Electrophoretic separation test method for detecting multiple solutes in solution
By combining electrophoretic separation with terahertz metasurface sensors and porous hydrogels, the problems of solute concentration differentiation and sample contamination in solution detection by terahertz metasurface sensors are solved, enabling rapid separation and efficient detection of multi-solute solutions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING INSTITUTE OF TECHNOLOGY (ZHUHAI)
- Filing Date
- 2026-01-16
- Publication Date
- 2026-04-10
AI Technical Summary
Existing terahertz metasurface sensors have difficulty distinguishing solute concentrations in solution sensing and detection. Solution detection is subject to problems such as sample contamination and time and labor costs, especially when separating and detecting multiple solutes, resulting in low efficiency.
An electrophoretic separation method combined with a terahertz metasurface sensor and a porous hydrogel was adopted. The rapid separation and detection of multiple solutes in the solution was achieved by using a microfluidic chip. Electrophoresis was applied to both ends of the porous hydrogel using a bias voltage. The hydrogel was then dried in a constant temperature drying oven to precipitate the solutes. Finally, a terahertz time-domain spectrometer was used for sensing and testing.
It enables rapid separation and efficient detection of multi-solute solutions, solves the problem of difficulty in distinguishing solute concentrations in solution sensing detection, avoids sample contamination and time-consuming and labor-intensive processes, and improves the efficiency of solute separation and detection.
Smart Images
Figure CN121830561A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of terahertz metasurface sensing, in particular to an electrophoretic separation test method for detecting multiple solutes in a solution. BACKGROUND
[0002] Terahertz waves are electromagnetic waves with a wavelength between microwaves and infrared and a frequency of 100GHz to 10THz. In the past 20 years, terahertz waves have received extensive attention and research due to their high penetration, wide band, and low photon energy. The terahertz spectrum of a substance is often analyzed using a terahertz time-domain spectrometer to obtain vibration and rotation information of the molecules of the substance under a wide frequency spectrum. However, the resolution of the terahertz time-domain spectrometer is limited, and its sensitivity is insufficient to detect the differences in the spectral properties of trace samples. In order to meet the sensing and detection of trace samples, the intensity of the terahertz wave needs to be locally enhanced to reduce the demand for sample quantity. A magnetic metasurface is composed of periodically arranged sub-wavelength unit cells. The unique response of the metasurface to electromagnetic waves is determined by the geometric configuration of the unit cell structure, and we can optimize the structure shape to design different response resonance characteristic peaks. Using such a material that is sensitive to changes in the local electric field environment as a sensor in combination with a terahertz time-domain spectrometer can greatly improve the detection sensitivity and eliminate the need for sample labeling. This method has great value for biomedical and chemical analysis.
[0003] Terahertz band metasurface sensors have achieved good sensing sensitivity and testing stability in solid powder testing and biochemical tissue culture testing, but it is still difficult to achieve in solution sensing detection. The reason is that due to the influence of the solution environment, the chemical bond disturbance frequency of water molecules is in the terahertz band, and water solution has a high absorption of terahertz waves. Under the premise of solution testing, it is difficult to distinguish the concentration of solutes, and it is difficult to accurately sense. The existing technology uses a drying method for liquid detection. This method is prone to sample contamination during drying, and additional steps are required for the separation of multiple solutes in the solution. Separation of the solution before detection also requires additional time, which causes technical problems such as sample contamination and time-consuming and labor-intensive.
[0004] Therefore, how to avoid the interference of water in the solution and more quickly separate and detect multiple solutes in the solution is an important step in promoting the application and marketization of terahertz metasurface sensors. SUMMARY
[0005] The purpose of the embodiments of the present application is to provide a method for detecting multiple solutes in a solution based on a terahertz super surface, which not only solves the technical problems that it is difficult to distinguish the concentration of solutes and it is impossible to accurately sense in the prior art solution sensing and detection, but also solves the technical problems of sample pollution and time-consuming and laborious, so as to improve the solute separation efficiency of the multi-solute solution and improve the solute detection efficiency.
[0006] In order to achieve the above-mentioned purpose, the present application provides an electrophoresis separation test method for detecting multiple solutes in a solution, characterized by comprising the following steps S1. Preparing a microfluidic chip: first, using a drawing software to obtain the layout of the microfluidic chip, then using a 3D printing technology to obtain the microfluidic chip for standby; S2. Preparing a terahertz super surface sensor: using a photoetching technology to form a designed super surface pattern on a substrate to obtain a terahertz super surface sensor for standby; S3. Preparing a porous hydrogel: taking the hydrogel and pouring it into a mold to form a layered precursor, then low-temperature freezing the layered precursor to crystallize the water in the solution, and finally low-temperature thawing to obtain a porous hydrogel for standby; S4. Solute separation by electrophoresis: placing the terahertz super surface sensor in step S2 and the porous hydrogel in step S3 in the microfluidic chip in step S1, then taking the mixed solution to be detected and dropping it into the groove of the porous hydrogel, and fixing the microfluidic chip; applying a bias voltage to the electrode assembly at both ends of the porous hydrogel for a first preset time of electrophoresis; S5. Sensing and detection: placing the microfluidic chip with the terahertz super surface sensor and the porous hydrogel into a constant temperature drying oven, and continuously drying at a preset temperature for a second preset time, until the multiple solutes are appropriately precipitated at the combination of the porous hydrogel and the terahertz super surface sensor; then using a terahertz time domain spectrometer to sequentially perform sensing test on the point of precipitated solute.
