfluidic temperature sensing module, which comprises the following steps:
step 1: distilled water was chosen as the liquid in the microfluidic channel.
Step 2: the relative permittivity of water is given according to the debye relaxation model:
where ω is 2 π f, ε∞Is the dielectric function at infinite frequency, epsilonsIs the static dielectric constant and τ is the relaxation time.
For distilled water,. epsilon∞The static dielectric constant and relaxation time were obtained using third order regression fit as 4.9:
εs＝88.045-0.4147T+6.295×10-4T2+1.075×10-5T3
τ＝1.768×10-11-6.086×10-13T+1.104×10-14T2-8.111×10-17T3
calculating the dielectric constant of the distilled water at different temperatures;
and step 3: introducing the dielectric constant value into the simulation by utilizing simulation software;
and 4, step 4: and according to the simulation result, the conclusion that a corresponding mathematical relation exists between the frequency deviation and the temperature and the relation is not related to the initial resonant frequency seriously influenced by the environment is obtained.
The temperature characterization method of the microfluidic temperature sensing module has the following advantages: by the fitting method of the calibration line (the corresponding curve of the frequency deviation and the temperature) of the microfluidic temperature sensing module, the corresponding temperature value can be directly searched through the tested frequency deviation more conveniently. The sensing module has simple structure, low cost and convenient processing; the size is small, the weight is light, the coplanar waveguide interface is convenient to be integrated with other modules or systems, and the coplanar waveguide interface is convenient to use in various environments and equipment; the frequency offset-temperature calibration curve of the module can be quantitatively analyzed through dielectric characteristics of liquid used in a microfluidic channel, is less influenced by the environment, and has higher stability compared with the conventional temperature sensor.
In conclusion, the micro-fluidic temperature sensing module designed by the invention can realize accurate and stable sensing of temperature, and has the advantages of simple structure, low cost, small size, easy integration, high environmental temperature property and the like, so that the micro-fluidic temperature sensing module has wide application value and market potential.
Drawings
Fig. 1 is a top view of a first layer structure of a microfluidic temperature sensing module.
Fig. 2 is a top view of a second layer structure of the microfluidic temperature sensing module.
Fig. 3 is a top view of a third layer structure of the micro-fluidic temperature sensing module.
Fig. 4 is a graph of frequency simulation and test results of the microfluidic temperature sensing module.
Fig. 5 is a graph of calibration line fit results for a microfluidic temperature sensing module.
The notation in the figure is: 1. a coplanar waveguide transmission line structure; 3. a microfluidic chip; 1-1, a coplanar waveguide transmission line grounding strip; 1-2, a coplanar waveguide transmission line central strip; 1-3, slotting; 1-4, a meander line resonant cell; 2-1, sealing the plate film; 3-1, microfluidic chip substrate; 3-2, microfluidic channels.
Detailed Description
In order to better understand the purpose, structure and function of the present invention, a microfluidic temperature sensing module and a temperature characterization method thereof according to the present invention are further described in detail below with reference to the accompanying drawings.
As shown in fig. 1 to 3, the microfluidic temperature sensing module of the present invention includes a first coplanar waveguide transmission line structure 1, a second package film 2-1, and a third microfluidic chip 3.
As shown in fig. 1, the first layer of coplanar waveguide transmission line structure includes a coplanar waveguide transmission line grounding strip 1-1, a coplanar waveguide transmission line central strip 1-2, three slots 1-3 of the coplanar waveguide transmission line central strip 1-2, and meander line resonant units 1-4 loaded in the slots 1-3, wherein the resonant units 1-4 are composed of three meander line resonators, and the lengths of the three meander line resonators are increased progressively. Due to the existence of the meander line resonant unit 1-4, the energy at the resonant frequency corresponding to the meander line resonant unit 1-4 in the output signal of the coplanar waveguide transmission line that normally transmits electromagnetic waves is consumed by the meander line resonator, which is reflected in the test result that three troughs appear in S12 of the coplanar waveguide transmission line.
As shown in fig. 2, a second layer of package film 2-1 of the microfluidic temperature sensing module is used as a substrate of the first layer of coplanar waveguide transmission line structure 1 and a package film of the third layer of microfluidic chip 3, and plays a role in adhering the upper and lower layer structures and sealing the lower layer of microfluidic chip 3.
As shown in fig. 3, the third layer of the microfluidic chip 3 of the microfluidic temperature sensing module is composed of a microfluidic chip substrate 3-1 and three microfluidic channels 3-2. The microfluidic channel 3-2 is filled with a liquid having a dielectric constant varying with temperature, and the liquid may be a single liquid material or a mixed liquid material, such as pure water, methanol, or a mixture thereof. The three micro-flow channels 3-2 correspond to the positions of the structural gaps of the three bending-line resonators in the first layer and are complementary to the structures of the bending-line resonance units 1-4, so that the dielectric constant of the injected liquid in the micro-flow channels 3-2 can also influence the resonance frequency of the bending-line resonance units 1-4. The frequency of the three wave troughs in S12, which is the coplanar waveguide transmission line in the test results, varies with the type and temperature of the injected liquid in the microfluidic channel 3-2.
