A liquid volume control device based on the principle of electrowetting and its fabrication method

Abstract

This invention discloses a liquid volume control device based on the principle of electrowetting and its fabrication method. The lower-level plate, from bottom to top, includes a first substrate, an electrode layer, a dielectric layer, and a hydrophobic layer. The upper-level plate includes a second substrate. A channel is formed on the bottom surface of the second substrate. One end of the channel communicates with an outlet hole, and the other end splits into two branches, which respectively connect to a first inlet hole and a second inlet hole. A loop-shaped channel is provided between the outlet hole and the connection point of the two branches. The liquid to be controlled is injected into the first inlet hole, and another immiscible liquid is injected into the second inlet hole. As the two liquids flow through the connection point of the two branches, the combined effect of the compression of the two liquids and the change in interfacial potential due to electrowetting separates the liquid to be controlled into droplets of different sizes related to the voltage. This invention has advantages such as novel design, simple structure, flexible operation, strong driving capability, high efficiency, high integration, and high degree of automation.

Description

Technical Field

[0001] This invention belongs to the field of digital microfluidics technology, and relates to microfluidics technology based on the principle of electrowetting, specifically to a liquid volume control device based on the principle of electrowetting and its preparation method. Background Technology

[0002] Lab-on-a-chip can be simply defined as a miniaturized and integrated microelectromechanical system capable of performing all processes of biochemical treatment and automatically completing the functions of traditional laboratories. Its goal is to integrate a complete analytical process on a single device, with advantages such as high integration, high precision, low consumption, and intelligence, and it has a very promising future in many fields such as biology and chemistry.

[0003] Microfluidics plays a crucial role as the driving force of lab-on-a-chip technology. Electrowetting technology manipulates droplets by altering their wetting properties on a medium surface using voltage, offering numerous advantages such as simple driving methods, flexible control, strong driving force, and high degree of automation. Summary of the Invention

[0004] The purpose of this invention is to provide a digital microfluidic chip that can accurately generate droplets of different sizes, thereby expanding the application scope of digital microfluidic technology based on improvements to existing droplet control devices.

[0005] The specific technical solution is as follows:

[0006] A liquid volume control device based on the principle of electrowetting includes a lower plate and an upper plate;

[0007] The lower-level board, from bottom to top, includes a first substrate, an electrode layer, a dielectric layer, and a hydrophobic layer.

[0008] The upper plate includes a second substrate; the bottom surface of the second substrate has a channel, and the top surface has an outlet hole, a first inlet hole and a second inlet hole. One end of the channel is connected to the outlet hole, and the other end is divided into two branches, which are respectively connected to the first inlet hole and the second inlet hole; a loop channel is provided in the channel between the outlet hole and the connection of the two branches.

[0009] The upper and lower plates are combined to form a liquid control device.

[0010] The liquid to be regulated is injected through the first inlet hole, and another immiscible liquid is injected through the second inlet hole. The two liquids are located between the hydrophobic layer and the second substrate channel. The electrode layer is the entire driving electrode. The two liquids flow into the channel and converge at the junction of the two branches. Due to the combined effect of liquid compression and electrowetting on the interfacial potential, the liquid to be regulated is separated into droplets of different sizes related to the voltage, which flow into the loop channel and then out through the outlet hole.

[0011] The principle of this invention is as follows: the electrode layer is the entire driving electrode; the liquid to be controlled is located in the channel between the hydrophobic layer of the lower plate and the second substrate. At the junction of the two branches flowing through the channel, due to the change in the interfacial wettability of the driving electrode after applying voltage, liquids of different sizes are drawn into the junction of the two branches. After being squeezed by another immiscible liquid at the junction of the two branches, they break into droplets of different sizes, flow into the loop channel, and then flow out from the outlet hole. The droplet size is related to the applied voltage, thus achieving precise control of the liquid volume by adjusting the voltage.

[0012] The number, shape, size, and "embedded" position of the driving electrodes are not strictly limited, and the design principle is to achieve their function.

