Microfluidic chip based on electroosmotic effect and stress regulation method thereof

Abstract

The application belongs to the technical field of ultra-precision machining, and discloses a micro-fluidic chip based on electroosmotic effect and a stress regulation method thereof. The micro-fluidic chip is internally provided with a plurality of solution channels. The solution channels are of a serpentine reciprocating structure, one end of which is provided with a channel inlet, and the other end is provided with a channel outlet. The side of the solution channels facing the bottom of the micro-fluidic chip is provided with a plurality of inflection points which are arranged at intervals. The inflection points are close to the bottom of the micro-fluidic chip and are distributed on the micro-fluidic chip in the horizontal direction. Electrodes are further arranged on the solution channels. The application combines the electroosmotic effect with the micro-fluidic technology, and realizes high-precision dynamic stress regulation through gradient flow channel design, composite driving liquid formula and hysteresis compensation algorithm, thereby solving the problems of response hysteresis and insufficient precision of pressure control in traditional polishing technology, and providing a new technical approach for ultra-precision machining of large-aperture optical elements for inertial confinement nuclear fusion devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ultra-precision machining, in particular to a microfluidic chip based on electroosmotic effect and a stress regulation method thereof. BACKGROUND

[0002] Inertial confinement fusion (ICF) devices (such as the National Ignition Facility NIF in the United States) rely on high-power laser systems, and their performance directly depends on the surface accuracy of large-aperture optical elements. At present, in the manufacturing process of such optical elements (such as mirrors, lenses, etc.), the polishing link plays a decisive role in the final surface accuracy. However, the traditional polishing technology mainly relies on the mechanical properties of the polishing disc to regulate the pressure distribution, which has problems such as response lag and insufficient control accuracy, and it is difficult to meet the stringent requirements of high-power lasers on the full-band error of optical elements. Especially in the machining of large-aperture optical elements, the traditional method is easy to cause local stress unevenness, affecting the surface convergence efficiency. Therefore, it is urgent to develop a high-precision and real-time controllable polishing pressure regulation technology to improve the machining precision and efficiency of optical elements. SUMMARY

[0003] The present application aims to provide a microfluidic chip based on electroosmotic effect and a stress regulation method thereof to solve the problems raised in the background.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] A microfluidic chip based on electroosmotic effect, wherein a plurality of solution channels are arranged inside the microfluidic chip, the solution channels have a snake-shaped reciprocating structure, one end has a channel inlet, the other end has a channel outlet, the side of the solution channel facing the bottom of the microfluidic chip has a plurality of spaced-apart inflection points, the plurality of inflection points are close to the bottom of the microfluidic chip and are distributed in the horizontal direction of the microfluidic chip, and an electrode is arranged on the solution channel.

[0006] Further, the aperture of the solution channel gradually increases from the channel inlet to the channel outlet.

[0007] Further, a plurality of solution channels are uniformly arranged in the microfluidic chip, each solution channel is arranged along the radial direction of the microfluidic chip, one end of the solution channel close to the center of the microfluidic chip has a channel inlet, and one end of the solution channel close to the edge of the microfluidic chip has a channel outlet, and the channel inlets of all the solution channels are connected together.

[0008] The present application also provides a stress regulation method for a microfluidic chip based on electroosmotic effect as described above, comprising the following steps:

[0009] Step 1: design and prepare the microfluidic chip;

[0010] Step 2, preparation of electroosmotic driving liquid;

[0011] Step 3, filling the electroosmotic driving liquid to the microfluidic chip to obtain the electroosmotic driving microfluidic chip;

[0012] Step 4, building a test platform for stress regulation test;

[0013] Step 5, establishing a stress regulation strategy;

[0014] Step 6, hysteresis optimization for the hysteresis effect under the stress regulation strategy.

[0015] Further, the step 1 comprises:

[0016] Step 1.1, using a drawing software to design the internal solution flow channel structure of the microfluidic chip; installing electrodes on the solution channel;

[0017] Step 1.2, preparing a mold and completing the molding of the microfluidic chip;

[0018] Step 1.3, placing the glass top plate in a vacuum chamber, sputtering indium tin oxide to form a film, and then coating glue, and then performing ultraviolet exposure, development, etching, and cleaning to obtain the electrode;

[0019] Step 1.4, using plasma treatment to bond polydimethylsiloxane and the glass top plate to seal the microfluidic chip.

