Flexible micro-flow pipeline preparation method and preparation device based on in-situ electric heating

Abstract

The invention relates to a preparation method and a preparation device of a flexible micro-flow pipeline based on in-situ electric heating. The method comprises the following steps: S1, preparing a polymer precursor solution; s2, placing an electric heating wire into the polymer precursor solution for first in-situ electric heating, and centrifugally rotating the electric heating wire after heating; s3, the electric heating wire with the polymer film formed on the surface is electrified and heated for the second time; s4, immersing the electric heating wire with the micro-flow pipeline attached to the surface into a swelling solution to be swelled and separated from the electric heating wire, so as to obtain a swelled micro-flow pipeline; s5, after the swelling solution in the swelling micro-flow pipeline is volatilized, the micro-flow pipeline is recovered to the non-swelling state, and the flexible micro-flow channel facing the flow sensor is obtained. The device comprises a first solution tank, a second solution tank, a power supply module, a control module and an electric heating wire. The preparation method of the flexible micro-flow pipeline has the characteristics of convenience, rapidness, low energy consumption, high preparation efficiency and the like, and the prepared flexible micro-flow pipeline is good in surface morphology and uniform in wall thickness.

Description

Technical Field

[0001] The invention relates to the field of flexible microfluidic pipeline preparation, and in particular to a flexible microfluidic pipeline preparation method and a preparation device based on in-situ electric heating. Background Art

[0002] Polymer flexible microfluidic pipes play a vital role in the fields of biotechnology, chemical engineering and medical diagnosis. Traditional methods for preparing polymer pipes include extrusion molding, injection molding, blow molding, hot pressing, 3D printing, etc.

[0003] Extrusion molding is to heat the polymer material to a molten state and then extrude it through a mold to form a pipe. However, this method is only applicable to the production of pipes with larger diameters and wall thicknesses, and is not applicable to the manufacture of micron-sized hollow pipes. Injection molding is a method in which molten polymer material is injected into a closed mold, and the product is demolded after cooling and solidification. Injection molding can produce tiny polymer pipes with complex shapes, but when the wall of the micro-pipe is thin and only micron-sized, the mold is difficult to detach and the pipe wall is easily damaged. Blow molding is to place the molten polymer material in a mold, and then expand it and adhere to the inner wall of the mold by blowing air to form a hollow pipe. The hot press molding method is to place the polymer material in a heated mold and apply pressure to shape it. This method is suitable for the production of tiny polymer pipes with thin walls and high dimensional accuracy requirements. These methods require the use of molds and complex hollow pipe extrusion devices. The polymer material needs to be heated and melted in advance and maintained at a certain temperature during the production process. After the production is completed, a demolding process is required. The overall energy consumption of the process is large, and the high temperature environment has high requirements for site and equipment. In the 3D printing method, the original mold cannot be removed quickly and efficiently after 3D printing. These methods cannot prepare low modulus and ultra-thin wall microchannels, and cannot be applied to the preparation of pipes in flow sensors.

[0004] Patent CN109071942B discloses a technical solution of immersing a metal wire in a pool of heat-curable polymer, heating the metal wire for a period of time and then pulling it out for secondary heating, immersing the polymer-coated wire in a liquid bath for ultrasonic treatment after secondary heating, thereby loosening the contact between the polymer and the wire, and removing the metal wire from the polymer-coated wire, thereby producing a polymer microtube. This technical solution was found in actual application: when preparing microfluidic pipes, there are problems of rough outer surface and uneven wall thickness. The uneven wall thickness is not only reflected in the uneven wall thickness at the same cross section, but also in the uneven wall thickness in the middle area and end area of ​​the pipe. The thinner the pipe wall thickness, the more serious the phenomenon of rough outer surface and uneven thickness.

[0005] Therefore, designing a convenient, fast, low-energy, ultra-thin and uniform-walled flexible microfluidic pipeline preparation method is an urgent problem to be solved. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that low modulus and ultra-thin wall thickness microchannels for flow sensing cannot be realized in the existing microchannel preparation technology.