[0013] The "droplet" to be controlled refers to a droplet that can be used for electrowetting drive on a dielectric layer. Its composition is not limited; it can be a single biological sample or a multi-component composition. At the same time, its size is not limited, but considering the limitations of the droplet drive structure, it is best to be between picoliters and several milliliters.

[0014] The electrode layer is a planar electrode.

[0015] Both the first substrate and the second substrate are made of insulating materials.

[0016] The dielectric layer is selected from non-conductive materials with a certain dielectric constant and breakdown resistance, preferably materials with high dielectric constant and strong breakdown resistance, including but not limited to SU-8.

[0017] The hydrophobic layer is made of materials that can reduce the surface tension of the droplets, including but not limited to Teflon.

[0018] The method for fabricating a liquid volume control device based on the principle of electrowetting includes the following steps:

[0019] Step 1, Fabrication of the lower electrode plate: Fabricate the electrode layer of the entire driving electrode on the first substrate; fabricate a dielectric layer on the electrode layer; fabricate a hydrophobic layer on the dielectric layer;

[0020] Step 2, Fabrication of the upper electrode: A channel is fabricated on the second substrate;

[0021] Step 3: Assemble the lower-level board and the upper-level board to form a liquid volume control device based on the principle of electrowetting.

[0022] Based on the principle of electrowetting, this invention proposes a novel microfluidic chip with liquid volume regulation function. By controlling the droplet transport and droplet splitting process in the digital microfluidic chip, the droplets are manipulated to generate droplets of different sizes that are related to voltage.

[0023] The liquid volume control digital microfluidic chip based on the principle of electrowetting provided by this invention has the following advantages:

[0024] (1) The digital microfluidic chip uses a single driving electrode and the channel is designed as a T-channel. The chip structure is simple and easy to operate.

[0025] (2) By combining laminar flow with electrowetting effect, the droplet transport and driving fracture process can be fully automated, with high speed, high throughput, high sensitivity and high precision, and can achieve precise control of droplet volume. Attached Figure Description

[0026] Figure 1 This is a cross-sectional structural diagram of the present invention.

[0027] Figure 2 This is a schematic diagram of the upper electrode plate channel structure of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0029] The liquid volume control device based on the electrowetting principle provided by this invention is realized through channel design and drive signal control, so it can be configured in various ways and can be configured in various digital microfluidic chips.

[0030] The schematic diagram of the principle structure of the present invention is shown in the longitudinal cross-sectional view. Figure 1 As shown. The driving electrode of the present invention is located on an insulating first substrate 100. The material used as the substrate is not fixed, as long as it is insulating; the number, size, and structure of the electrodes are not limited, and this specification only uses a single driving electrode as an example.

[0031] A liquid volume control device based on the principle of electrowetting includes a lower plate 201 and an upper plate 202;

[0032] The lower plate 201 includes, from bottom to top, a first substrate 100, an electrode layer 101, a dielectric layer 102, and a hydrophobic layer 103;

[0033] The upper-level plate 202 includes a second substrate 104; as Figure 1 and Figure 2 As shown, the bottom surface of the second substrate 104 has a channel, and the top surface has an outlet hole 301, a first inlet hole 302, and a second inlet hole 303. One end of the channel is connected to the outlet hole 301, and the other end is divided into two branches, which are respectively connected to the first inlet hole 302 and the second inlet hole 303. Between the outlet hole 301 and the connection of the two branches, the channel has a loop channel.

[0034] The upper plate 202 and the lower plate 201 are combined together to form a liquid control device.

[0035] The liquid to be regulated is injected through the first inlet hole 302, and another immiscible liquid is injected through the second inlet hole 303. The two liquids are located between the hydrophobic layer 103 and the channel of the second substrate 104. The electrode layer 101 is the entire driving electrode. The two liquids flow into the channel and converge at the junction of the two branches. Due to the combined effect of liquid compression and electrowetting on the interfacial potential, the liquid to be regulated is separated into droplets of different sizes related to the voltage, which flow into the loop channel and then out through the outlet hole 301.