[0020] Further, the step 2 comprises:

[0021] Step 2.1, mixing 10%-15% hydrochloric acid, 25%-35% sodium hydroxide, and 50%-60% anhydrous ethanol according to the mass ratio to prepare a solution with pH=8-10, and adding sodium dodecyl sulfate as a surfactant to obtain a buffer solution;

[0022] Step 2.2, dissolving an appropriate amount of potassium chloride in water to prepare a 0.4-0.6 mol / L potassium chloride conductive solution;

[0023] Step 2.3, mixing the potassium chloride solution prepared in step 2.2 and the buffer solution prepared in step 1 according to the equal volume ratio, and adding 0.4%-0.6% suspension concentrate to prevent precipitation, and using a magnetic stirrer to mix thoroughly to obtain the electroosmotic driving liquid.

[0024] Further, the step 3 comprises:

[0025] Using a catheter to connect the microfluidic chip, the sample reservoir, and the pressure controller, the electroosmotic driving stress regulation chip is prepared.

[0026] Further, the step 4 comprises:

[0027] Step 4.1, build an experimental platform, including fused quartz optical elements to be processed, electroosmotic driving stress control chip, power control system, computer system, laser light source, high-speed camera system;

[0028] Step 4.2, using spectral processing means, separate the low, medium and high frequency surface error of the fused quartz optical element, and then further subdivide the medium frequency error into PSD1 and PSD2 two frequency ranges, calculate the pressure difference of the error in the stress control domain according to the Preston equation, and construct the ideal contact stress distribution characteristics respectively;

[0029] Step 4.3, complete the self-checking of the experimental platform system and connect the power supply with each indium tin oxide electrode to form a closed loop, then inject the electroosmotic driving liquid without bubbles; Three driving modes are set, including pure pressure driving, discrete voltage-pressure coupling driving and continuous voltage-pressure coupling driving, the response is monitored in real time through the stress sensor and the data is collected; Finally, through time domain analysis and error evaluation, the feasibility and control accuracy of the electroosmotic control method are verified, and the contact stress control is consistent with the ideal contact stress distribution.

[0030] Further, the step 5 comprises:

[0031] Step 5.1, through discrete voltage-pressure coupling driving, study the distribution characteristics of the reservoir stress of the electroosmotic driving microfluidic chip, and select a reasonable voltage range as the actual control voltage range;

[0032] Step 5.2, based on the influence law of discrete voltage on the stress of the solution channel, adopt continuous voltage-pressure coupling driving, use the waveform generator to switch different amplitude, frequency and waveform, and study the stress distribution of different flow channel walls.

[0033] Further, the step 6 comprises:

[0034] Step 6.1, the electroosmotic driving microfluidic chip composed of the microfluidic chip and the electroosmotic driving liquid is regarded as a resistance system, and the following physical conductance model of the electroosmotic driving microfluidic chip is established:

[0035]

[0036] Wherein, is the tunneling resistance, A is the cross-sectional area of the solution flowing through the solution channel, J is the tunneling current density, V is the potential difference, e is the elementary charge, m is the mass of a single electron, h is the Planck constant, exp is the natural exponential function, d is the distance between the agglomerated particles, λ is the energy barrier height polydimethylsiloxane, and S is the cross-sectional area of the tunneling region;

[0037] Step 6.2, establish the relative resistance change formula for theoretical prediction:

[0038]

[0039]

[0040] wherein, is the relative resistance, is the resistance change, is the resistance of the experimental platform control system in the original state, E is the electric field intensity, and are the strain and stress generated by the microfluidic chip respectively, is the Poisson ratio of the polydimethylsiloxane material, is the elastic modulus of the polydimethylsiloxane material;

[0041] The calculation formula of the relative conductivity is introduced:

[0042]

[0043] wherein, and respectively represent the conductivity of the electroosmotic driving liquid in the deformed state and the initial state of the solution channel, is the velocity vector;

[0044] The hysteresis degree is introduced:

[0045]

[0046] wherein DH is the hysteresis degree, AS and AR are the areas of the tensile curve and the release curve of the microfluidic chip material respectively;