Fig. 4 is a diagram of the simulation and test results of S12 of the micro-fluidic temperature sensing module of the present invention. As shown in fig. 4, the simulation result of S12 has a frequency deviation from the actual measurement result. The main reasons for this are variations in the dielectric constant of different batches of substrate materials and environmental disturbances that are difficult to avoid. Therefore, if the temperature is characterized by the resonant frequency, additional error is inevitably introduced into the frequency-temperature mapping relationship. In order to solve the error problem, the deviation of the frequency along with the temperature change is selected as an index for representing the temperature, and the environmental stability of the index is proved through theoretical analysis.
In the case of pure water, distilled water is selected as the liquid in the microfluidic channel 3-2 in the sensor module of the present invention. The relative permittivity of water is given according to the debye relaxation model:
where ω is 2 π f, ε∞Is the dielectric function at infinite frequency, epsilonsIs the static dielectric constant, and τ is the relaxation timeAnd (3) removing the solvent.
For distilled water,. epsilon∞The static dielectric constant and relaxation time can be obtained with a third order regression fit as 4.9:
εs＝88.045-0.4147T+6.295×10-4T2+1.075×10-5T3
τ＝1.768×10-11-6.086×10-13T+1.104×10-14T2-8.111×10-17T3
the dielectric constant of distilled water at different temperatures can be calculated by the above formula. The dielectric constant values are then introduced into the simulation using simulation software. Fig. 5 shows the simulation result of the frequency deviation of different resonant elements after injecting distilled water into the corresponding channels. The results show that there is a corresponding mathematical relationship between frequency shift and temperature that is independent of the initial resonant frequency, which is severely affected by the environment. This result demonstrates that temperature can be characterized by a corresponding frequency offset, and that the characterization is ambient temperature.
Also shown in fig. 5 is a frequency offset versus temperature fit curve showing the fourth order temperature dependence of the frequency offset. This curve is the calibration curve of the proposed sensing module and can be used to find the corresponding temperature value directly from the measured frequency offset (it is only applicable when the liquid in the microfluidic channel 3-2 is distilled water, and it can be re-fitted by the above process when other liquids are used instead).
It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (6)
1. A micro-fluidic temperature sensing module comprises a first coplanar waveguide transmission line structure (1), a second sealing plate film (2-1) and a third micro-fluidic chip (3), the micro-fluidic chip is characterized in that the first layer of coplanar waveguide transmission line structure (1) comprises a coplanar waveguide transmission line grounding strip (1-1), a coplanar waveguide transmission line central strip (1-2), three grooves (1-3) of the coplanar waveguide transmission line central strip (1-2) and bending line resonance units (1-4) loaded in the grooves (1-3), the third layer of micro-fluidic chip (3) comprises a micro-fluidic chip substrate (3-1) and three micro-fluidic channels (3-2), and the second layer of sealing plate film (2-1) is adhered between the first layer of coplanar waveguide transmission line structure (1) and the third layer of micro-fluidic chip (3).
2. Microfluidic temperature sensing module according to claim 1, characterized in that the resonance unit (1-4) consists of three meander-line resonators, the length of which increases.
3. Microfluidic temperature sensing module according to claim 2, wherein the three microfluidic channels (3-2) are exactly corresponding to the positions of the structural slits of the three meander-line resonators in the first layer, complementary to the structure of the meander-line resonant cells (1-4).
4. Microfluidic temperature sensing module according to claim 3, wherein the microfluidic channel (3-2) is filled with a liquid having a dielectric constant that varies with temperature.
5. The microfluidic temperature sensing module according to claim 4, wherein the liquid can be a single liquid material or a mixed liquid material, preferably pure water, methanol or a mixture of both.
6. A method for temperature characterization of a microfluidic temperature sensing module according to any of claims 1-5, comprising the steps of:
step 1: selecting distilled water as the liquid in the microfluidic channel (3-2);
step 2: the relative permittivity of water is given according to the debye relaxation model:
where ω is 2 π f, ε∞Is the dielectric function at infinite frequency, epsilonsIs the static dielectric constant, τ is the relaxation time;
for distilled water,. epsilon∞The static dielectric constant and relaxation time were obtained using third order regression fit as 4.9:
εs＝88.045-0.4147T+6.295×10-4T2+1.075×10-5T3
τ＝1.768×10-11-6.086×10-13T+1.104×10-14T2-8.111×10-17T3
calculating the dielectric constant of the distilled water at different temperatures according to the formula;
and step 3: introducing the dielectric constant value into the simulation by utilizing simulation software;
and 4, step 4: and according to the simulation result, the conclusion that a corresponding mathematical relation exists between the frequency deviation and the temperature and the relation is not related to the initial resonant frequency seriously influenced by the environment is obtained.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113959564A (en) * | 2021-09-17 | 2022-01-21 | 杭州电子科技大学 | Temperature compensated microstrip sensor for microfluidics |
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