Programmable light-induced gradient wetting micro-fluidic chip

Abstract

The programmable light-induced gradient wetting micro-fluidic chip comprises an upper polar plate and a lower polar plate, the upper polar plate comprises conductive glass and a first hydrophobic layer, the lower polar plate comprises a second hydrophobic layer, a dielectric layer and monocrystalline silicon, a bias power supply is connected between the upper polar plate and the lower polar plate, and liquid drops are arranged between the upper polar plate and the lower polar plate. A projector is arranged above the upper pole plate and emits a light source, the light source meets the requirement that after the projector projects the light source on the monocrystalline silicon, a virtual electrode is formed in a partial area on the lower pole plate, the virtual electrode is a graph with gray gradient, and liquid drops intersect with the virtual electrode. Compared with the prior art, the method has the advantages of programmable path, selective operation, accurate operation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of light-induced gradient wetting, and particularly to a programmable light-induced gradient wetting microfluidic chip. Background Art

[0002] Microfluidic chips have broad application prospects in fields such as biomedicine and chemical detection. The objects processed by microfluidic chips are droplets. When long-distance movement of droplets is involved, an engineered surface with gradient wetting is usually used to achieve the transportation of droplets. Gradient wetting surfaces can be divided into two types, physical and chemical, according to different preparation principles. However, these gradient wetting surfaces generally face problems such as cumbersome manufacturing, difficult sample transfer, uncontrollable speed, and single moving direction, which greatly limit their application scope.

[0003] Electrowetting on Dielectric (EWOD) technology, as the most common digital microfluidic technology in the lab-on-a-chip, can achieve precise manipulation of droplets, such as movement, merging, and splitting, by virtue of its advantages of non-contact, high-throughput, and high-precision operation. However, when dealing with high-throughput and long-distance moving droplets, EWOD technology faces challenges such as complex wiring and limited space due to its dependence on pixelated electrode wiring. To address these limitations, Opto-Electrowetting (OEW) technology provides a new solution. Opto-Electrowetting (OEW) technology generates virtual electrodes by projecting light with different intensities onto a photoconductive material, avoiding complex electrode wiring, having the ability to flexibly manipulate droplets, and simplifying system design. However, there is still room for optimization in terms of the accuracy of droplet transmission, operation efficiency, and throughput of OEW technology. Summary of the Invention

[0004] The purpose of the present invention is to provide a programmable light-induced gradient wetting microfluidic chip to overcome the problems of low accuracy and poor flexibility in droplet transmission of OEW technology.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A programmable light-induced gradient wetting microfluidic chip includes an upper electrode plate and a lower electrode plate. The upper electrode plate includes conductive glass and a first hydrophobic layer. The lower electrode plate includes a second hydrophobic layer, a dielectric layer, and a single crystal silicon. A bias power supply is connected between the upper electrode plate and the lower electrode plate. A droplet is arranged between the upper electrode plate and the lower electrode plate. A projector is provided above the upper electrode plate, and the projector emits a light source. The light source satisfies that after the projector projects it onto the single crystal silicon, virtual electrodes are formed in some areas on the lower electrode plate. The virtual electrodes are patterns with a gray-scale gradient, and the droplet intersects with the virtual electrodes.

[0007] Further, taking the length of the upper plate and the lower plate as the Y-axis direction, the width of the upper plate and the lower plate as the X-axis direction, and the height of the upper plate and the lower plate as the Z-axis direction, the light intensity of the virtual electrode is distributed in a gradient along the Y-axis direction in the positive Y-axis direction, and the light intensity in the positive direction is always greater than that in the negative direction.

[0008] Further, the droplet intersects with the virtual electrode to form four focal points, namely points A, B, C, and D, where the Y-axis coordinates of points A and B are both greater than those of points C and D.

[0009] Further, the contact angle on the AB line formed by points A and B is smaller than the contact angle on the CD line formed by points C and D.

[0010] Further, the virtual electrode is an electrodeless electrode or a polar electrode.

[0011] Further, the light intensity of the electrodeless electrode changes continuously along the positive Y-axis direction.

[0012] Further, the polar electrode is divided into several regions, and the light intensity of any region is greater than that in the adjacent region in the negative Y-axis direction.

[0013] Further, the length of the region in the polar electrode in the Y-axis direction is less than or equal to the diameter of the droplet.

[0014] Further, the part of the lower plate except for some regions is other regions, and the other regions are regions without light irradiation.

