Method for generating liquid drops on biplane light-operated electrowetting device

Abstract

The invention relates to a method for generating liquid drops on a double-plane light-operated electrowetting device, which comprises the following steps of: acquiring the double-plane light-operated electrowetting device, applying bias voltage on an electrode of the device, generating a transverse electric field at the moment, capturing the outline and the position of the liquid drops, and generating a liquid drop on the double-plane light-operated electrowetting device. Two parallel dark fringes are projected above the liquid drop by using a projector according to the outline and the position, the rest part is illuminated to split the liquid drop, the dark fringes do not coincide and penetrate through the liquid drop, the direction of the dark fringes is perpendicular to the direction of an electric field of a lower polar plate of the device, and the direction of a transverse electric field is set as an X axis; the biplane light-operated electrowetting device comprises an upper polar plate and a lower polar plate, electrodes are arranged at the two ends of the lower polar plate and comprise a first electrode and a second electrode, and a plug gauge is arranged between the upper polar plate and the lower polar plate. Compared with the prior art, the device has the advantages of realizing uniform splitting of liquid drops and the like.

Description

Technical Field

[0001] The invention relates to the technical field of light-controlled electrowetting, and in particular to a method for generating droplets on a double-plane light-controlled electrowetting device. Background Art

[0002] Lab-on-a-chip has broad application prospects in the fields of biomedicine, chemical detection, etc., and has therefore been widely discussed by researchers. Electrowetting on Dielectric (EWOD) technology is the most common discrete flow digital microfluidic technology in lab-on-a-chip, because EWOD technology has the advantages of non-intervention, high throughput, and high operating precision. At present, EWOD technology has successfully realized the movement, merging and splitting of droplets with pixelated electrodes, and has been successfully applied. However, when faced with high-throughput, small-volume droplet application scenarios, EWOD faces wiring problems. Opto-Electrowetting (OEW) is expected to solve this problem. This technology uses photoconductive materials and light to realize reconfigurable virtual electrodes. The virtual electrodes can realize the two-dimensional movement of droplets on a single plane OEW. However, it is challenging to achieve controllable splitting of droplets on a single plane to produce droplets, which makes it impossible for OEW to quickly generate droplets, which greatly limits the practical application of OEW. Summary of the invention

[0003] The purpose of the present invention is to provide a method for generating droplets on a double-plane optically controlled electrowetting device in order to achieve uniform and controllable splitting of droplets.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A method for generating droplets on a dual-plane optically controlled electrowetting device, the method comprising the following steps:

[0006] Obtain a dual-plane light-controlled electrowetting device, apply a bias voltage to the electrode of the device, generate a transverse electric field, and then capture the contour and position of the droplet. Use a projector to project two parallel dark stripes above the droplet according to the contour and position, and illuminate the rest of the droplet to split the droplet. The dark stripes do not overlap and penetrate the droplet. The direction of the dark stripes is perpendicular to the electric field direction of the lower plate of the device. Assume that the direction of the transverse electric field is the X-axis, then;

[0007] The dual-plane light-controlled electrowetting device comprises an upper electrode plate and a lower electrode plate. Electrodes are arranged at two ends of the lower electrode plate. The electrodes comprise a first electrode and a second electrode. A plug gauge is arranged between the upper electrode plate and the lower electrode plate.

[0008] Furthermore, the projecting of two parallel dark stripes on the droplet using a projector according to the contour and position is specifically as follows: controlling the width of the dark stripes to be between 1 / 2 and 1.5 times the radius of the droplet, controlling the widths of the two dark stripes to be the same, controlling the width of the gap between the two dark stripes to be between 1 / 50 and 1 times the radius of the droplet, and coinciding with the midline of the gap between the two dark stripes with the midline of the droplet in the Y-axis direction, wherein the Y-axis is perpendicular to the X-axis.

[0009] Furthermore, the upper electrode plate includes a first hydrophobic layer and a first glass substrate.

[0010] Furthermore, the lower electrode plate includes a second glass substrate, a second hydrophobic layer, a photoconductive layer and a dielectric layer.

[0011] Furthermore, the second glass substrate, the photoconductive layer, the dielectric layer and the second hydrophobic layer are arranged in sequence from bottom to top, and the droplet is located on the second hydrophobic layer.

[0012] Furthermore, a first hydrophobic layer and a first glass substrate are sequentially arranged on the second hydrophobic layer.

[0013] Furthermore, a first electrode and a second electrode are etched on the photoconductive layer.

[0014] Further, the plug gauge includes a first plug gauge and a second plug gauge.

[0015] Furthermore, after projecting two parallel dark stripes, the potential gradient on the lower plate changes.