[0007] Based on the first aspect, in the embodiments of the present application, in step S5, the bias voltage is specifically set as a pressure difference of 30-50V; and the first preset time of electrophoresis is 8-12min.
[0008] Based on the first aspect, in the embodiments of the present application, in step S6, the drying temperature of the constant temperature drying oven is set to 30-50℃; and the second preset time of drying is 8-12min.
[0009] Based on the first aspect, in the embodiments of the present application, the step S1 of preparing a microfluidic chip comprises the following sub-steps: S11. Using a SolidWorks or UG drawing software to sequentially obtain the model of a first insulating mounting frame, a second insulating mounting frame, a first limiting plate, a second limiting plate, a group of fences and a group of electrodes; S12. Convert the model diagrams in step S11 into STL or OBJ format diagrams in sequence; S13. Import the format diagram from step S12 into slicing software: Cura or Simplify3D, then adjust the position and set the size and fill parameters to generate G-code; S14. Transfer the G code from step S13 to the 3D printer via USB, SD card, or Wi-Fi; S15. On the 3D printer's control panel, select the G-code file uploaded in step S14, and click Start Printing. This will produce a structural product consisting of a first insulating mounting bracket, a second insulating mounting bracket, a first limiting plate, a second limiting plate, a set of enclosures, and a set of electrodes. S16. Place the second limiting plate on the second insulating mounting bracket, then place the enclosure and electrode on the upper surface of the second limiting plate. The enclosure and electrode form a groove for placing the terahertz metasurface sensor and the porous hydrogel. Next, place the first limiting plate on the upper surface of the enclosure and electrode. Finally, place the second insulating mounting bracket on the upper surface of the first limiting plate and fix the first and second insulating mounting brackets with bolts to obtain the microfluidic chip.
[0010] Based on the first aspect, in the embodiments of this application, in step S15 above, the 3D printer uses TPX (4-methyl-1-pentene) as raw material when printing the first limiting plate and the second limiting plate.
[0011] Based on the first aspect, in the embodiments of this application, in step S15 above, the 3D printer uses any one of the following raw materials when printing the first insulating fixing frame and the second insulating mounting frame: PLA (polylactic acid), ABS (acrylonitrile-butadiene-styrene copolymer), PETG (polyethylene terephthalate-1,4-cyclohexanediol ester), and PEI (polyetherimide). Based on the first aspect, in the embodiments of this application, in step S15 above, the 3D printer uses any one of the following raw materials when printing electrodes: pure copper, chromium zirconium copper alloy, GRCop alloy, and copper-nickel alloy.
[0012] Based on the first aspect, in the embodiments of this application, step S2, which involves fabricating a terahertz metasurface sensor, includes the following sub-steps: S21. Design metasurface structure patterns using electromagnetic simulation software (CST); S22. After ultrasonically cleaning the substrate with acetone or isopropanol to remove impurities, dry it for later use. S23. Take the substrate from step 22 and coat the substrate surface with photoresist; then cover the transparent substrate with the metasurface structure pattern from step S21 onto the photoresist, and then form the photoresist pattern of the metasurface structure on the substrate through ultraviolet light exposure and development process. S24. A metal thin film is deposited on the substrate surface of the photoresist pattern formed in step S23 by electron beam evaporation. Then, an etching process is used to remove the metal parts that are not protected by the photoresist to form a metal metasurface structure. Finally, the photoresist is removed to obtain the terahertz metasurface sensor.
[0013] Based on the first aspect, in the embodiments of this application, the substrate in step S22 is prepared from any one of the following materials: fused silica, borosilicate glass, or sapphire.
[0014] Based on the first aspect, in the embodiments of this application, the preparation of porous hydrogel in step S3 includes the following sub-steps: S31: Select gelatin and / or polyvinyl alcohol, dissolve them in water, stir evenly to prepare a solution of a certain concentration, and set aside for later use; S32: The solution prepared in step S31 is used to prepare a mixed solution containing bubbles using the modified Tessari method, for later use; S33: Transfer the mixed solution containing air bubbles from step S32 into a mold to form a layered precursor. Then, place the layered precursor in a refrigerator and freeze it for a certain period of time to allow the solvent water to crystallize into ice crystals, forming a porous layered structure for later use. S34: Place the porous layered structure from step S33 into a freeze dryer for freeze drying, and then soak it in TBE buffer solution to obtain a porous hydrogel with a bubble structure.
[0015] The solution provided in this application has at least the following beneficial effects: This solution is a novel method for detecting multi-solute mixed solutions, breaking through the existing limitations of terahertz sensing in detecting multi-solute solutions. It achieves rapid separation of multiple solutes through electrophoresis, and subsequent drying avoids direct detection of the solvent portion. It not only solves the technical problems of existing solution sensing methods, such as difficulty in distinguishing solute concentrations and inaccurate sensing, but also solves the problems of sample contamination and time-consuming and labor-intensive processes. It significantly improves the solute separation efficiency of multi-solute solutions and enhances solute detection efficiency. At the same time, compared with traditional methods that separate first and then detect, this method is faster and simpler in concentration testing. The microfluidic chip required by this method is also very inexpensive and easy to prepare.