[0047] Step 6.3, establish the transfer function model of the experimental platform control system, and accurately identify the hysteresis time constant; based on this hysteresis time constant, design a digital pre-compensator to correct the phase in advance before the output of the control signal; by adjusting the compensation parameters in real time, the accurate matching of the voltage waveform and the stress characteristics of the control system is realized;

[0048] According to the hysteresis optimization strategy, the electroosmotic driving liquid formula is optimized, the polydimethylsiloxane substrate particles are added to control the agglomerated particle distance below 140-160 nm, the potassium chloride concentration is controlled at 3%-4%, and the control voltage phase is advanced π / 16-π / 18.

[0049] Compared with the prior art, the beneficial effects of the present application are that the present application actively designs and prepares an electroosmotic driving microfluidic chip with ideal control effect. By studying the solution channel and interdigital electrode configuration and the component content of the electroosmotic driving liquid, a microfluidic chip with linear volt-ampere characteristics and an electroosmotic driving liquid with good electroosmotic driving performance are prepared. By establishing an electroosmotic driving mathematical model, the influence of voltage on solution flow rate, fluid pressure and reservoir stress is predicted, and the comparison of experimental results ensures that the prediction error is within 10%. Considering the response lag characteristics under the electroosmotic stress regulation strategy, an optimized control strategy is proposed, which provides a new method for the control of contact stress in the polishing process. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 It is a use state structure schematic diagram of a microfluidic chip based on electroosmotic effect of the present application.

[0051] Figure 2 It is a longitudinal partial cross-section structure schematic diagram of a microfluidic chip based on electroosmotic effect of the present application, and the electrode is not shown in the figure.

[0052] Figure 3 It is a longitudinal partial cross-section structure schematic diagram of a microfluidic chip based on electroosmotic effect of the present application, and the electrode is shown in the figure.

[0053] Figure 4 It is a stress regulation method flow chart of a microfluidic chip based on electroosmotic effect of the present application.

[0054] Figure 5 It is a curve graph of the influence of pH value on electroosmotic speed in the present application.

[0055] Figure 6 It is a solution channel wall stress distribution graph after continuous voltage phase preposition in the present application.

[0056] Figure 7 It is a physical conductance model graph of an electroosmotic driving microfluidic chip in the present application, and (a) is a physical conductance model schematic diagram, (b) is a tunneling resistance and different agglomerate particle spacing schematic diagram, (c) is a comparison graph of experimental and simulation curves of relative resistance change, and (d) is a graph of the number of particles with different contact characteristics under different strain rates.

[0057] Figure 8 It is a hysteresis distribution characteristic schematic diagram of a solution with different potassium chloride contents in the present application.

[0058] In the figure: rigid layer 1, microfluidic chip 2, solution channel 200, inflection point 2000, electrode 201, polishing pad 3. DETAILED DESCRIPTION

[0059] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0060] Please refer to Figures 1-3 A microfluidic chip based on electroosmotic effect, a plurality of solution channels 200 are arranged inside the microfluidic chip 2, the solution channels 200 are in a snake-shaped reciprocating structure, one end has a channel inlet, the other end has a channel outlet, the solution channels 200 have a plurality of spaced-apart inflection points 2000 towards one side of the bottom of the microfluidic chip 2, all the inflection points 2000 are close to the bottom of the microfluidic chip 2 and are distributed in the horizontal direction of the microfluidic chip, and electrodes 201 are further arranged on the solution channels 200, the electrodes 201 are preferably interdigital electrodes.

[0061] The microfluidic chip 2 is in a wafer-shaped structure, a plurality of solution channels 200 are uniformly arranged around the center of the microfluidic chip 2, each solution channel 200 is arranged along the radial direction of the microfluidic chip 2, so that the bottom of the microfluidic chip 2 is arrayed with inflection points 2000 (the inflection points 2000 are not exposed to the bottom of the microfluidic chip 2, but are as close to the bottom of the microfluidic chip 2 as possible). The solution channel 200 has a channel inlet at one end close to the center of the microfluidic chip 2 and a channel outlet at one end close to the edge of the microfluidic chip 2, and the channel inlets of all the solution channels 200 are connected together.