[0007] In a first aspect, the present application provides a method for preparing a flexible microfluidic conduit based on in-situ electrical heating, which can be used in a micro-sized biosensor, and specifically can be used for sensing and long-term monitoring of microfluid flow rate. The preparation method specifically comprises the following steps:

[0008] S1, preparing a polymer precursor solution, wherein the polymer precursor solution is thermally cured to form a flexible microfluidic channel, and the thermal curing temperature is 60-150° C.;

[0009] S2, placing the heating wire part into the polymer precursor solution, heating the heating wire for the first time by energizing, and after heating, moving the heating wire away from the polymer precursor solution, centrifugally rotating the heating wire, and obtaining the heating wire with a polymer film formed on the surface;

[0010] The centrifugal rotation axis of the heating wire is an axis in the vertical direction of the circular cross section or an axis in the extending direction of the circular cross section;

[0011] S3, heating the heating wire with the polymer film formed on the surface for a second time to obtain the heating wire with the microfluidic channel attached to the surface;

[0012] S4, immersing the heating wire with the microfluidic pipeline attached to the surface into a swelling solution, the microfluidic pipeline swells and separates from the heating wire, and a swollen microfluidic pipeline is obtained, and the swelling solution has a swelling effect on the microfluidic pipeline;

[0013] S5. After the swelling solution in the swollen microfluidic channel is volatilized, a flexible microfluidic channel is obtained.

[0014] In the traditional method of preparing microfluidic channels, after the heating wire is immersed in the precursor solution and heated for the first time and pulled out, part of the precursor solution will remain and hang on the surface of the heating wire attached with the preliminary cured polymer film. Due to the liquid properties of the precursor solution (such as high viscosity), it will cause uneven distribution on the surface. These residual precursor solutions unevenly distributed on the surface will further cause uneven wall thickness of the microfluidic channel when heated for the second time, and the channel wall surface is rough. The outer surface of the microfluidic channel prepared by the traditional method is rough and the wall thickness is uneven. When applied to biosensors such as flow sensors, the rough outer surface needs to undergo additional processing steps, and the uneven wall thickness makes it difficult to exert its stable sensing performance.

[0015] More specifically, the heating wire is an alloy wire, and the resistance of the alloy wire is 1 to 10Ω / cm; in step S2, during the first power-on heating process, the power-on voltage is 0.1 to 0.3V / cm, and the power-on time is 30 to 60s. The present application controls the temperature of the alloy wire when it is heated by setting the alloy wire resistance and the power-on voltage, and the heating temperature of the alloy wire adapts to the solidification temperature of the polymer precursor solution. In step S2, after the alloy wire is heated, the polymer precursor is uniformly solidified on the surface of the alloy wire to form a polymer film. The longer the power-on heating time, the thicker the film.

[0016] More specifically, in step S2, when the electric heating wire is centrifugally rotated, the rotation speed is 500-1500 rpm, and the rotation time is 3-10 seconds. During the centrifugation process, the residual and suspended precursor solution on the surface of the electric heating wire can be effectively removed, and secondary heating is performed after centrifugation, so that the wall thickness of the prepared microfluidic channel is uniform and the outer surface of the channel is smooth and not rough.

[0017] Further specifically, in step S3, during the second power-on heating process, the power-on voltage is 0.1-0.3 V / cm, and the power-on time is 10-45 s. The power-on parameters of the heating process in step S2 and the power-on parameters of the second power-on heating process in step S3 may be different or the same, and the power-on parameters include the power-on voltage and the power-on time.

[0018] More specifically, the polymer precursor solution is selected from any one of a PDMS precursor solution, a PBAT precursor solution, a polyimide precursor solution, a thermoplastic elastomer, and a PVA precursor solution.

[0019] More specifically, the swelling solution is selected from any one of dichloromethane, chloroform, DMF, toluene, isopropanol, and n-hexane.

[0020] More specifically, in step S4, the heating wire with the microfluidic conduits uniformly attached to its surface is immersed in the swelling solution for 1 to 10 minutes.

[0021] More specifically, step S4 is as follows: immersing the alloy wire with the microfluidic pipe evenly attached to the surface into a swelling solution, controlling the alloy wire to shake, and causing the microfluidic pipe to swell and separate from the heating wire, thereby obtaining a swollen microfluidic pipe. The microfluidic pipe can be controlled to fall into the swelling solution after swelling and separating from the heating wire, or it can be controlled to fall outside the swelling solution.

[0022] In a second aspect, the present application provides a flexible microfluidic channel.

[0023] More specifically, the wall thickness of the flexible microfluidic conduit is no more than 300 μm.