[0016] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description
[0017] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings: Fig. 1 The flowchart of the method for detecting multiple solutes in solution based on terahertz metasurface sensing in this embodiment is illustrated schematically. Fig. 2 The schematic diagram illustrates the operation of the method for detecting multiple solutes in solution based on terahertz metasurface sensing in this embodiment.
[0018] Explanation of reference numerals in the attached drawings: First insulating mounting bracket 01, First limiting plate 02, Enclosure 03, Electrode 04, Second limiting plate 05, Second insulating mounting bracket 06, Limiting boss 07, Terahertz metasurface sensor 08, Porous hydrogel 09, Sample cell 10, Placement cell 11, Solute 12. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0020] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.
[0021] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.
[0022] like Figs. 1-2As shown, this embodiment provides an electrophoretic separation test method for detecting multiple solutes in a solution, including the following steps: S1. Fabrication of microfluidic chips: First, the microfluidic chip pattern is obtained using drawing software, and then the microfluidic chip is obtained using 3D printing technology for later use; S2. Fabrication of terahertz metasurface sensor 08: After forming the designed metasurface pattern on the substrate using photolithography, terahertz metasurface sensor 08 is obtained for later use; S3. Preparation of porous hydrogel 09: Pour the hydrogel into a mold to form a layered precursor, then freeze the layered precursor at low temperature to crystallize the water in the solution, and finally thaw at low temperature to obtain porous hydrogel 09 for later use. S4. Electrophoretic solute separation: Take the terahertz metasurface sensor 08 from step S2 and the porous hydrogel 09 from step S3 and place them in the microfluidic chip from step S1. Then, take the mixed solution to be detected and drop it into the groove of the porous hydrogel 09. After fixing the microfluidic chip, apply a bias voltage to the electrode 04 components at both ends of the porous hydrogel 09 and continue electrophoresis for a first preset time. S5. Sensing and Detection: The microfluidic chip with terahertz metasurface sensor 08 and porous hydrogel 09 is placed in a constant temperature drying oven and dried continuously at a preset temperature for a second preset time until a suitable amount of various solutes are precipitated at the junction of porous hydrogel 09 and terahertz metasurface sensor 08; then, the precipitated solutes are sequentially sensed and tested using a terahertz time-domain spectrometer.
[0023] This embodiment enables rapid separation and detection of complex samples via electrophoresis. Specifically, a microfluidic chip, a terahertz metasurface sensor 08, and a porous hydrogel 09 are first prepared. Then, the terahertz metasurface sensor 08 and the porous hydrogel 09 are placed inside the microfluidic chip for electrophoresis. After electrophoresis, the encapsulation cover and electrode 04 assembly are removed, and the chip is dried in a constant-temperature drying oven. The multi-solute solution can then be separated, and a suitable amount of precipitate appears at the junction of the hydrogel layer and the terahertz metasurface sensor. This structure not only enables sensing and detection of multi-solute solutions, solving the technical problems of difficulty in distinguishing solute concentrations and inaccurate sensing in existing solutions, but also solves the problems of sample contamination and time-consuming processes. It significantly improves the solute separation efficiency and detection efficiency of multi-solute solutions.
[0024] The principle behind solute separation in the mixed solution during the electrophoresis process described above is as follows: Different solute molecules have different molecular masses and charge characteristics. Substances with larger molecular masses pass through the pores of the hydrogel more slowly than those with smaller molecular masses under the same bias voltage. Different substances possess different charge characteristics, and under the influence of the voltage across the two sides, the substances will also move to either side according to their own charge characteristics. Through the combined effect of these two factors, substances with different molecular masses and charge characteristics can be separated.
[0025] In a preferred embodiment, in step S5, applying the bias voltage specifically involves setting the voltage difference between the two sides to 30-50V and the first preset electrophoresis time to 8-12 minutes.
[0026] In a preferred embodiment, in step S6, the drying temperature of the constant temperature drying oven is set to 30-50℃; the second preset drying time is 8-12 minutes.
[0027] Furthermore, the porous hydrogel 09 has a length of 30-50 mm, a width of 30-50 mm, and a thickness of 2-3 mm; Furthermore, the porous hydrogel 09 has a sample groove for containing the target solution; the sample groove has a length of 3-7 mm, a width of 3-7 mm, and a height of 1-2 mm; Furthermore, the terahertz metasurface sensor has a length of 30-50 mm, a width of 30-50 mm, and a thickness of 450-550 μm.
[0028] Furthermore, the microfluidic chip, from top to bottom, includes: a first insulating mounting bracket 01, a first limiting plate 02, a set of enclosures 03, a set of electrodes 04, a second limiting plate 05, and a second insulating mounting bracket 06; the second insulating mounting bracket 06 has a limiting boss 07 on one side relative to the first insulating mounting bracket 01; the first insulating mounting bracket 01 is connected to the limiting boss 07 of the second insulating mounting bracket 06 by a fixing member, and a placement cavity is formed between the first insulating mounting bracket 01 and the first insulating mounting bracket 06; the second limiting plate 05 is placed on the upper surface of the second insulating mounting bracket 06, and a set of electrodes 04 is disposed on the upper surface of the second limiting plate 05, with the other end of the electrode 04 assembly extending to the second insulating mounting bracket 06. Externally; a set of enclosures 03 are disposed between the two electrodes 04, forming a placement groove 11 with the set of electrodes 04; specifically, when solution detection is required, the terahertz metasurface sensor is first placed in the placement groove, and then the porous hydrogel 09 is placed on the surface 08 of the terahertz metasurface sensor, so that the two are in contact with each other. At the same time, the two sides of the porous hydrogel 09 should be in contact with the electrodes 04. Next, the solution to be tested is added into the sample groove on the surface of the porous hydrogel 09, and then the first limiting plate 02 is placed on the surface of the porous hydrogel 09 layer. Finally, the first insulating mounting bracket 01 is placed on the surface of the first limiting plate 02, and the first insulating mounting bracket 01 and the second insulating mounting bracket 06 are sealed and fixed by bolts.
