A method for laser cutting water and its application in processing microfluidic chips

Abstract

The present invention discloses a method for laser cutting water and its application in processing microfluidic chips: coating the surface of a solid substrate with hydrophobic SiO2 nano-sol; dropping water onto the solid substrate so that the hydrophobic SiO2 nanoparticles on the surface of the solid substrate wrap around the water surface; sucking out part of the water wrapped by the hydrophobic SiO2 nanoparticles to form a liquid cake for laser cutting. By using a laser to cut the liquid cake according to the profile of the fluid channel, a microfluidic chip fluid channel maintained by hydrophobic SiO2 nanoparticles and the water encapsulated therein can be obtained. The present invention makes the processing of microfluidic chips have the advantages of simple operation, high speed and low cost, and the processed microfluidic chips have the characteristics of openness, air permeability and light transmittance, and can be used as platforms for biochemical sensing, chemical synthesis and cell culture.

Description

Technical Field

[0001] The invention relates to microfluidic chip processing in the engineering field, and in particular to a method for laser cutting water and a microfluidic chip processed by the method. Background Art

[0002] Microfluidics is a technology that controls the flow of trace amounts of liquid within a microfluidic chip. Due to its advantages such as miniaturization, high throughput, functional integration, and low sample consumption, microfluidics has received widespread attention in the fields of chemistry, biology, and materials. Silicon-based materials (glass, silicon wafers) and polymer materials (PDMS, PMMA) are the main substrate materials in microfluidic chip processing. The processing of silicon-based materials mainly includes photolithography and wet etching. The processing of polymer materials includes molding, hot pressing, laser etching, and soft lithography. Based on these methods, the substrate material can be used to process fluid channels and pump and valve structures for liquid manipulation.

[0003] Although microfluidic chips based on silicon-based materials and polymer materials have high precision, the processing process is cumbersome. In addition, since microfluidic chips are usually disposable, new microfluidic chips need to be processed using substrate materials as the experiment progresses, resulting in high material and manufacturing costs (especially when using photolithography, wet etching, and laser etching methods, it is generally necessary to use multiple substrate materials to process fluid channels with functional units such as sample addition and sampling). Therefore, it is necessary to develop open microfluidic chips that do not require processing of solid channel structures.

[0004] Chinese patent CN110511265A discloses an isoelectric focusing device based on liquid marbles. By shaping the liquid marbles, a columnar separation channel with acid and alkaline solution pools at both ends is formed. However, the liquid in the channel needs to be pre-loaded in the form of liquid marbles, which is not suitable for use as a microfluidic chip. There are also studies reporting the use of metal wires at the end of the track to split the liquid marbles falling along the track. There are no reports of using laser cutting technology to cut water to process open microfluidic chips. Summary of the invention

[0005] The purpose of the present invention is to provide a method for laser cutting water and its application in processing microfluidic chips, so as to solve the problems of complicated operation and high material consumption of traditional microfluidic chip processing technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A water method for laser cutting, the method comprising the following steps:

[0008] 1) preparing a modified mixture consisting of micro-nano particles and water or an aqueous solution, wherein the micro-nano particles in the modified mixture are wrapped on the surface of the water or the aqueous solution;

[0009] 2) removing part of the water or aqueous solution in the modified mixture to obtain a base material that can be cut by laser, wherein the base material forms a cut (or cut mark) at the cutting position during laser cutting, which is separated by the micro-nano particles at the cutting position and / or the periphery of the cutting position and does not contain base material components.

[0010] Preferably, step 1 specifically includes the following steps: coating a hydrophobic SiO2 nanosol on the flat surface of a solid-phase substrate (the substrate is made of plastic, metal, etc.), loading water or an aqueous solution on the coating after the sol is dried to form a hydrophobic SiO2 nanoparticle coating, and then shaking the solid-phase substrate to make the loaded water or aqueous solution roll on the surface of the coating until it is wrapped by the hydrophobic SiO2 nanoparticles to form a liquid cake (that is, the water or aqueous solution is wrapped by the hydrophobic SiO2 nanoparticles to form a liquid cake, thereby changing the wettability of the water or aqueous solution on the surface of the solid-phase substrate).