[0062] The cross section of the solution channel 200 is circular, and the aperture of the solution channel 200 gradually increases from the channel inlet to the channel outlet, so that the solution backflow can be reduced. Specifically, as shown in Figure 2 Each solution channel 200 is divided into five channel units, adjacent channel units are connected through V-shaped channels, and the widths of the five channel units from the channel inlet to the channel outlet are 0.1mm, 0.2mm, 0.3mm, 0.4mm and 0.5mm, respectively. The angle of the V-shaped channel is 100°-140°, preferably 120°, and the inflection point 2000 is the turning point of the V-shaped channel.

[0063] As shown in Figure 1 When the microfluidic chip 2 of the present application is used, it is connected together with the rigid layer 1 and the polishing pad 3, specifically, the microfluidic chip 2 is fixedly attached to the bottom of the rigid layer 1, the polishing pad 3 is fixedly attached to the bottom of the microfluidic chip 2, and the polishing pad 3 corresponds to the inflection points 2000 on the microfluidic chip 2.

[0064] The full-surface full-band error of the workpiece is extracted before polishing processing, the ideal contact stress distribution removing full-band error is obtained, the solution is introduced during polishing and the voltage value corresponding to the ideal contact stress is introduced, so that the solution in the channel realizes directional movement at a certain speed under the action of electroosmosis, collides with the solution channel wall at the corner to obtain reservoir stress, the stress makes the chip material produce deformation, which is transmitted to the polishing pad through physical contact, so that the polishing pad can accurately remove the material. The size of the solution channel stress is related to the movement speed of the solution. By studying the different component ratios of the solution, the electroosmotic driving liquid with the best driving effect is obtained. By changing the voltage value, the movement speed of the solution can be accurately controlled to control the size of the reservoir stress obtained.

[0065] Referring to Figures 1-8 A stress regulation method of a microfluidic chip based on electroosmotic effect, comprising the following steps:

[0066] Step 1, design and preparation of microfluidic chip, comprising:

[0067] Step 1.1, using AutoCAD to design the internal solution flow channel structure of the microfluidic chip, the designed solution channel has a gradient size of 0.5mm-0.4mm-0.3mm-0.2mm-0.1mm, and a 120° V-shaped channel is arranged at each contraction position to reduce the turbulent effect of the solution when the cross-sectional area changes, so as to ensure that the fluid pressure remains highly stable during channel transmission, as shown in Figure 2 .

[0068] Step 1.2, selecting interdigital electrodes as the excitation power structure, the material is selected as indium tin oxide electrodes, the electrode depth is 5mm, the interdigital electrode spacing is 10mm, and the electrode depth is 5mm, which is arranged on both sides of the solution channel with each size width, as shown in Figure 3 .

[0069] Step 1.3, mold preparation. The designed solution channel structure is etched on the chromium-plated glass photomask. A 0.3mm thick resin is coated on the surface of the silicon wafer, and after covering the photomask, ultraviolet exposure is performed, and only the channel area is solidified. After development, the unexposed resin is dissolved to form a relief microfluidic mold. The channel height is determined by the thickness of the resin. Finally, the mold is treated with silane to facilitate subsequent demolding.

[0070] Step 1.4, microfluidic chip forming. After mixing polydimethylsiloxane and crosslinking agent, it is injected into the mold and cured at high temperature. After demolding, the fluid channel inlet and outlet matched with the catheter are processed by polydimethylsiloxane puncher.

[0071] Step 1.5, place the glass top plate on the vacuum chamber rotary table, and load the indium tin oxide target material into the ion beam sputtering target gun. The vacuum chamber is evacuated to 10 -4After the pressure is reduced to 10-6Pa, the indium tin oxide target is bombarded by ion beam to deposit indium tin oxide film on the glass. After reaching the desired thickness, the glass is removed and coated with photoresist, exposed to ultraviolet light, developed, etched to remove unprotected indium tin oxide, and finally cleaned to obtain patterned indium tin oxide electrode

[0072] Step 1.6, polydimethylsiloxane and glass top plate are bonded by plasma treatment to seal the microfluidic chip.