[0029] Specifically, in the aforementioned microfluidic chip, the length of the first insulating mounting bracket 01 is 50-70mm and the width is 50-70mm; the height of the limiting boss 07 of the second insulating mounting bracket 06 is 8-12mm; the length and width of the second insulating mounting bracket 06 are the same as those of the first insulating mounting bracket 01. The transverse cross-section of each electrode 04 is T-shaped; the length of each electrode 04 is 30-50mm, the width is 8-12mm, and the thickness is 2-4mm. The first limiting plate 02 has a length of 40-60mm, a width of 40-60mm, and a height of 3-4mm; the second limiting plate 05 has the same length, height, and width as the first limiting plate 02. The length of the 03 panel of the enclosure is 40-60mm, the width is 5-12mm, and the height is 2.5-3.5mm.
[0030] In a preferred embodiment, step S1, which involves fabricating a microfluidic chip, includes the following sub-steps: S11. Use SolidWorks or UG drawing software to obtain the model drawings of the first insulating mounting bracket 01, the second insulating mounting bracket 06, the first limiting plate 02, the second limiting plate 05, a set of enclosures 03 and a set of electrodes 04 in sequence. S12. Convert the model diagrams in step S11 into STL or OBJ format diagrams in sequence; S13. Import the format diagram from step S12 into slicing software: Cura or Simplify3D, then adjust the position and set the size and fill parameters to generate G-code; S14. Transfer the G code from step S13 to the 3D printer via USB, SD card, or Wi-Fi; S15. On the 3D printer's control panel, select the G-code file uploaded in step S14, and click Start Printing. This will produce a structural product consisting of a first insulating mounting bracket 01, a second insulating mounting bracket 06, a first limiting plate 02, a second limiting plate 05, a set of enclosures 03, and a set of electrodes 04. S16. Place the second limiting plate 05 on the second insulating mounting bracket 06, then place the enclosure 03 and electrode 04 on the upper surface of the second limiting plate 05. The enclosure 03 and electrode 04 form a groove 11 for placing the terahertz metasurface sensor 08 and the porous hydrogel 09. Next, place the first limiting plate 02 on the upper surface of the enclosure 03 and electrode 04. Finally, place the second insulating mounting bracket 06 on the upper surface of the first limiting plate 02, and then fix the first insulating mounting bracket 01 and the second insulating mounting bracket 06 with bolts to obtain the microfluidic chip.
[0031] In a preferred embodiment, in step S15 above, the 3D printer uses TPX (4-methyl-1-pentene) as raw material when printing the first limiting plate 02 and the second limiting plate 05.
[0032] In a preferred embodiment, in step S15 above, the 3D printer uses any one of the following raw materials when printing the first insulating mounting frame 01 and the second insulating mounting frame 06: PLA (polylactic acid), ABS (acrylonitrile-butadiene-styrene copolymer), PETG (polyethylene terephthalate-1,4-cyclohexanediol ester), and PEI (polyetherimide). In a preferred embodiment, in step S15 above, the 3D printer uses any one of the following raw materials when printing electrode 04: pure copper, chromium zirconium copper alloy, GRCop alloy, and copper-nickel alloy.
[0033] In a preferred embodiment, step S2, which involves fabricating the terahertz metasurface sensor 08, includes the following sub-steps: S21. Design metasurface structure patterns using electromagnetic simulation software (CST); the requirements for CST are as follows: CST frequency domain solver, frequency range 0.5-1.5THz, construct a 10×10SRR array (800μm×800μm); performance indicators: transmittance valley at 1THz ≤5%, Q value ≥50; output GDSII format pattern file for photolithography.
[0034] S22. After ultrasonically cleaning the substrate with acetone or isopropanol to remove impurities, dry it for later use; the substrate is selected as fused silica (εr≈3.8); acetone (≥99.5%), isopropanol (≥99.7%), deionized water (≥18.2MΩ·cm); equipment: dual-frequency ultrasonic cleaner (300-500W), vacuum drying oven (≤10Pa); S23. Take the substrate from step 22 and coat the substrate surface with photoresist; then cover the transparent substrate with the metasurface structure pattern from step S21 onto the photoresist, and then form the photoresist pattern of the metasurface structure on the substrate through ultraviolet light exposure and development process; wherein, photoresist: AZ5214E (1-3μm thick, resolution 1μm); mask: chrome-plated quartz plate (alignment accuracy ±0.5μm); equipment: spin coater, ultraviolet exposure machine (365nm), constant temperature development tank.