[0024] In a third aspect, the present application provides a flexible microfluidic pipeline preparation device, including a first solution tank, a second solution tank, a power module, a control module and a heating wire;

[0025] The first solution pool contains a polymer precursor solution, and the second solution pool contains a swelling solution; the power module is connected to a control module, and the control module is used to heat at least one of the heating wires and clamp at least one of the heating wires to operate in the first solution pool, in the second solution pool, or in an area outside the first solution pool and the second solution pool;

[0026] The actions at least include: moving and rotating around the central axis in the vertical direction of the circular cross section of the heating wire.

[0027] To be more specific, a stirring device is provided in the first solution pool, and the stirring device is used to configure the polymer precursor solution. The stirring device can be set as a movable and detachable structure. At the same time, the first solution pool can also be provided with an interface corresponding to the exhaust device. After the precursor solution is stirred and configured, it can be directly connected to the exhaust device to quickly remove bubbles in the solution.

[0028] More specifically, a screen is provided in the second solution pool, and the screen is used to accommodate the microfluidic pipe detached from the second solution pool. The screen can be provided as a movable and detachable structure.

[0029] More specifically, the method further includes at least one of the following devices: a temperature sensor, a timer, a buzzer, a liquid level meter disposed in the first solution pool, and a liquid level meter disposed in the second solution pool.

[0030] The beneficial effects of this application are:

[0031] 1. This application designs a method for preparing a flexible microfluidic pipeline based on in-situ electric heating, which innovatively uses an electric heating wire to heat and solidify the polymer precursor solution twice, and the curing energy utilization rate is high during heating. With the optimization design of heating voltage, heating time, centrifugal rotation speed, and rotation time, an ultra-thin flexible microfluidic pipeline with a wall thickness of no more than 300μm and a Young's modulus of 0.1 to 0.5MPa can be prepared. The preparation method is convenient and fast, with low energy consumption, small site requirements, and high preparation efficiency.

[0032] 2. The flexible microfluidic pipeline preparation device designed in this application has the characteristics of small equipment size, strong adaptability to production sites, low equipment energy consumption, and high production efficiency. It can be used for the preparation of low-modulus and ultra-thin-wall microfluidic channels for flow sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic flow chart of the microfluidic pipeline preparation method in the present application;

[0034] Figure 2It is a schematic diagram of the rotation method during the centrifugation process in this application;

[0035] Figure 3 Schematic diagram of the appearance of the microfluidic pipeline of the embodiment and the comparative example of the present application;

[0036] Figure 4 is a schematic cross-sectional view of a microfluidic pipeline in Example 1 of the present application;

[0037] Figure 5 is a schematic cross-sectional view of a microfluidic pipeline in Comparative Example 3 of the present application;

[0038] Figure 6 It is a schematic diagram of the appearance of the microfluidic pipeline of comparative example 5 of the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the specific implementation methods of the present invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The flexible microfluidic pipeline preparation method based on in-situ electric heating designed in this application is suitable for polymer microfluidic pipelines with precursor solutions and polymers with a curing temperature between 60 and 150° C. The preparation method designed in this application can prepare flexible microfluidic pipelines with ultra-thin walls (no more than 300 μm).

[0041] Preparation method flow chart Figure 1 As shown, the specific steps include:

[0042] S1. Prepare a polymer precursor solution, which is determined by the type of microfluidic pipeline required. Stir the polymer main resin and the cross-linking agent in a specific ratio to mix them evenly and fully, and use a vacuum pump to remove bubbles in the solution after mixing. The vacuum pump pressure can be adjusted according to the actual bubble removal effect, and is preferably set between -0.08Mpa and -0.1Mpa.

[0043] In some specific embodiments, the polymer precursor solution can be selected from any one of PDMS precursor solution, PBAT precursor solution, polyimide precursor solution, thermoplastic elastomer, and PVA precursor solution. Taking PDMS precursor solution as an example, when configuring the PDMS precursor solution, the ratio of the polymer main resin to the cross-linking agent is 10:1. For other precursor solutions, suitable configuration methods and reagent configuration ratios can be selected according to actual needs.