[0011] Preferably, the step 2 specifically includes the following steps: extracting water or aqueous solution from the liquid cake at a ratio of removing 80% to 95% of the volume of the water or aqueous solution wrapped by the hydrophobic SiO2 nanoparticles (by removing a portion of the water or aqueous solution wrapped by the hydrophobic SiO2 nanoparticles, the liquid cake obtained in step 1 changes from transparent to translucent and becomes thinner. This thin liquid cake can not only maintain the wrapping of the water or aqueous solution by the hydrophobic SiO2 nanoparticles, but also enhance the light transmittance of the liquid cake by injecting liquids such as aqueous solutions and colloids into the liquid cake at any position of the liquid cake, and can also show cuttability under the action of laser, that is, forming separated liquid cake areas on both sides of the slit during laser cutting, and as the slit forms a closed pattern, two independent liquid cakes are formed inside and outside the slit, thereby combining the air permeability of the liquid cake itself, so that the liquid cake after the water or aqueous solution is extracted in step 2 can be used as a base material for laser cutting, which takes into account air permeability, light permeability and openness).

[0012] Preferably, after step 2, the thickness of the liquid cake is 0.1 mm to 1.0 mm.

[0013] Preferably, the method further comprises the following steps: laser cutting is performed on the substrate material according to the designed pattern (e.g., a graphic element with an arbitrary contour shape contained in a picture, text, microfluidic chip, etc.; for a microfluidic chip, the pattern is mainly reflected by its channel structure) (also cutting the designed pattern on the liquid cake after extracting water or an aqueous solution); the laser power of the laser cutting process is 7.0w-15.0w, and the laser cutting speed is 1.0mm / s-50.0mm / s. The formation of the slit in the method of laser cutting water mainly utilizes the evaporation of water by the laser and the fluidity of micro-nano particles (e.g., hydrophobic SiO2 nanoparticles) on the water surface. Therefore, when the laser power is too low or the cutting speed is too slow, the water cannot be cut because the slit cannot be formed. When the laser power is too high or the cutting speed is too fast, the slit will be too wide, resulting in poor processing accuracy of patterned water formed by laser cutting.

[0014] Preferably, the method also includes the following steps: using a mechanical tool (such as a knife) to cut off the water or aqueous solution in the pattern area corresponding to the base material formed by laser cutting (based on the micro-nanoparticles introduced at the isolation position by cutting), or adding water or aqueous solution at the isolation position to restore the internal connectivity of the pattern area.

[0015] An open microfluidic chip comprises a channel structure maintained by micro-nano particles and water or aqueous solution wrapped by the micro-nano particles, formed by laser cutting the channel contour on the base material according to a designed pattern using the above-mentioned base material.

[0016] Preferably, the channel structure of the chip is selected from one (single channel) or a combination of multiple (such as cross-complex, splicing, array of multiple channels of the same or different types) of linear channels and curved channels arranged on a solid phase substrate.

[0017] Preferably, the thickness of the channel structure is 0.1 mm to 1.0 mm, and the width of a single channel in the channel structure is 0.5 mm to 10 mm.

[0018] The beneficial effects of the present invention are embodied in:

[0019] The present invention obtains a base material by removing (e.g. extracting) a portion of water or aqueous solution from water or aqueous solution wrapped by micro-nano particles (e.g. hydrophobic SiO2 nanoparticles), and laser cutting technology can be used to process water of various shapes on the base material (the shape of the water after processing is maintained by the water or aqueous solution in the patterned area of ​​the corresponding shape and the micro-nano particles wrapping this portion of water or aqueous solution), so that the laser cutting method of water proposed in the present invention can be used for simple, fast and low-cost processing of microfluidic chips.

[0020] Furthermore, the present invention controls the ratio of the extracted water or aqueous solution (the ratio affects the thickness of the liquid cake after extraction) so that the base material can take into account the air permeability, light transmittance and openness after laser cutting.

[0021] The microfluidic chip of the present invention has a channel structure processed by the above-mentioned substrate material, which can be obtained directly by laser cutting after the substrate material is prepared on the solid phase substrate, and can maintain different shapes of the channel structure (for example, composed of water or aqueous solution and hydrophobic SiO2 nanoparticles encapsulating the water or aqueous solution) on the plane provided by the solid phase substrate, without processing patterned solid channels, and at the same time, the channel structure of the microfluidic chip can continue to inject liquid (injection of a single liquid can be achieved from any position of the channel structure of the microfluidic chip, and multi-point mixed injection of different liquids can be achieved) and extract liquid, that is, it has good openness, and the channel structure has good light transmittance after the liquid is injected. The microfluidic chip of the present invention can be used as a platform for biochemical sensing, chemical synthesis and cell culture. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of laser cutting water.

[0023] Figure 2 This is a dynamic diagram of laser cutting water (the cuts formed at four different time points during the laser cutting process: 3 seconds, 6 seconds, 9 seconds and 12 seconds).

[0024] Figure 3 The pictures (a, b) and text (c) are processed on the liquid cake after water is extracted using laser cutting and liquid injection.

[0025] Figure 4 Microfluidic chips with different structures (a, c, d, e, f) processed on the liquid cake after water extraction by laser cutting and the processing accuracy measurement (b).