[0035] S24. A metal thin film is deposited on the substrate surface of the photoresist pattern forming the metasurface structure in step S23 by electron beam evaporation. Then, an etching process is used to remove the metal parts not protected by the photoresist to form a metal metasurface structure. Finally, the photoresist is removed to obtain the terahertz metasurface sensor 08. Among them, the target material is gold target (99.999%) and chromium target (99.99%); the etching solution is potassium iodide: iodine: water = 5:1:10 (mass ratio); the equipment is electron beam evaporator, wet etching tank, and plasma resist remover.
[0036] In a preferred embodiment, the substrate in step S22 is prepared from any one of fused silica, borosilicate glass, or sapphire; wherein, fused silica has extremely low absorption loss and very high transmittance in the terahertz band (typically 0.1 THz to 10 THz). Its absorption coefficient is very small in the terahertz range, allowing terahertz waves to effectively penetrate the substrate, thereby enabling sensor structures (such as antennas and resonators) to interact efficiently with terahertz waves.
[0037] In a preferred embodiment, step S3, preparing porous hydrogel 09, includes the following sub-steps: S31: Select gelatin and / or polyvinyl alcohol and dissolve them in water, stirring until a solution of a certain concentration is prepared and set aside. Specifically, gelatin dissolution requires heating (usually 50-60℃), but the temperature should not be too high (>70℃ will cause gelatin denaturation, affecting gel strength); polyvinyl alcohol needs to be heated and stirred (80-90℃) until completely dissolved to avoid residual particles causing uneven bubble distribution. The solution concentration needs to be controlled (usually 5%-15% gelatin concentration and 8%-12% polyvinyl alcohol concentration): too low a concentration will result in a weak gel skeleton, which is prone to collapse after freeze-drying; too high a concentration will result in too high a solution viscosity, making it difficult to introduce uniform bubbles.
[0038] S32: Using a modified Tessari method, prepare a mixed solution containing air bubbles from the solution prepared in step S31, and set it aside. Specifically, the shear rate or gas pressure needs to be controlled: too slow a rate will result in excessively large bubbles that are prone to bursting; too fast a rate will result in overly dense bubbles that are prone to merging during subsequent freezing, affecting the uniformity of pores. After the bubbles are introduced, they need to be quickly transferred to the mold (avoid prolonged placement, which may cause the bubbles to float or burst, resulting in reduced pores in the upper layer and denser pores in the lower layer).
[0039] S33: Transfer the mixed solution containing air bubbles from step S32 into a mold to form a layered precursor. Then, place the layered precursor in a refrigerator and freeze for a certain period of time to allow the solvent water to crystallize into ice crystals, forming a porous layered structure for later use. Specifically, the freezing temperature should be below 0°C (usually -18°C refrigerator, freezing time 4-8 hours): ensure that the water is completely crystallized and avoid some water not freezing, which would form a non-porous area after subsequent freeze-drying. The freezing time should not be too long (>12 hours may cause excessive growth of ice crystals, compressing the polymer skeleton and deforming the pores).
[0040] The mold should be made of a material with good thermal conductivity (such as polytetrafluoroethylene mold) to ensure uniform temperature during freezing and avoid excessive differences in the size of local ice crystals, which would result in an uneven layered structure.
[0041] S34: Place the porous layered structure from step S33 into a freeze dryer for freeze drying, and then soak it in TBE buffer solution to obtain a porous hydrogel 09 with a bubble structure. Specifically, the freezing process requires controlling the heating rate (slow heating, usually 5-10°C per hour): avoid heating too quickly to prevent ice crystals from melting and damaging the porous structure; the freeze-drying endpoint must ensure that the moisture content is <5% (too much residual moisture will cause the hydrogel to easily mold and affect storage stability).
[0042] The TBE buffer soaking time needs to be sufficient (usually 2-4 hours): to ensure that the porous framework is completely rehydrated (judgment criteria: the hydrogel volume recovers to 1.5-2 times that before lyophilization, and there are no dry and hard areas). After soaking, excess buffer solution on the surface needs to be removed to avoid residual liquid affecting subsequent use.
[0043] Example 1 like Fig. 2 As shown in this embodiment, an electrophoretic separation test method for detecting multiple solutes in a solution includes the following steps: Step 1: A microfluidic chip is fabricated. The microfluidic chip, from top to bottom, comprises: a first insulating mounting frame 01, a first limiting plate 02, a set of barriers 03, a set of electrodes 04, a second limiting plate 05, and a second insulating mounting frame 06. The first insulating mounting frame 01 has a length of 60mm and a width of 60mm. The length and width of the second insulating mounting frame 06 are the same as those of the first insulating mounting frame 01. The electrodes 04 have a T-shaped cross-section and a length of 40mm, a width of 10mm, and a thickness of 3mm. The first limiting plate 02 has a length of 50mm, a width of 50mm, and a height of 3.5mm. The length, height, and width of the second limiting plate 05 are the same as those of the first limiting plate 02. The barriers 03 have a length of 50mm, a width of 10mm, and a height of 3mm. Step 2: Prepare terahertz metasurface sensor 08; wherein, the terahertz metasurface sensor 08 has a length of 40 mm, a width of 40 mm, and a thickness of 500 μm; Step 3: Prepare a porous hydrogel 09; the porous hydrogel 09 has a length of 40 mm, a width of 40 mm, and a thickness of 2.5 mm; a sample groove 10 for containing the target solution is formed on the porous hydrogel 09; the sample groove 10 has a length of 5 mm, a width of 5 mm, and a height of 1.5 mm; Step 4: First, place the second limiting plate 05 into the limiting boss 0707 on the upper surface of the second insulating mounting bracket 06; then, place a set of enclosures 03 and a set of electrodes 04 on the upper surface of the second limiting plate 05 to form a placement groove 11; next, place the terahertz metasurface sensor 08 into the placement groove 11, and then place the porous hydrogel 09 on the upper surface of the terahertz metasurface sensor 08. Requirements: the bottom surface of the porous hydrogel 09 must be completely in contact with the upper surface of the terahertz metasurface sensor 08, and both ends of the porous hydrogel 09 must be completely in contact with a set of electrodes 04; then, drop the mixed solution to be tested into the sample groove 10 of the porous hydrogel 09; next, place the first limiting plate 02 on the upper surface of the porous hydrogel 09; finally, place the first insulating mounting bracket 01 on the surface of the first limiting plate 02, and encapsulate and fix the first insulating mounting bracket 01 and the second insulating mounting bracket 06 with bolts.