[0044] S2. Place a certain length of the heating wire part into the polymer precursor solution. The length of the heating wire needs to be greater than the required length of the microfluidic pipeline. The length of the heating wire placed in the polymer precursor solution is the length of the microfluidic pipeline. The heating wire is heated for the first time. During the first heating, the polymer precursor is initially solidified on the surface of the heating wire. After heating for a period of time, the heating wire is removed from the polymer precursor solution and the removed heating wire is centrifugally rotated. During the rotation, the centrifugal force throws off the uncured polymer precursor solution hanging on the surface, and makes the thickness of the initially cured polymer attached to the surface more uniform, so as to obtain a heating wire with a polymer film uniformly attached to the surface.

[0045] In step S2, the heating wire can be selected from a heating rod made of copper wire, alloy wire or other materials. The heating wire can be a straight metal rod, or it can be an irregular metal rod with a certain shape that is not straight, for example, it can be a metal rod with a local curvature, and the curvature can be between 0.06 and 0.33. The diameter of the heating wire is the hollow inner diameter of the microfluidic channel, and the depth of the heating wire extending into the polymer precursor solution is the length of the microfluidic channel. The temperature of the heating wire during heating is controlled by controlling the power-on heating voltage, and the wall thickness of the microfluidic channel is regulated by the power-on heating time, the rotation speed during centrifugal rotation, and the rotation time. The selection of the heating wire is adjusted according to the size and shape of the microfluidic channel to be prepared.

[0046] In some specific embodiments, the electric heating wire is an alloy wire with a resistance of 1 to 10 Ω / cm. The voltage of the first heating is 0.1 to 0.3 V / cm, and the power-on time is 30 to 60 seconds.

[0047] In some specific embodiments, the centrifugal rotation axis of the heating wire is an axis in the vertical direction of the circular cross section or an axis in the extending direction of the circular cross section. Figure 2 As shown, there are three ways of the electric heating wire centrifugal process, among which method a is that the electric heating wire is vertically downward, and the electric heating wire rotates centrifugally around the axis in the vertical direction of the circular cross section, and the precursor solution suspended on the surface is thrown away to the annular area surrounded by the front, back, left and right; method b is that the electric heating wire is placed horizontally, and the electric heating wire rotates centrifugally around the axis in the vertical direction of the circular cross section, and the precursor solution suspended on the surface is thrown away to the annular area surrounded by the front, back, top and bottom; method c is that the electric heating wire is placed horizontally, one end of the electric heating wire is fixed vertically to the rotating axis, and the electric heating wire rotates centrifugally around the axis in the extension direction of the circular cross section, and the precursor solution suspended on the surface is thrown away to the annular area surrounded by the front, back, left and right. In method c, the coverage area of ​​the precursor solution thrown away is relatively small. In practical applications, the appropriate centrifugal method can be selected according to the space conditions of the operating environment. The rotation speed during the centrifugation process is preferably 500-1500rpm, and the rotation time is preferably 3-10s.

[0048] S3, heating the heating wire with the polymer film formed on the surface for the second time, the heating wire is still outside the polymer precursor solution during the second heating, the second heating process can further cure the polymer completely, and the heating wire with the microfluidic pipeline attached to the surface is obtained after the second heating. During the second heating process, the voltage and time of the heating can be the same as the heating control in step S2, and the voltage and time of the heating can also be adjusted according to the curing condition of the polymer microfluidic pipeline.

[0049] In some specific embodiments, the main purpose of the secondary heating is to completely cure the attached polymer. The secondary heating usually takes a shorter time than the first heating. The secondary voltage is 0.1-0.3 V / cm and the power-on time is 10-45 s.

[0050] S4, immersing the heating wire with the microfluidic pipeline attached to the surface into the swelling solution, and the immersion depth is preferably controlled to at least completely immerse the attached microfluidic pipeline. The microfluidic pipeline absorbs the swelling solution and swells. After swelling, the microfluidic pipeline is separated from the heating wire to obtain a swollen microfluidic pipeline. The swelling solution is an organic solvent that has a swelling effect on the polymer microfluidic pipeline, and the solvent type can be adjusted according to the type of polymer.

[0051] In some specific embodiments, the time for the electric heating wire to be immersed in the swelling solution is 1 to 10 minutes. If the immersion time is too short, the microfluidic pipeline will not swell sufficiently and will be difficult to fall off from the electric heating wire. If the immersion time is too long, the microfluidic pipeline may be damaged. The actual immersion time can be adjusted according to the swelling condition of the microfluidic pipeline. At the same time, in order to further facilitate the timely shedding of the microfluidic pipeline and avoid the microfluidic pipeline being immersed in the swelling solution for too long and damaging the surface morphology of the microfluidic pipeline, after the microfluidic pipeline has swelled for a certain period of time, the electric heating wire can be slightly vibrated or shaken to accelerate the shedding of the microfluidic pipeline.