[0016] Furthermore, the droplets are droplets of deionized water.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention breaks through the uncontrollable limitation of the existing single-plane OEW device (only the lower plate) in terms of droplet splitting by constructing a double-plane OEW device between the upper and lower plates. The double-plane structure can increase the wetting area of ​​the droplet, increase the wetting force, and provide more stable and controllable droplet splitting conditions. At the same time, the present invention sets parallel dark stripes as optical virtual electrodes. These optical virtual electrodes are projected on the double-plane OEW device by a projector, and can achieve unlimited reconstruction, thereby achieving repeated splitting of droplets. The two parallel dark stripes remain non-overlapping, the stripes run through the droplets, and the direction of the stripes is perpendicular to the direction of the electric field on the lower plate. The use of optical virtual electrodes instead of physical electrodes breaks through the limitations of the number, size and position of droplet operations in the prior art. The design of parallel double dark stripes can provide two wetting forces of equal size and opposite direction. Under the joint action of the above two designs, uniform splitting of droplets can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic structural diagram of the device of the present invention;

[0020] Figure 2 It is the upper plate structure;

[0021] Figure 3 It is the lower plate structure;

[0022] In the figure, dark stripes 1, upper electrode plate 2, plug gauge 3, droplet 4, lower electrode plate 5, electrode 6, bias power supply 7, first hydrophobic layer 201, first glass substrate 202, first electrode 601, second electrode 602, second glass substrate 501, second hydrophobic layer 504, photoconductive layer 502, dielectric layer 503, first plug gauge 301, and second plug gauge 302. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0024] The present invention proposes a method for generating droplets on a dual-plane optically controlled electrowetting device. The structure of the device is shown in FIG. Figure 1 The upper plate structure is shown in Figure 2 The lower plate structure is as shown. Figure 3 The method comprises the following steps:

[0025] Obtain a dual-plane light-controlled electrowetting device, apply a bias voltage to the electrode 6 of the device, generate a transverse electric field, and then capture the contour and position of the droplet. Use a projector to project two parallel dark stripes 1 above the droplet according to the contour and position, and illuminate the rest of the droplet 4 to split the droplet. The dark stripes 1 do not overlap and penetrate the droplet 4. The direction of the dark stripes 1 is perpendicular to the electric field direction of the lower electrode 5 of the device. Assume that the direction of the transverse electric field is the X-axis, then;

[0026] The dual-plane light-controlled electrowetting device includes an upper plate 2 and a lower plate 5 . Electrodes 6 are provided at both ends of the lower plate 5 . The electrodes 6 include a first electrode 601 and a second electrode 602 . A plug gauge 3 is provided between the upper plate 2 and the lower plate 5 .

[0027] The device includes an upper plate 2 and a lower plate 5, and a feeler gauge 3 for determining thickness is placed between the upper and lower plates to ensure height.

[0028] A bias voltage is applied to electrodes 601 and 602 at both ends of the lower electrode plate 5 of the double-plane photo-controlled electrowetting chip.

[0029] Two parallel dark stripes 1 are projected on the dual-plane light-controlled electrowetting chip to change the potential gradient on the lower electrode plate 5 of the chip.

[0030] The direction of the two parallel stripes should be perpendicular to the direction of the electric field, that is, coincide with the Y-axis direction.

[0031] The width of the two parallel dark stripes should be between 1 / 2 and 1.5 times the radius of the droplet, and the widths should be the same. The width of the gap between the two dark stripes should be between 1 / 50 and 1 times the radius of the droplet. The midline of the gap between the two dark stripes should coincide with the midline of the droplet in the Y-axis direction.

[0032] Parallel dark stripes are generated by an artificial intelligence algorithm; the image of the droplets on the chip is captured in real time, including the outline of the droplets and the coordinates of the droplets on the chip, and is automatically generated based on the outline and position of the droplets.

[0033] The present invention designs a device with a dual-plane structure based on the principle of light-controlled electrowetting, and designs a method for droplet generation. The basic principle of the device is: the bias voltage applied to electrodes 601 and 602 generates a transverse electric field along the X-axis direction between electrodes 601 and 602. When light is irradiated to the photoconductive layer, the resistivity of the photoconductive layer decreases, and conversely, the resistivity of the unilluminated area increases. By projecting two parallel dark stripes to simulate the unilluminated area, two areas with larger resistivity are generated, and a larger voltage drop is generated on the dielectric layer 503 above the areas with larger resistivity. According to the Lippman-Young equation, the contact angles of these two areas become smaller, and two wetting forces of equal magnitude and opposite directions are generated. The upper electrode 2 increases the contact area between the droplet and the lower electrode, that is, increases the wetting force, so that the droplet splits more evenly.

[0034] The dual-plane light-controlled electrowetting device proposed in the present invention can increase the wetting area of ​​the droplet and increase the wetting force. The design of the parallel double dark stripes can provide two wetting forces of equal size and opposite direction. Under the combined effect of the above two designs, the droplet can be evenly split.

[0035] The process of device preparation and droplet generation of the present invention is as follows:

[0036] 1. Place the purchased quartz glass substrates 501 and 202 in an acetone solution for ultrasonic cleaning for 3 minutes, then place them in an isopropanol solution for ultrasonic cleaning for 5 minutes, and finally place them in deionized water for ultrasonic cleaning for 5 minutes. Then use a nitrogen gun to blow dry the substrate surface and dry it on a hot plate at 100°C for 5 minutes.