[0044] S4. Apply a bias voltage to the electrode 04 assembly at both ends of the porous hydrogel 09 and perform electrophoresis for a first preset time, wherein the voltage difference between the two sides is set to 40V; the first preset time for electrophoresis is 10min. S5. Sensing and Detection: First, loosen the bolts between the first insulating mounting bracket 01 and the second insulating mounting bracket 06, and remove the first insulating mounting bracket 01; then place the remaining structural parts in a constant temperature drying oven and continue drying at a preset temperature for a second preset time until a suitable amount of various solutes 12 precipitate at the junction of the porous hydrogel 09 and the terahertz metasurface sensor 08; wherein, the drying temperature of the constant temperature drying oven is set to 40℃; and the second preset drying time is 10min. S6. Position the terahertz metasurface sensor 08 according to the position of the central spot of the terahertz time-domain spectrometer, and perform sensing tests on the points where the precipitated solute 12 is deposited in sequence.
[0045] The principle of this method for rapid solute separation is the same as that of electrophoresis, but it requires less time compared to conventional electrophoresis. This is because the resolution of a terahertz time-domain spectrometer can reach 1 mm, and the periodic structure of a terahertz metasurface sensor is only about 100 μm. As long as the separation distance between the two substances exceeds 1 mm, only one substance will exist within the spectrometer's detection point, and at least one periodic metasurface structure will enhance the terahertz light. Therefore, the voltage can be appropriately set according to the molecular weight of the analyte to further accelerate the testing speed. This method also has higher efficiency than solid-phase extraction and liquid-phase extraction techniques. These two common extraction techniques require selecting multiple extraction columns based on the various physicochemical properties of the substances to separate each substance sequentially, and each pass through an extraction column also requires a certain amount of time (generally more than 5 minutes per column). The entire extraction process requires conversion of sample concentration and final comparative analysis, making the analysis difficult.
[0046] Example 2 like Fig. 2 As shown in this embodiment, an electrophoretic separation test method for detecting multiple solutes in a solution includes the following steps: Step 1: Fabrication of a microfluidic chip. The microfluidic chip, from top to bottom, comprises: a first insulating mounting frame 01, a first limiting plate 02, a set of barriers 03, a set of electrodes 04, a second limiting plate 05, and a second insulating mounting frame 06. The first insulating mounting frame 01 has a length of 50mm and a width of 50mm. The length and width of the second insulating mounting frame 06 are the same as those of the first insulating mounting frame 01. The electrodes 04 have a T-shaped cross-section and a length of 30mm, a width of 5mm, and a thickness of 3mm. The first limiting plate 02 has a length of 40mm, a width of 40mm, and a height of 3.5mm. The length, height, and width of the second limiting plate 05 are the same as those of the first limiting plate 02. The barriers 03 have a length of 30mm, a width of 5mm, and a height of 3mm. Step 2: Prepare terahertz metasurface sensor 08; wherein, the terahertz metasurface sensor 08 has a length of 30 mm, a width of 30 mm, and a thickness of 500 μm; Step 3: Prepare a porous hydrogel 09; the porous hydrogel 09 has a length of 30 mm, a width of 30 mm, and a thickness of 2.5 mm; a sample groove 10 for containing the target solution is formed on the porous hydrogel 09; the sample groove 10 has a length of 5 mm, a width of 5 mm, and a height of 1.5 mm; Step 4: First, place the second limiting plate 05 into the limiting boss 0707 on the upper surface of the second insulating mounting bracket 06; then, place a set of enclosures 03 and a set of electrodes 04 on the upper surface of the second limiting plate 05 to form a placement groove 11; next, place the terahertz metasurface sensor 08 into the placement groove 11, and then place the porous hydrogel 09 on the upper surface of the terahertz metasurface sensor 08. Requirements: the bottom surface of the porous hydrogel 09 must be completely in contact with the upper surface of the terahertz metasurface sensor 08, and both ends of the porous hydrogel 09 must be completely in contact with a set of electrodes 04; then, drop the mixed solution to be tested into the sample groove 10 of the porous hydrogel 09; next, place the first limiting plate 02 on the upper surface of the porous hydrogel 09; finally, place the first insulating mounting bracket 01 on the surface of the first limiting plate 02, and encapsulate and fix the first insulating mounting bracket 01 and the second insulating mounting bracket 06 with bolts.