[0073] Step 2, prepare the electroosmotic driving liquid, including:

[0074] Step 2.1, mix 15% hydrochloric acid, 30% sodium hydroxide and 55% anhydrous ethanol according to the mass ratio to prepare a solution with pH=9, and add an appropriate amount of sodium dodecyl sulfate (SDS) as a surfactant to obtain a buffer solution;

[0075] Step 2.2, dissolve 63.3g of potassium chloride in 1700mL of water to prepare a 0.5mol / L potassium chloride conductive solution;

[0076] Step 2.3, mix the potassium chloride solution with the pH=9 buffer solution in a volume ratio of 1:1, and add 0.5% suspension concentrate to prevent precipitation, mix thoroughly with a magnetic stirrer to obtain the electroosmotic driving liquid, Figure 5 a curve showing the influence of different Ph values on the electroosmotic speed.

[0077] Step 3, fill the electroosmotic driving liquid into the microfluidic chip to obtain the electroosmotic driving microfluidic chip, including:

[0078] Connect the microfluidic chip, sample reservoir and pressure controller with a catheter, connect the inlet of the electroosmotic driving liquid to the channel with a width of 0.1mm, and the outlet to the channel with a width of 0.5mm, and the electroosmotic driving stress control chip is prepared.

[0079] Step 4, build a test platform for stress control test, including:

[0080] Step 4.1, build the experimental platform, which contains six core modules: 200mm fused quartz optical element to be processed (processing object), electroosmotic driving stress control chip (experimental carrier), power control system (electric field excitation), computer system (parameter control and data acquisition), laser light source (flow field illumination), high-speed camera system (dynamic response recording).

[0081] Step 4.2, use spectral processing method to separate low, medium and high frequency surface errors of the fused quartz optical element. Then further subdivide the medium frequency error into two frequency ranges of PSD1 and PSD2, calculate the pressure difference of the errors in the stress control domain according to the Preston equation, and construct the ideal contact stress distribution characteristics respectively.

[0082] Step 4.3, complete the experimental platform system self-checking and connect the power supply to each indium tin oxide electrode to form a closed loop, then bubble-free injection of electroosmotic driving liquid; three driving modes (pure pressure driving, discrete voltage-pressure coupling driving, continuous voltage-pressure coupling driving) are set up, the response is monitored in real time through the stress sensor and the data is collected; finally, the feasibility and control accuracy of the electroosmotic regulation method are verified through time domain analysis and error evaluation, and the contact stress regulation is consistent with the ideal contact stress distribution.

[0083] Step 5, establish a stress regulation strategy, including:

[0084] Step 5.1, through discrete voltage-pressure coupling driving, study the distribution characteristics of the reservoir stress of the electroosmotic driving microfluidic chip, and select a reasonable voltage range as the actual control voltage range;

[0085] Step 5.2, based on the influence law of discrete voltage on solution channel stress, adopt continuous voltage-pressure coupling driving, use the waveform generator to switch different amplitude, frequency and waveform, and study the stress distribution of different flow channel walls, as shown in Figure 6 .

[0086] Step 6, for the hysteresis effect under the stress regulation strategy, including:

[0087] Step 6.1, for the electrical response hysteresis caused by the agglomerated particles in the electroosmotic driving liquid, first, the electroosmotic driving microfluidic chip composed of the microfluidic chip and the electroosmotic driving liquid is regarded as a resistance system, and then the physical conductance model of the electroosmotic driving microfluidic chip is established as follows:

[0088]

[0089] wherein, is the tunneling resistance, A is the cross-sectional area of the solution flowing through the solution channel, J is the tunneling current density, V is the potential difference, e is the elementary charge, m is the mass of a single electron, h is the Planck constant, exp is the natural exponential function, d is the distance between the agglomerated particles, λ is the energy barrier height (1eV for polydimethylsiloxane), and S is the cross-sectional area of the tunneling region, which is assumed to be the same as the cross-sectional area of a single agglomerated particle. The relevant physical conductance model is shown in Figure 7 .