[0015] Further, a gasket is also provided between the upper plate and the lower plate.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] By projecting light with an intensity gradient on a plane, the present invention makes the wettability of the irradiated surface generate a gradient, thereby controlling the transportation of the droplet on the plane. Since the intensity gradient value, area, and gradient direction of the light source with an intensity gradient can be adjusted, programmable transportation of the droplet can be achieved. The present invention has the advantages of programmable path, selective operation, and precise operation, rich functions and strong flexibility, and is suitable for various microfluidic application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram when the present invention is working;

[0019] Figure 2 It is a structural diagram of the present invention;

[0020] Figure 3 It is a schematic diagram of projecting a light source with an intensity gradient onto a droplet;

[0021] Figure 4 Schematic diagram of non-polar electrode and polar electrode;

[0022] In the figure, there are upper plate 300, lower plate 600, conductive glass 301, first hydrophobic layer 302, second hydrophobic layer 601, dielectric layer 602, single crystal silicon 603, bias power supply 700, droplet 400, projector 100, light source 200, virtual electrode 801. Non-polar electrode 80101, polar electrode 80102, gasket 500. Specific implementation mode

[0023] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0024] The present invention relates to a light-induced gradient wetting technology for realizing programmable transportation of droplets. The system projects light with an intensity gradient on a plane, so that the wettability of the irradiated surface generates a gradient, thereby controlling the transportation of droplets on the plane. Since the intensity gradient value, area, and gradient direction of the light source with an intensity gradient can be adjusted, programmable transportation of droplets can be realized. The present invention has the advantages of programmable path, selective operation, and precise operation, and is applicable to a variety of microfluidic application scenarios.

[0025] The present invention proposes a programmable light-induced gradient wetting microfluidic chip for programmable transportation of droplets, and realizes programmable gradient wetting on the surface of the chip by adjusting the direction, area, and size of the intensity gradient of light, and further realizes programmable operation of droplets.

[0026] A programmable light-induced gradient wetting microfluidic chip of the present invention includes an upper plate 300 and a lower plate 600. The upper plate 300 includes a conductive glass 301 and a first hydrophobic layer 302. The lower plate 600 includes a second hydrophobic layer 601, a dielectric layer 602, and a single crystal silicon 603. A bias power supply 700 is connected between the upper plate 300 and the lower plate 600. A droplet 400 is arranged between the upper plate 300 and the lower plate 600. A projector 100 is arranged above the upper plate 300. The projector 100 emits a light source 200. After the light source 200 is projected by the projector 100 on the single crystal silicon 603, a virtual electrode 801 is formed in a part of the area on the lower plate 600. The virtual electrode 801 is a pattern with a gray scale gradient, and the droplet 400 intersects with the virtual electrode 801. The schematic diagram of the present invention during operation is as Figure 1 shown, and the structural diagram is as Figure 2 shown.

[0027] The programmable light-induced gradient wetting microfluidic chip consists of the following parts:

[0028] The chip consists of an upper electrode plate 300 and a lower electrode plate 600. The upper electrode plate 300 is composed of a conductive glass 301 and a hydrophobic layer 302, while the lower electrode plate consists of a hydrophobic layer 601, a dielectric layer 602, and a single crystal silicon 603. A spacer 500 is used to place between the upper and lower electrode plates to ensure the spacing. The droplet 400 is located between the electrode plates, and a bias power supply 700 is connected between the upper electrode plate 300 and the lower electrode plate 600. Based on the principle of electro-wetting on dielectric, the present invention designs a programmable photo-induced gradient wetting microfluidic chip for realizing programmable operations of droplets on the microfluidic chip. The basic working principle of the system is as follows: When light with different intensities irradiates on the surface of the single crystal silicon 603, its conductivity changes, forming different electro-wetting effects. After applying the bias power supply 700, potential differences are generated in regions with different conductivities, which leads to changes in the wetting characteristics of the hydrophobic surface 601. According to the classical Lippmann-Young equation, the contact angle in the region with a higher potential is smaller, and the difference in contact angles causes the droplet to move.

[0029] In specific implementation, such as Figure 3 , the projector 100 is used to project a light source with an intensity gradient to irradiate a specific area called the virtual driving electrode 801. The light intensity on the virtual electrode 801 is distributed in a gradient along the Y-axis direction, and the light intensity in the positive direction is always greater than that in the negative direction, while other regions 802 are not irradiated. For the droplet within the driving electrode region, its contact angle on the AB line is always smaller than that on the CD line. The continuous difference in contact angles drives the droplet to move towards the side with a smaller contact angle, that is, the positive direction of the Y-axis. Among them, the change in the light intensity gradient can be achieved in two ways, which are respectively called the non-polar electrode 80101 and the polar electrode 80102. Among them, the non-polar electrode 80101 means that the light intensity on the virtual electrode 801 changes continuously along the positive direction of the Y-axis. The polar electrode 80102 means that the virtual electrode 801 is divided into several regions, and the light intensity in the positive direction of the Y-axis is always greater than that in the adjacent negative direction region. Different from the non-polar electrode 80101, the diameter of the droplet is greater than or equal to the length of each region of the polar electrode 80102 in the Y-axis direction. Schematic diagrams of the non-polar electrode and the polar electrode are as Figure 4 shown.