[0047] S4. Apply a bias voltage to the electrode 04 assembly at both ends of the porous hydrogel 09 and continue electrophoresis for a first preset time, wherein the voltage difference between the two sides is set to 30V; the first preset time for electrophoresis is 8min. S5. Sensing and Detection: First, loosen the bolts between the first insulating mounting bracket 01 and the second insulating mounting bracket 06, then remove the first insulating mounting bracket 01; then place the remaining structural parts in a constant temperature drying oven and continue drying at a preset temperature for a second preset time until a suitable amount of various solutes 12 precipitate at the junction of the porous hydrogel 09 and the terahertz metasurface sensor 08; wherein, the drying temperature of the constant temperature drying oven is set to 30℃; and the second preset drying time is 8 minutes. S6. Position the terahertz metasurface sensor 08 according to the position of the central spot of the terahertz time-domain spectrometer, and perform sensing tests on the points where the precipitated solute 12 is deposited in sequence.
[0048] This embodiment presents a novel method for detecting multi-solute mixed solutions, overcoming the limitation of existing terahertz sensing methods that struggle with multi-solute solutions. It achieves rapid separation of multiple solutes through electrophoresis, and subsequent drying avoids direct detection of the solvent fraction. Furthermore, compared to traditional methods that require separation before detection, this method is faster and simplifies concentration testing. The microfluidic chip required for this method is also inexpensive and easy to fabricate.
[0049] Example 3 like Fig. 2 As shown in this embodiment, an electrophoretic separation test method for detecting multiple solutes in a solution includes the following steps: Step 1: A microfluidic chip is fabricated. The microfluidic chip, from top to bottom, comprises: a first insulating mounting frame 01, a first limiting plate 02, a set of barriers 03, a set of electrodes 04, a second limiting plate 05, and a second insulating mounting frame 06. The first insulating mounting frame 01 has a length of 70mm and a width of 70mm. The length and width of the second insulating mounting frame 06 are the same as those of the first insulating mounting frame 01. The electrodes 04 have a T-shaped cross-section and a length of 60mm, a width of 5mm, and a thickness of 3mm. The first limiting plate 02 has a length of 60mm, a width of 60mm, and a height of 3.5mm. The length, height, and width of the second limiting plate 05 are the same as those of the first limiting plate 02. The barriers 03 have a length of 60mm, a width of 5mm, and a height of 3mm. Step 2: Prepare terahertz metasurface sensor 08; wherein, the terahertz metasurface sensor 08 has a length of 60 mm, a width of 60 mm, and a thickness of 500 μm; Step 3: Prepare a porous hydrogel 09; the porous hydrogel 09 has a length of 60 mm, a width of 60 mm, and a thickness of 2.5 mm; a sample groove 10 for containing the target solution is formed on the porous hydrogel 09; the sample groove 10 has a length of 5 mm, a width of 5 mm, and a height of 1.5 mm; Step 4: First, place the second limiting plate 05 into the limiting boss 0707 on the upper surface of the second insulating mounting bracket 06; then, place a set of enclosures 03 and a set of electrodes 04 on the upper surface of the second limiting plate 05 to form a placement groove 11; next, place the terahertz metasurface sensor 08 into the placement groove 11, and then place the porous hydrogel 09 on the upper surface of the terahertz metasurface sensor 08. Requirements: the bottom surface of the porous hydrogel 09 must be completely in contact with the upper surface of the terahertz metasurface sensor 08, and both ends of the porous hydrogel 09 must be completely in contact with a set of electrodes 04; then, drop the mixed solution to be tested into the sample groove 10 of the porous hydrogel 09; next, place the first limiting plate 02 on the upper surface of the porous hydrogel 09; finally, place the first insulating mounting bracket 01 on the surface of the first limiting plate 02, and encapsulate and fix the first insulating mounting bracket 01 and the second insulating mounting bracket 06 with bolts.
[0050] S4. Apply a bias voltage to the electrode 04 assembly at both ends of the porous hydrogel 09 and continue electrophoresis for a first preset time, wherein the voltage difference between the two sides is set to 50V; the first preset time for electrophoresis is 12min. S5. Sensing and Detection: First, loosen the bolts between the first insulating mounting bracket 01 and the second insulating mounting bracket 06, and remove the first insulating mounting bracket 01; then place the remaining structural parts in a constant temperature drying oven and continue drying at a preset temperature for a second preset time until a suitable amount of various solutes 12 precipitate at the junction of the porous hydrogel 09 and the terahertz metasurface sensor 08; wherein, the drying temperature of the constant temperature drying oven is set to 50℃; and the second preset drying time is 12 minutes. S6. Position the terahertz metasurface sensor 08 according to the position of the central spot of the terahertz time-domain spectrometer, and perform sensing tests on the points where the precipitated solute 12 is deposited in sequence.
[0051] The microfluidic chips required for this solution do not have high precision requirements; they can be machined on millimeter-level lathes and rapidly formed using additive manufacturing methods such as 3D printing. The chip structures are reusable and have a long lifespan. It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.
[0052] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.