[0026] Figure 5 Results of liquid manipulation based on the fabricated microfluidic chip (a: injection of three different liquids; b, c, d, e: injection of two different liquids).

[0027] Figure 6 Schematic diagram of metal ion detection using the processed microfluidic chip.

[0028] Figure 7 Schematic diagram of the closing and opening operations of the valve structure in the microfluidic chip (1, 2, and 3 represent the sequence of each operation). DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments are only used to explain the present invention but not to limit the protection scope of the present invention.

[0030] (I) Operation process of laser cutting water

[0031] like Figure 1 As shown, first, pour the hydrophobic SiO2 sol into a plastic culture dish and cover the inner surface of the culture dish (referring to the bottom and sides, but not filling the culture dish). After the poured hydrophobic SiO2 sol is naturally dried, several layers of hydrophobic SiO2 nanoparticles will remain on the inner surface of the culture dish. After water is dripped into the inside of the culture dish and the culture dish is shaken, the hydrophobic SiO2 nanoparticles will be wrapped on the surface of the water. Then, use a syringe to extract 95% (v / v) of the water wrapped by the hydrophobic SiO2 nanoparticles to form a thin liquid cake. Finally, use a laser cutting machine to cut the designed pattern on the liquid cake.

[0032] In order to achieve the purpose of laser cutting water, before starting the laser cutting process, the parameters of the laser emitted by the laser head of the laser cutting machine are set, for example, the laser power is 10w, and the laser cutting speed (i.e. the scanning speed of the laser head) is 10.0mm / s; then through continuous laser scanning, an independent liquid cake located in the area surrounded by the cut mark is finally cut out, that is, a complete liquid cake is cut into two parts (see Figure 2 After 12 seconds, a liquid cake approximately in the shape of a dumbbell was cut out from a liquid cake having a thickness of about 0.1 mm).

[0033] (ii) Using laser cutting to process patterned water and continue to inject liquid

[0034] First, the laser cutting water operation process is used to process water with different patterns that form the Tai Chi diagram, water with different patterns that form the image of a panda, and water with stroke patterns that form characters (there can be no inclusion relationship between the patterns, or a large pattern can contain a small pattern). Figure 3 As shown in (a) and 3(b), based on the openness of the water after patterning (i.e., the corresponding pattern area is composed of water and hydrophobic SiO2 nanoparticles that wrap water, and the thickness is relatively thin, so liquid can continue to be injected into the pattern area and the overall outline of the pattern area remains unchanged), milk (white) and ink (black) are injected into different areas of the processed water by syringes (pressure is provided by a micro-injection pump to drive the syringe). Figure 3 As shown in (c), the aqueous solution containing the pigment is injected into each area of ​​the processed text-shaped water (i.e., the stroke pattern area). This proves that liquids of different compositions can be injected into the patterned water.

[0035] (III) Using laser cutting to process microfluidic chips with complex channels

[0036] The laser cutting process is used to process microfluidic chips with different structures. Figure 4 As shown in (a), the microfluidic chip has a cross-shaped fluid channel, which contains a straight channel and an approximately circular injection area and reaction pool. This fluid channel can be obtained by laser cutting in one process, and the processing accuracy of the straight channel reaches 1mm. Figure 4 (b). Figure 4 (c) Figure 4 As shown in (e), microfluidic chips containing curved channels and spiral microfluidic chips can be obtained by one-time laser cutting. Figure 4 (d) Figure 4 (f) The array-type microfluidic chip and the dispersed microfluidic chip shown can also be obtained by laser cutting in one process, which proves that the above laser cutting method has the ability to process microfluidic chips with complex channel structures.

[0037] It should be noted that in order to more clearly display the structure of the microfluidic chip within the cut (specifically, the fluid channel within the closed area surrounded by the cut), after the laser cutting of the liquid cake was completed, an aqueous solution containing a pigment was injected into the microfluidic chip with a syringe.

[0038] 4. Manipulating liquids in microfluidic chips

[0039] By using a microfluidic chip with fluid channels and a microinjection pump to drive a syringe, sufficient amount of liquid is injected into the fluid channel at different selected positions, thereby realizing the manipulation of a variety of different liquids in the chip. Figure 5 (a) Demonstration of three liquids being injected into the chip through three dispersed injection areas of the fluid channel and then mixed in the reaction pool at the center of the fluid channel. Figure 5 (b) to Figure 5 (d) Demonstrates the mixing of the two liquids in the reaction pool on the other side of the fluid channel after different liquids are injected into two adjacent injection areas on one side of the fluid channel in three microfluidic chips with different structures. Figure 5 (e) Demonstrates the mixing of two different liquids injected at different positions in the spiral channel. This proves that the microfluidic chip processed by laser cutting water can meet the needs of various types of experiments.