[0030] To achieve the above effects, the formation of the virtual electrode 801 is essentially by the projector projecting a pattern with a gray scale gradient onto the single crystal silicon 603. The pattern with the gray scale gradient forms the virtual electrode 801, and other regions 802 remain black, that is, regions without light irradiation.

[0031] In practical applications, a high-resolution camera is used to collect the position coordinates of the droplet in real time. According to the requirements, the starting position, target position, and required moving speed of the droplet can be determined, so as to calculate the gray scale gradient, direction, and intensity values of the projected pattern required.

[0032] The preparation process of the present invention is as follows:

[0033] 1. Place the purchased single-crystal silicon substrate 603 in acetone, isopropyl alcohol, and deionized water solution in sequence and ultrasonically clean for 5 minutes. Then use a nitrogen gun to dry the surface of the substrate, and dry it on a hot plate at 100°C for 5 minutes.

[0034] 2. Spin-coat the SU8 dielectric layer 602 using a spin coater at a rotation speed of 3000 rpm for 1 minute. After spin-coating, dry it on a hot plate at 100°C, then heat it up to 150°C and dry for 30 minutes, and finally cool it naturally.

[0035] 3. Spin-coat the Teflon hydrophobic layer 601 using a spin coater at a rotation speed of 3000 rpm for 1 minute. After spin-coating, dry it on a hot plate at 100°C, and finally cool it naturally.

[0036] 4. Peel the film of the purchased ITO glass 301, and spin-coat the Teflon hydrophobic layer 302 using a spin coater at a rotation speed of 3000 rpm for 1 minute. After spin-coating, dry it on a hot plate at 100°C, and finally cool it naturally to be used as the upper electrode plate.

[0037] 5. Add an appropriate amount of liquid droplets 400 between the two electrode plates, project the gradient virtual electrode 801 above with a projector, and apply an alternating current of 350 VPP and 1 KHz to the bottom end of the ITO glass and the upper surface of the single-crystal silicon to make the liquid droplets move along the gradient direction.

[0038] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A programmable light-induced gradient wetting microfluidic chip, characterized in that: The invention comprises an upper plate (300) and a lower plate (600), wherein the upper plate (300) comprises a conductive glass (301) and a first hydrophobic layer (302), and the lower plate (600) comprises a second hydrophobic layer (601), a dielectric layer (602) and single crystal silicon (603), a bias power supply (700) is connected between the upper plate (300) and the lower plate (600), and a liquid droplet (4 00), a projector (100) is arranged above the upper electrode plate (300), the projector (100) emits a light source (200), and the light source (200) satisfies the projector (100) to project it onto the single crystal silicon (603), and a partial area on the lower electrode plate (600) forms a virtual electrode (801), the virtual electrode (801) is a pattern with a grayscale gradient, and the droplet (400) intersects with the virtual electrode (801).

2. A programmable light-induced gradient wetting microfluidic chip according to claim 1, characterized in that: The length of the upper electrode plate (300) and the lower electrode plate (600) is in the Y-axis direction, the width of the upper electrode plate (300) and the lower electrode plate (600) is in the X-axis direction, and the height of the upper electrode plate (300) and the lower electrode plate (600) is in the Z-axis direction. The light intensity of the virtual electrode (801) is distributed in a gradient along the positive direction of the Y-axis, and the light intensity in the positive direction is always greater than that in the negative direction.

3. A programmable light-induced gradient wetting microfluidic chip according to claim 2, characterized in that: The droplet (400) intersects with the virtual electrode (801) to form four focal points, namely points A, B, C and D, wherein the Y-axis coordinates of points A and B are greater than the Y-axis coordinates of points C and D.

4. The programmable light-induced gradient wetting microfluidic chip according to claim 3, characterized in that: The contact angle on the line AB formed by points A and B is smaller than the contact angle on the line CD formed by points C and D.

5. The programmable light-induced gradient wetting microfluidic chip according to claim 4, characterized in that: The virtual electrode (801) is a non-polar electrode (80101) or a polar electrode (80102).

6. The programmable light-induced gradient wetting microfluidic chip according to claim 5, characterized in that: The light intensity of the non-polar electrode (80101) changes continuously along the positive direction of the Y axis.

7. The programmable light-induced gradient wetting microfluidic chip according to claim 6, characterized in that: The polarized electrode (80102) is divided into a plurality of regions, and the light intensity in any region is greater than the light intensity in the adjacent region in the negative direction of the Y axis.

8. The programmable light-induced gradient wetting microfluidic chip according to claim 7, characterized in that: The length of the area in the polar electrode (80102) in the Y-axis direction is less than or equal to the diameter of the droplet (400).

9. The programmable light-induced gradient wetting microfluidic chip according to claim 1, characterized in that: The portion other than the partial area on the lower electrode plate (600) is the other area (802), and the other area (802) is a non-light irradiated area.

10. The programmable light-induced gradient wetting microfluidic chip according to claim 1, characterized in that: A gasket (500) is also provided between the upper electrode plate (300) and the lower electrode plate (600).

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