[0052] S5, volatilizing the swelling solution in the swelling microfluidic channel to obtain a flexible microfluidic channel. To accelerate the volatilization speed of the swelling solution, drying or air drying can be used.

[0053] The present application also provides a flexible microfluidic pipeline preparation device, comprising a first solution pool, a second solution pool, a power module, a control module and a heating wire. The first solution pool contains a polymer precursor solution, and the second solution pool contains a swelling solution. The power module provides power to the control module. The control module is provided with at least one mechanical claw, which is clamped at one end of a heating wire, and the mechanical claw can be powered to heat the heating wire and can control the centrifugal rotation of the heating wire.

[0054] Among them, the mechanical claw of the control module controls the heating wire to partially extend into the first solution pool. The mechanical claw heats the heating wire for a period of time and then removes the heating wire from the first solution pool. The mechanical claw drives the removed heating wire to rotate centrifugally to throw out the uncured polymer precursor solution on the surface of the heating wire. Then the mechanical claw heats the heating wire for a second time to completely cure the polymer on the surface of the heating wire into a microfluidic channel. Then the mechanical claw controls the heating wire to immerse in the second solution pool, and the microfluidic channel on the surface of the heating wire swells and falls off.

[0055] In some specific embodiments, the device also includes a centrifugal chamber. After the heating wire is powered on for the first time for heating, it is moved to the centrifugal chamber by the mechanical claw and completes the centrifugal rotation process in the centrifugal chamber. The polymer precursor solution centrifugally separated is scattered in the centrifugal chamber.

[0056] In some specific embodiments, the mechanical claw can also control the electric heating wire to shake or vibrate. When the mechanical claw immerses the electric heating wire with the microfluidic pipe attached to the surface into the second solution pool, the microfluidic pipe absorbs the swelling solution. At this time, the mechanical claw controls the electric heating wire to shake or vibrate to detach the microfluidic pipe in time. It is worth noting that after the microfluidic pipe absorbs the swelling solution, when the microfluidic pipe has not completely fallen off, the mechanical claw can also control the electric heating wire to move away from the second solution pool, move the electric heating wire to the top of the collection device, and then shake or vibrate the electric heating wire to make the microfluidic pipe fall into the collection device.

[0057] In some specific embodiments, a stirring device may be provided in the first solution pool, and the stirring device can be used to configure the polymer precursor solution. At the same time, an interface corresponding to the exhaust device may be provided above the first solution pool to facilitate degassing when configuring the polymer precursor solution.

[0058] In some specific embodiments, a screen may be provided in the second solution pool, and the screen is used to hold the microfluidic pipes that have escaped from the second solution pool. The screen may be provided as a mechanical lifting structure, and when the microfluidic pipes need to be collected, the screen can be directly lifted to remove the swelling solution from all the microfluidic pipes that have fallen into the microfluidic pipes.

[0059] In some specific embodiments, the flexible microfluidic pipeline preparation device also includes: a temperature sensor for detecting the temperature of a mechanical claw, a heating wire or a first solution pool inside the device; a timer for detecting the heating time, rotation time or swelling time of the heating wire; a buzzer for alarming equipment abnormalities, such as temperature abnormalities, equipment jamming abnormalities, etc.; a liquid level meter arranged in the first solution pool and a liquid level meter arranged in the second solution pool.

[0060] According to the above-mentioned flexible microfluidic pipeline preparation method, specific embodiments and comparative examples are listed below:

[0061] In the embodiments and comparative examples, the heating wires are alloy wires, the alloy wires are iron-chromium-aluminum alloy wires, the alloy wire length is 15 cm, the alloy wire resistance is 1.4Ω / cm, the total resistance is 21Ω, and the diameter is 600μm; the polymer precursor solutions are all PDMS precursor solutions, and the PDMS precursor solution reagent is Dow Corning 184, wherein the PDMS precursor solution is configured according to a ratio of main resin to curing agent of 10:1. During the heating process of the heating wire, the heating temperature of the heating wire is mainly controlled by controlling the current size.