[0037] 2. A photoconductive layer of α-Si is deposited on the glass substrate obtained in 1 above by PECVD. The deposition temperature is 300°C, the chamber pressure is 50-100 Pa, the SiH4 flow rate is 20 sccm, the H2 flow rate is 40 sccm, and the deposition power is 50 W. Under the above process conditions, the deposition rate is 5-10 nm / min, and a 500-1000 nm α-Si photoconductive layer is obtained after 100 minutes.

[0038] 3. A layer of metal is deposited on the photoconductive layer 502 using PVD, and then etched to leave conductive electrodes 601 and 602.

[0039] 4. Spin coat the SU8 dielectric layer 503 with a spin coater at a speed of 3000 rpm for 1 minute. Dry on a hot plate at 100°C after spin coating, then heat to 150°C and dry for 30 minutes, and finally cool naturally.

[0040] 5. Spin Teflon hydrophobic layer 504 and 201 with a spin coater at a speed of 3000 rpm for 1 minute. After spin coating, dry on a hot plate at 100°C and finally cool naturally.

[0041] 6. Place plug gauges 301 and 302 with a thickness of 300 μm on the surface of the lower plate, then drop a drop of deionized water 4 on the chip, and finally cover the upper plate.

[0042] 7. Apply a bias voltage of 400V to electrodes 601 and 602, and then use an intelligent algorithm to capture the outline and position of the droplet. Use a projector to project two parallel dark stripes above the droplet, and illuminate the rest to split the droplet.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. Double-plane structure OEW device:

[0045] The present invention breaks through the uncontrollable limitation of droplet splitting in existing single-plane OEW devices (only the lower plate) by constructing a double-plane OEW device between the upper and lower plates. The double-plane structure provides more stable and controllable droplet splitting conditions.

[0046] 2. AI-generated optical virtual electrodes:

[0047] The present invention uses artificial intelligence (AI) to generate parallel dark stripes as optical virtual electrodes based on the position and volume of the droplet. These optical virtual electrodes are projected on a dual-plane OEW device through a projector, which can achieve unlimited reconstruction, thereby achieving repeated splitting of the droplet. The two parallel dark stripes remain non-overlapping, the stripes run through the droplet, and the direction of the stripes is perpendicular to the electric field direction on the lower electrode plate. Using optical virtual electrodes instead of physical electrodes breaks through the limitations of the number, size and position of droplet operations in the prior art.

[0048] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for generating droplets on a dual-plane optically controlled electrowetting device, characterized in that: The method comprises the following steps: A dual-plane light-controlled electrowetting device is obtained, and a bias voltage (7) is applied to an electrode (6) of the device to generate a transverse electric field. Then, after capturing the contour and position of a droplet, two parallel dark stripes (1) are projected above the droplet using a projector according to the contour and position, and the remaining part is illuminated to split the droplet (4). The dark stripes (1) do not overlap and penetrate the droplet (4). The direction of the dark stripes (1) is perpendicular to the electric field direction of the lower electrode plate (5) of the device. Assuming that the direction of the transverse electric field is the X-axis, then; The dual-plane light-controlled electrowetting device comprises an upper electrode plate (2) and a lower electrode plate (5), electrodes (6) are provided at two ends of the lower electrode plate (5), the electrodes (6) comprise a first electrode (601) and a second electrode (602), and a plug gauge (3) is provided between the upper electrode plate (2) and the lower electrode plate (5).

2. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 1, characterized in that: The method of projecting two parallel dark stripes (1) on the droplet using a projector according to the contour and position is as follows: the width of the dark stripes (1) is controlled to be between 1 / 2 and 1.5 times the radius of the droplet (4); the widths of the two dark stripes (1) are controlled to be the same; the width of the gap between the two dark stripes (1) is controlled to be between 1 / 50 and 1 times the radius of the droplet (4); the midline of the gap between the two dark stripes (1) coincides with the midline of the droplet in the Y-axis direction, and the Y-axis is perpendicular to the X-axis.

3. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 1, characterized in that: The upper electrode plate (2) comprises a first hydrophobic layer (201) and a first glass substrate (202).

4. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 3, characterized in that: The lower electrode plate (5) comprises a second glass substrate (501), a second hydrophobic layer (504), a photoconductive layer (502) and a dielectric layer (503).

5. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 4, characterized in that: The second glass substrate (501), the photoconductive layer (502), the dielectric layer (503) and the second hydrophobic layer (504) are arranged in sequence from bottom to top, and the droplet (4) is located on the second hydrophobic layer (504).

6. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 5, characterized in that: A first hydrophobic layer (201) and a first glass substrate (202) are sequentially arranged on the second hydrophobic layer (504).

7. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 4, characterized in that: A first electrode (601) and a second electrode (602) are etched on the photoconductive layer (502).

8. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 1, characterized in that: The plug gauge (3) comprises a first plug gauge (301) and a second plug gauge (302).

9. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 1, characterized in that: After projecting two parallel dark stripes (1), the potential gradient on the lower plate (5) changes.

10. The method for generating droplets on a dual-plane optically controlled electrowetting device according to claim 1, characterized in that: The droplets (4) are droplets of deionized water.

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