[0090] Step 6.2, for the influence of potassium chloride content in the electroosmotic driving liquid on the response hysteresis, in order to analyze the influence of potassium chloride content on the response hysteresis, first, the relative resistance change formula is established for theoretical prediction:

[0091]

[0092]

[0093] wherein, is the relative resistance, is the resistance change, is the resistance of the experimental platform control system in the original state, E is the electric field intensity, and are the strain and stress generated by the microfluidic chip, respectively, is the Poisson's ratio of the polydimethylsiloxane material, usually taken as 0.5, is the elastic modulus of the polydimethylsiloxane material.

[0094] The resistance-strain relationship of the potassium chloride solution was accurately characterized, and a calculation formula of relative conductivity was introduced:

[0095]

[0096] wherein, and represent the conductivities of the electroosmotic driving liquid in the deformed state and the initial state of the solution channel, respectively, is the velocity vector, and the hysteresis distribution characteristics of different potassium chloride content solutions are shown in Figure 8 .

[0097] In order to quantify the hysteresis, the hysteresis degree is introduced:

[0098]

[0099] wherein DH is the hysteresis degree, and AS and AR are the areas of the tensile curve and the release curve of the microfluidic chip material, respectively.

[0100] Step 6.3, in order to solve the time lag problem of signal transmission and processing of the control system, an active control strategy based on voltage waveform pre-compensation is proposed. First, the transfer function model of the control system is established, and the time constant of the hysteresis is accurately identified; then based on this time constant of the hysteresis, a digital pre-compensator is designed to correct the phase in advance before the control signal is output; finally, through real-time adjustment of the compensation parameters, the voltage waveform and the stress characteristics of the control system are accurately matched.

[0101] According to the hysteresis optimization strategy, the electroosmotic driving liquid formula is optimized, the polydimethylsiloxane substrate particles are added to control the agglomerated particle distance to be below 150.58 nm, the potassium chloride concentration is controlled at 3.69%, and the control voltage phase is advanced by π / 12 (corresponding to 0.5s in time domain).

[0102] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A microfluidic chip based on electroosmotic effect, characterized in that, The microfluidic chip is internally uniformly ringed with a plurality of solution channels, each solution channel is arranged along the radial direction of the microfluidic chip, the solution channel has a channel inlet near one end of the center of the microfluidic chip and a channel outlet near one end of the edge of the microfluidic chip, the channel inlets of all solution channels are communicated together, the solution channel is a snake-shaped reciprocating structure, the solution channel has a plurality of spaced-apart inflection points on the side facing the bottom of the microfluidic chip, a plurality of the inflection points are near the bottom of the microfluidic chip and are distributed in the horizontal direction of the microfluidic chip, and an electrode is further arranged on the solution channel. Each solution channel is divided into a plurality of channel units, adjacent channel units are connected through V-shaped channels, and the turning points of the V-shaped channels are the inflection points.

2. The microfluidic chip based on electroosmotic effect according to claim 1, wherein, The pore size of the solution channel gradually increases from the channel inlet to the side of the channel outlet.

3. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 1 or 2, characterized in that, The method comprises the following steps: Step 1, designing and preparing a microfluidic chip; Step 2, preparing an electroosmotic driving liquid; Step 3, filling the electroosmotic driving liquid into the microfluidic chip to obtain an electroosmotic driving type microfluidic chip; Step 4, building a test platform for stress regulation test; Step 5, establishing a stress regulation strategy; Step 6, optimizing the hysteresis effect under the stress regulation strategy.

4. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 3, characterized in that, The step 1 comprises: Step 1.1, using a drawing software to design the internal solution flow channel structure of the microfluidic chip; and installing an electrode on the solution channel; Step 1.2, preparing a mold and completing the molding of the microfluidic chip; Step 1.3, placing a glass top plate in a vacuum cavity, sputtering indium tin oxide to form a film by an ion beam, and then coating glue, and then performing ultraviolet exposure, development, etching and cleaning to obtain the electrode; Step 1.4, bonding polydimethylsiloxane and the glass top plate by a plasma treatment method to seal the microfluidic chip.

5. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 3, characterized in that, The step 2 comprises: Step 2.1, mixing 10%-15% hydrochloric acid, 25%-35% sodium hydroxide and 50%-60% anhydrous ethanol according to the mass ratio to prepare a solution with pH=8-10, and adding sodium dodecyl sulfate as a surfactant to obtain a buffer solution; Step 2.2, dissolving a proper amount of potassium chloride in water to prepare a 0.4-0.6 mol / L potassium chloride conductive solution; Step 2.3, mixing the potassium chloride solution prepared in step 2.2 and the buffer solution prepared in step 1 according to an equal volume ratio, and adding 0.4%-0.6% suspension concentrate to prevent precipitation, and fully mixing them by using a magnetic stirrer to obtain the electroosmotic driving liquid.

6. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 3, characterized in that, The step 3 comprises: The electroosmotic driving type stress regulation chip is prepared by connecting the microfluidic chip, the sample storage pool and the pressure controller by using a conduit.

7. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 3, characterized in that, The step 4 comprises: Step 4.1, building an experimental platform, including a fused quartz optical element to be processed, an electroosmotic driving type stress regulation chip, a power supply control system, a computer system, a laser light source and a high-speed camera system; Step 4.2, using a spectrum processing method to separate the low, medium and high frequency surface error of the fused quartz optical element, and then further subdividing the medium frequency error into two frequency ranges of PSD1 and PSD2, calculating the pressure difference of the errors in the two frequency ranges on the stress control domain according to the Preston equation, and respectively constructing ideal contact stress distribution characteristics; Step 4.3, complete the experimental platform system self-test and connect the power supply with each indium tin oxide electrode to form a closed loop, then bubble-free injection of electroosmotic driving liquid; three driving modes are set, including pure pressure driving, discrete voltage-pressure coupling driving, continuous voltage-pressure coupling driving, real-time response monitoring and data collection are realized through stress sensor; finally, the feasibility and control accuracy of electroosmotic regulation method are verified through time domain analysis and error evaluation, and the contact stress regulation is consistent with the ideal contact stress distribution.

8. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 3, characterized in that, The step 5 comprises: Step 5.1, through discrete voltage-pressure coupling driving, the distribution characteristics of reservoir stress of electroosmotic driving microfluidic chip are studied, and a reasonable voltage range is selected as the actual control voltage range; Step 5.2, based on the influence law of discrete voltage on solution channel stress, continuous voltage-pressure coupling driving is adopted, different amplitude, frequency and waveform are switched by waveform generator, and the stress distribution of different flow channel wall is studied.

9. The stress regulation method of the microfluidic chip based on the electroosmotic effect according to claim 3, characterized in that, The step 6 comprises: Step 6.1, the electroosmotic driving microfluidic chip composed of microfluidic chip and electroosmotic driving liquid is regarded as a resistance system, and the following physical conductance model of electroosmotic driving microfluidic chip is established: wherein, is the tunneling resistance, A is the cross-sectional area of the solution flow through the solution channel, J is the tunneling current density, V is the potential difference, e is the elementary charge, m is the mass of a single electron, h is the Planck constant, exp is the natural exponential function, d is the distance between the agglomerated particles, l is the energy barrier height polydimethylsiloxane, S is the cross-sectional area of the tunneling region; Step 6.2, the relative resistance change formula is established for theoretical prediction: wherein, is the relative resistance, is the resistance change, is the resistance of the experimental platform control system in the original state, E is the electric field intensity, and are the strain and stress generated by the microfluidic chip, respectively, is the Poisson's ratio of the polydimethylsiloxane material, is the elastic modulus of the polydimethylsiloxane material; The calculation formula of relative conductivity is introduced: wherein and respectively represent the electrical conductivity of the electroosmotic driving liquid in the deformed state and in the initial state of the solution channel, is the velocity vector; The hysteresis degree is introduced: Wherein DH is the hysteresis degree, AS and AR are the areas of the tensile curve and the release curve of the microfluidic chip material respectively; Step 6.3, the transfer function model of the control system of the experimental platform is established, and the time constant of the hysteresis is accurately identified; based on the hysteresis time constant, a digital pre-compensator is designed to correct the phase in advance before the output of the control signal; through real-time adjustment of compensation parameters, the accurate matching of voltage waveform and stress characteristics of control system is realized; According to the hysteresis optimization strategy, the electroosmotic driving liquid formula is optimized, the polydimethylsiloxane matrix particles are added to control the agglomerated particle distance below 140-160 nm, the potassium chloride concentration is controlled at 3%-4%, and the control voltage phase is advanced π / 16-π / 18.

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