[0062] Embodiment 1:

[0063] S1. Prepare PDMS polymer precursor solution.

[0064] S2. Place the straight alloy wire part into the PDMS precursor solution, and heat the heating wire with electricity at a current of 2A for 45 seconds. After heating, move the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a C centrifugal manner at a rotation speed of 600 rpm for 5 seconds to obtain a heating wire with a polymer film formed on the surface.

[0065] S3. The heating wire with the polymer film formed on the surface is heated by electricity for a second time, with the current being 2A and the power-on time being 10s, to obtain the heating wire with the microfluidic channel attached to the surface.

[0066] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0067] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0068] The microfluidic pipeline was prepared as Figure 3 e, the pipe cross section is magnified at a macro scale. Figure 4 As shown ( Figure 4 I is taken with a microscope, and J is taken with a macro camera). The maximum breaking force of the PDMS flexible microfluidic channel was measured to be 0.07N. Four cross sections were measured, and the wall thickness at four relative locations on each cross section was measured. The results were all 300μm, indicating that the thickness uniformity of the microfluidic channel was good.

[0069] Embodiment 2:

[0070] S1. Prepare PDMS polymer precursor solution.

[0071] S2. Place the straight alloy wire part into the PDMS precursor solution, and heat the heating wire with electricity at a current of 2A for 45 seconds. After heating, move the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a centrifugal manner at a rotation speed of 600 rpm for 5 seconds to obtain a heating wire with a polymer film formed on the surface.

[0072] S3. The heating wire with the polymer film formed on the surface is heated by electricity for a second time, with the current being 2A and the power-on time being 20s, to obtain the heating wire with the microfluidic channel attached to the surface.

[0073] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0074] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0075] The microfluidic pipeline was prepared as Figure 3 As shown in Fig. f, the maximum breaking force of the PDMS flexible microfluidic channel was measured to be 0.07N. Four cross sections were measured, and the wall thickness at four relative locations on each cross section was measured. The results were all 300μm, indicating that the thickness uniformity of the microfluidic channel was good.

[0076] Embodiment 3:

[0077] S1. Prepare PDMS polymer precursor solution.

[0078] S2. Place the alloy wire portion having a curvature of 0.065 into the PDMS precursor solution, and heat the heating wire with an electric current of 2A for 45 seconds. After heating, move the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a centrifugal manner at a rotation speed of 600 rpm for 5 seconds to obtain a heating wire with a polymer film formed on the surface.

[0079] S3. The heating wire with the polymer film formed on the surface is heated by electricity for a second time, with the current being 2A and the power-on time being 10s, to obtain the heating wire with the microfluidic channel attached to the surface.

[0080] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0081] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0082] According to the measurement, the wall thickness of the PDMS flexible microfluidic channel is 300 μm and the maximum breaking force is 0.07N.

[0083] Embodiment 4:

[0084] S1. Prepare PDMS polymer precursor solution.

[0085] S2. Place the straight alloy wire part into the PDMS precursor solution, and heat the heating wire with a total resistance value of 30Ω, with a current of 2A and a power-on time of 45s. After heating, move the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a centrifugal manner, with a rotation speed of 600rpm and a rotation time of 5s to obtain a heating wire with a polymer film formed on the surface.

[0086] S3. The heating wire with the polymer film formed on the surface is heated by electricity for a second time, with the current being 2A and the power-on time being 10s, to obtain the heating wire with the microfluidic channel attached to the surface.

[0087] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0088] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0089] The microfluidic pipeline was prepared as Figure 3 As shown in g, the wall thickness of the PDMS flexible microfluidic channel was measured to be 350 μm and the maximum breaking force was 0.07N.

[0090] Comparative Example 1:

[0091] S1. Prepare PDMS polymer precursor solution.

[0092] S2. Place the straight alloy wire part into the PDMS precursor solution, and heat the heating wire with electricity at a current of 1A for 45 seconds. After heating, move the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a C centrifugal manner at a rotation speed of 600 rpm for 5 seconds to obtain a heating wire with a polymer film formed on the surface.

[0093] S3. The heating wire with the polymer film formed on the surface is heated for a second time with a current of 1A and a power-on time of 10s to obtain the heating wire with the microfluidic channel attached to the surface.

[0094] In this comparative example, due to the current size during the heating process, the temperature of the alloy wire after heating is too low, and the PDMS cannot be cured and attached to the surface of the alloy wire.