[0040] (V) Metal ion detection using microfluidic chips

[0041] Based on the transparency of microfluidic chips, dispersed microfluidic chips can be used for colorimetric detection of metal ions. Figure 6 As shown, a small amount is used for Fe 3+ 、Al 3+ and Cr 6+The color reagents are injected into different reaction pools using syringes. As more samples are injected into the injection area, the samples flow into the reaction pool (while flushing back a very small amount of color reagents that have flowed out of the reaction pool) and react with the color reagents. Since the microfluidic chip is transparent at this time, the results of the color reaction can be obtained by taking pictures with a camera.

[0042] (VI) Demonstration of microfluidic chip valve function

[0043] like Figure 7 As shown, when the channel of the microfluidic chip is cut by a blade, and a micro-injection pump is used to drive a syringe to inject liquid into the microfluidic chip, the liquid cannot flow in the microfluidic chip (i.e., flow from the circular area at one end of the channel to the circular area at the other end), and the channel is disconnected by the "valve closed" function (the part connected between the cuts on both sides of the channel is blocked by the hydrophobic SiO2 nanoparticles brought in when the blade passes). When water is dripped at the disconnected position of the channel of the microfluidic chip, the micro-injection pump is used to drive the syringe, and the injected liquid can flow in the microfluidic chip, and the channel is connected by the "valve open" function.

Claims

1. A method for laser cutting water, characterized in that: The method comprises the following steps: 1) preparing a modified mixture consisting of hydrophobic micro-nano particles and water or an aqueous solution on a solid phase matrix, wherein the hydrophobic micro-nano particles in the modified mixture are wrapped on the surface of the water or the aqueous solution; 2) removing part of the water or aqueous solution in the modified mixture so that the modified mixture obtained in step 1 changes from transparent to translucent and becomes thinner, thereby obtaining a substrate material that can be cut by laser, wherein the substrate material forms a slit that does not contain substrate material components at a cutting position separated by the hydrophobic micro-nano particles at the cutting position and / or the periphery of the cutting position during laser cutting; The method further comprises the following steps: laser cutting is performed on the substrate material obtained in step 2 according to the designed pattern reflecting the channel structure of the microfluidic chip, thereby processing microfluidic chips with different structures.

2. A method for laser cutting water according to claim 1, characterized in that: The step 1 specifically includes the following steps: coating a hydrophobic SiO2 nanosol on the surface of a solid substrate, loading water or an aqueous solution on the coating after the sol is dried to form a hydrophobic SiO2 nanoparticle coating, and then shaking the solid substrate to make the loaded water or aqueous solution roll on the surface of the coating until the hydrophobic SiO2 nanoparticles wrap to form a liquid cake.

3. A method for laser cutting water according to claim 2, characterized in that: The step 2 specifically includes the following steps: extracting water or aqueous solution from the liquid cake at a ratio of removing 80% to 95% of the volume of the water or aqueous solution enclosed by the hydrophobic SiO2 nanoparticles.

4. A method for laser cutting water according to claim 2 or 3, characterized in that: After step 2, the thickness of the liquid cake is 0.1 mm ~ 1.0 mm.

5. The method for laser cutting water according to claim 1, characterized in that: The laser power of the laser cutting process is 7.0 W ~ 15.0 W, and the laser cutting speed is 1.0 mm / s ~ 50.0 mm / s.

6. A method for laser cutting water according to claim 5, characterized in that: The method further comprises the following steps: using a mechanical tool to cut off the water or aqueous solution in the pattern area corresponding to the base material formed by laser cutting, or restoring the pattern area by adding water or aqueous solution at the cut-off position.

7. A microfluidic chip, characterized in that: The chip comprises a channel structure maintained by hydrophobic micro-nano particles and water or aqueous solution wrapped by the hydrophobic micro-nano particles, formed by using an air-permeable and light-permeable open base material and laser cutting the channel profile on the base material according to a designed pattern; The base material is composed of hydrophobic micro-nano particles and water or an aqueous solution. The hydrophobic micro-nano particles are wrapped on the surface of the water or the aqueous solution. During laser cutting, the base material forms a cut that does not contain base material components at the cutting position, which is separated by the hydrophobic micro-nano particles at the position and / or the periphery of the position.

8. A microfluidic chip according to claim 7, characterized in that: The channel structure of the chip is selected from a combination of one or more linear channels and curved channels arranged on a solid phase substrate.

9. A microfluidic chip according to claim 7, characterized in that: The thickness of the channel structure is 0.1 mm to 1.0 mm, and the width of a single channel in the channel structure is 0.5 mm to 10 mm.

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