Claims
1. A method for detecting multiple solutes in a solution by electrophoretic separation, characterized in that: Includes the following steps S1. Fabrication of microfluidic chips: First, the microfluidic chip pattern is obtained using drawing software, and then the microfluidic chip is obtained using 3D printing technology for later use; S2. Fabrication of terahertz metasurface sensor: After forming the designed metasurface pattern on the substrate using photolithography, a terahertz metasurface sensor is obtained for later use; S3. Preparation of porous hydrogel: Pour the hydrogel into a mold to form a layered precursor, then freeze the layered precursor at low temperature to crystallize the water in the solution, and finally thaw at low temperature to obtain a porous hydrogel for later use. S4. Electrophoretic solute separation: Take the terahertz metasurface sensor from step S2 and the porous hydrogel from step S3 and place them in the microfluidic chip from step S1. Then, take the mixed solution to be detected and drop it into the groove of the porous hydrogel. After fixing the microfluidic chip, apply a bias voltage to the electrode components at both ends of the porous hydrogel and continue electrophoresis for a first preset time. S5. Sensing and Detection: The microfluidic chip with terahertz metasurface sensor and porous hydrogel is placed in a constant temperature drying oven and dried continuously at a preset temperature for a second preset time until a suitable amount of various solutes are precipitated at the junction of porous hydrogel and terahertz metasurface sensor; then, the precipitated solutes are sequentially sensed and tested using a terahertz time-domain spectrometer.
2. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 1, characterized in that, In step S5, the bias voltage is applied as follows: the voltage difference between the two sides is set to 30-50V; the first preset electrophoresis time is 8-12min.
3. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 1, characterized in that, In step S6, the drying temperature of the constant temperature drying oven is set to 30-50℃; the second preset drying time is 8-12 minutes.
4. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 1, characterized in that, Step S1, which involves fabricating a microfluidic chip, includes the following sub-steps: S11. Use SolidWorks or UG drawing software to obtain model drawings of the first insulating mounting frame, the second insulating mounting frame, the first limiting plate, the second limiting plate, a set of enclosures and a set of electrodes in sequence; S12. Convert the model diagrams in step S11 into STL or OBJ format diagrams in sequence; S13. Import the format diagram from step S12 into slicing software: Cura or Simplify3D, then adjust the position and set the size and fill parameters to generate G-code; S14. Transfer the G code from step S13 to the 3D printer via USB, SD card, or Wi-Fi; S15. On the control panel of the 3D printer, select the G-code file uploaded in step S14, click Start Printing, and you will get a structural product consisting of a first insulating mounting frame, a second insulating mounting frame, a first limiting plate, a second limiting plate, a set of enclosures, and a set of electrodes. S16. Place the second limiting plate on the second insulating mounting bracket, then place the enclosure and electrode on the upper surface of the second limiting plate. The enclosure and electrode form a groove for placing the terahertz metasurface sensor and the porous hydrogel. Next, place the first limiting plate on the upper surface of the enclosure and electrode. Finally, place the second insulating mounting bracket on the upper surface of the first limiting plate and fix the first and second insulating mounting brackets with bolts to obtain the microfluidic chip.
5. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 4, characterized in that, In step S15 above, the 3D printer uses TPX (4-methyl-1-pentene) as raw material when printing the first limiting plate and the second limiting plate.
6. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 4, characterized in that, In step S15 above, the 3D printer uses any one of the following raw materials when printing the first insulating fixing frame and the second insulating mounting frame: PLA (polylactic acid), ABS (acrylonitrile-butadiene-styrene copolymer), PETG (polyethylene terephthalate-1,4-cyclohexanediol ester), and PEI (polyetherimide).
7. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 4, characterized in that, In step S15 above, the 3D printer uses any one of the following raw materials when printing electrodes: pure copper, chromium zirconium copper alloy, GRCop alloy, and copper-nickel alloy.
8. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 1, characterized in that, Step S2, which involves preparing a terahertz metasurface sensor, includes the following sub-steps: S21. Design metasurface structure patterns using electromagnetic simulation software (CST); S22. After ultrasonically cleaning the substrate with acetone or isopropanol to remove impurities, dry it for later use. S23. Take the substrate from step 22 and coat the substrate surface with photoresist; then cover the transparent substrate with the metasurface structure pattern from step S21 onto the photoresist, and then form the photoresist pattern of the metasurface structure on the substrate through ultraviolet light exposure and development process. S24. A metal thin film is deposited on the substrate surface of the photoresist pattern formed in step S23 by electron beam evaporation. Then, an etching process is used to remove the metal parts that are not protected by the photoresist to form a metal metasurface structure. Finally, the photoresist is removed to obtain the terahertz metasurface sensor.
9. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 1, characterized in that, The substrate in step S22 is prepared from any one of the following materials: fused silica, borosilicate glass, or sapphire.
10. The electrophoretic separation test method for detecting multiple solutes in solution according to claim 1, characterized in that, The preparation of porous hydrogels by S3 includes the following sub-steps: S31: Select gelatin and / or polyvinyl alcohol, dissolve them in water, stir evenly to prepare a solution of a certain concentration, and set aside for later use; S32: The solution prepared in step S31 is used to prepare a mixed solution containing bubbles using the modified Tessari method, for later use; S33: Transfer the mixed solution containing air bubbles from step S32 into a mold to form a layered precursor. Then, place the layered precursor in a refrigerator and freeze it for a certain period of time to allow the solvent water to crystallize into ice crystals, forming a porous layered structure for later use. S34: Place the porous layered structure from step S33 into a freeze dryer for freeze drying, and then soak it in TBE buffer solution to obtain a porous hydrogel with a bubble structure.