[0095] Comparative Example 2:

[0096] S1. Prepare PDMS polymer precursor solution.

[0097] S2. Place the straight alloy wire part into the PDMS precursor solution, and heat the heating wire with electricity at a voltage of 3A for 45 seconds. After heating, move the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a C centrifugal manner at a rotation speed of 600 rpm for 5 seconds to obtain a heating wire with a polymer film formed on the surface.

[0098] S3. The heating wire with the polymer film formed on the surface is heated by electricity for a second time, with the current being 2A and the power-on time being 20s, to obtain the heating wire with the microfluidic channel attached to the surface.

[0099] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0100] S5. Allow the swollen microfluidic channel to air dry for 5 minutes to obtain a flexible microfluidic channel.

[0101] The PDMS flexible microfluidic channel prepared in Comparative Example 2 had a wall thickness of 800 μm and a maximum breaking force of 0.5 N. The breaking force was too large and the microfluidic channel could not be used for biosensors.

[0102] Comparative Example 3:

[0103] S1. Prepare PDMS polymer precursor solution.

[0104] S2, partially placing the alloy wire in the PDMS precursor solution, heating the heating wire with an electric current of 2A and an electric current of 25s. After heating, the heating wire is kept away from the polymer precursor solution, and the heating wire is centrifugally rotated in a c centrifugal manner with a rotation speed of 600rpm and a rotation time of 5s to obtain a heating wire with a polymer film formed on the surface.

[0105] S3. The heating wire with the polymer film formed on the surface is heated by electricity for a second time, with the current being 2A and the power-on time being 20s, to obtain the heating wire with the microfluidic channel attached to the surface.

[0106] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0107] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0108] like Figure 5 As shown, in Comparative Example 3, the first heating time was too short, only 25 seconds, and the pipe wall was thin and uneven. The pipe was cut into three parts, and the wall thickness data of the two cross sections K and L were measured. The maximum thickness was 100 μm and the minimum was 10 μm.

[0109] Comparative Example 4:

[0110] S1. Prepare PDMS polymer precursor solution.

[0111] S2, partially placing the alloy wire in the PDMS precursor solution, heating the heating wire with an electric current of 2A and an electric current of 45s. After heating, the heating wire is kept away from the polymer precursor solution, and the heating wire is centrifugally rotated in a c centrifugal manner with a rotation speed of 600rpm and a rotation time of 5s to obtain a heating wire with a polymer film formed on the surface.

[0112] S3. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off, thereby obtaining a swollen microfluidic channel.

[0113] S4. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0114] like Figure 3 As shown in FIG. 4 , in comparative example 4, no secondary heating was performed, and the polymer initially solidified on the surface of the heating wire was partially dissolved by the swelling solution during the swelling and detachment process, and shrunk and collapsed after air drying, and a microfluidic channel with a complete morphology could not be obtained.

[0115] Comparative Example 5:

[0116] S1. Prepare PDMS polymer precursor solution.

[0117] S2. Place the alloy wire part in the PDMS precursor solution, and heat the heating wire with electricity at a voltage of 2.8V for 45 seconds. After heating, keep the heating wire away from the polymer precursor solution, and centrifuge the heating wire in a C centrifugal manner at a rotation speed of 600rpm for 5 seconds to obtain a heating wire with a polymer film formed on the surface.

[0118] S3. The heating wire with the polymer film formed on the surface is heated for a second time with the voltage of 2.8 V and the duration of 45 seconds to obtain the heating wire with the microfluidic channel attached to the surface.

[0119] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 30 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0120] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0121] like Figure 6As shown, the PDMS flexible microfluidic channel prepared in Comparative Example 5 was soaked in the swelling solution for too long, and the channel turned white when it was taken out. After air-drying, the outer surface of the channel was rough and frosted, and the channel shape was twisted and rugged, and it was impossible to obtain a straight or preset PDMS microfluidic channel with curvature.

[0122] Comparative Example 6:

[0123] S1. Prepare PDMS polymer precursor solution.

[0124] S2, partially placing the alloy wire in the PDMS precursor solution, heating the heating wire with an electric current of 2A and a power-on time of 45 seconds. After heating, the heating wire is moved away from the polymer precursor solution to obtain a heating wire with a polymer film formed on the surface.

[0125] S3. The heating wire with the polymer film formed on the surface is heated for a second time with a current of 2A and a power-on time of 45s to obtain the heating wire with the microfluidic channel attached to the surface.

[0126] S4. Immerse the heating wire with the microfluidic channel attached to the surface into a dichloromethane swelling solution for 5 minutes, and the microfluidic channel swells and falls off to obtain a swollen microfluidic channel.

[0127] S5. Allow the swollen microfluidic channel to air dry for 30 minutes to obtain a flexible microfluidic channel.

[0128] Microfluidic pipelines such as Figure 3 As shown in h, the PDMS flexible microfluidic channel prepared in Comparative Example 6 did not undergo a centrifugal process, and the heating wire was removed from the PDMS precursor solution after the first heating. During the second vertical downward heating process, the PDMS precursor attached and suspended on the surface gathered at the end due to gravity. After thermal curing, it appeared as an uneven channel with increasing thickness. In addition, due to the uneven thickness, the swelling rates of areas of different thicknesses were different during the swelling and immersion process, and it was difficult for the microfluidic channel to swell and separate from the heating wire.

[0129] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for preparing a flexible microfluidic pipeline based on in-situ electric heating, characterized in that: The following steps are involved: S1, preparing a polymer precursor solution, wherein the polymer precursor solution is thermally cured to form a flexible microfluidic channel, and the thermal curing temperature is 60-150° C.; S2, placing the heating wire part into the polymer precursor solution, heating the heating wire for the first time by energizing, and after heating, moving the heating wire away from the polymer precursor solution, centrifugally rotating the heating wire, and obtaining the heating wire with a polymer film formed on the surface; The centrifugal rotation axis of the heating wire is an axis in the vertical direction of the circular cross section or an axis in the extending direction of the circular cross section; S3, heating the heating wire with the polymer film formed on the surface for a second time to obtain the heating wire with the microfluidic channel attached to the surface; S4, immersing the heating wire with the microfluidic pipeline attached to the surface into a swelling solution, the microfluidic pipeline swells and separates from the heating wire, and a swollen microfluidic pipeline is obtained, and the swelling solution has a swelling effect on the microfluidic pipeline; S5. After the swelling solution in the swollen microfluidic channel is volatilized, a flexible microfluidic channel is obtained.

2. The preparation method according to claim 1, characterized in that: The heating wire is an alloy wire, and the resistance of the alloy wire is 1-10Ω / cm; in step S2, during the first power-on heating process, the power-on voltage is 0.1-0.3V / cm, and the power-on time is 30-60s.

3. The preparation method according to claim 1, characterized in that: In step S2, when the electric heating wire is centrifugally rotated, the rotation speed is 500-1500 rpm and the rotation time is 3-10 s.

4. The preparation method according to claim 2, characterized in that: In step S3, during the second heating process, the voltage is 0.1 to 0.3 V / cm, and the time is 10 to 45 seconds.

5. The preparation method according to claim 1, characterized in that: The polymer precursor solution is selected from any one of a PDMS precursor solution, a PBAT precursor solution, a polyimide precursor solution, a thermoplastic elastomer, and a PVA precursor solution.

6. The preparation method according to claim 5, characterized in that: The swelling solution is selected from any one of dichloromethane, chloroform, DMF, toluene, isopropanol and n-hexane.

7. The preparation method according to claim 1, characterized in that: In the step S4, the heating wire with the microfluidic conduits uniformly attached to the surface is immersed in the swelling solution for 1 to 10 minutes.

8. A microfluidic channel prepared by the preparation method according to any one of claims 1 to 7.

9. A microfluidic channel preparation device used in the preparation method according to any one of claims 1 to 7, characterized in that: It includes a first solution tank, a second solution tank, a power module, a control module and a heating wire; The first solution pool contains a polymer precursor solution, and the second solution pool contains a swelling solution; the power module is connected to a control module, and the control module is used to heat at least one of the heating wires and clamp at least one of the heating wires to operate in the first solution pool, in the second solution pool, or in an area outside the first solution pool and the second solution pool; The action at least includes moving and rotating around the central axis in the vertical direction of the circular cross section of the heating wire.

10. The microfluidic channel preparation device according to claim 9, characterized in that: The method further comprises at least one of the following devices: a temperature sensor, a timer, a buzzer, a liquid level meter arranged in the first solution pool, and a liquid level meter arranged in the second solution pool.

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