[0036] Liquid is injected through the first inlet hole 302 and the second inlet hole 303. The droplet injector connected to the first inlet hole 302 is grounded, and the electrode layer 101 is positively charged. After the liquid is injected, it is located between the channel of the second substrate 104 and the hydrophobic layer 103. In this invention, the electrode layer 101 is selected as indium tin oxide (ITO), the dielectric layer 102 is selected as SU-8, the hydrophobic layer 103 is selected as Teflon, and the second substrate 104 is selected as PDMS.

[0037] A top view of the substrate channel structure of the present invention is shown below. Figure 2 As shown, the design incorporates a T-shaped structure at the connection point of the two branches. During the transport of the two liquids, they converge at the T-junction. Under the combined effects of compression and electrowetting altering the wettability at the interface, the liquid to be regulated splits into droplets of different sizes. It should be noted that the above is merely a principle description of the invention, and improvements and expansions to the device structure and applications are permitted without affecting its functionality.

[0038] In this invention, applying voltage to the driving electrode means that when the chip performs droplet manipulation, the voltage of the corresponding electrode is set to a non-zero value so that electrowetting can occur.

[0039] In this invention, "grounding" means that the voltage of the corresponding electrode is set to 0 or sufficiently close to 0 when the chip performs droplet manipulation.

[0040] Combination Figure 1 , Figure 2 The following is an implementable fabrication process for the liquid volume control digital microfluidic chip of the present invention:

[0041] Step 1, fabrication of the lower electrode plate 201: A metal thin film is formed on the first substrate 100 using processes such as spin coating, evaporation, and sputtering; the electrode layer 101 of the entire driving electrode is fabricated by photolithography; a dielectric layer 102 is fabricated on the electrode layer 101 by spin coating and photolithography; a hydrophobic layer 103 is fabricated on the dielectric layer 102 by spin coating and evaporation.

[0042] Step 2, fabrication of the upper electrode plate 202: The second substrate 104 and the channel are fabricated by spin coating and photolithography.

[0043] Step 3: Assemble the lower plate 201 and the upper plate 202 to form a liquid volume control device based on the principle of electrowetting.

[0044] Digital microfluidic manipulation methods can be used to automate various liquid operations.

[0045] The key structure of this invention lies in the combination of liquid transport within a T-channel and EWOD (electrowetting-on-dielectrics) droplet generation process, thereby achieving precise control of liquid volume.

[0046] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A liquid volume regulating device based on the principle of electrowetting, characterized in that, The lower plate (201) comprises a first substrate (100), an electrode layer (101), a dielectric layer (102) and a hydrophobic layer (103) from bottom to top. The lower plate (201) comprises a first substrate (100), an electrode layer (101), a dielectric layer (102) and a hydrophobic layer (103) from bottom to top. The upper plate (202) comprises a second substrate (104), the bottom surface of which is provided with a channel, and the top surface is provided with an outlet hole (301), a first inlet hole (302) and a second inlet hole (303), one end of the channel is communicated with the outlet hole (301), the other end is divided into two branches, and the two branches are communicated with the first inlet hole (302) and the second inlet hole (303) respectively; a return channel is arranged between the outlet hole (301) and the two branch connection positions. The upper plate (202) and the lower plate (201) are combined together to form a liquid control device. The to-be-controlled liquid is injected from the first inlet hole (302), and the other immiscible liquid is injected from the second inlet hole (303), and the two-phase liquid is between the hydrophobic layer (103) and the channel of the second substrate (104); the electrode layer (101) is the whole driving electrode. The two-phase liquid flows into the channel and converges at the connection position of the two branches, and under the joint action of liquid extrusion and electrowetting interfacial potential, the to-be-controlled liquid is separated into different size droplets related to voltage, flows into the return channel, and then flows out from the outlet hole (301).

2. A liquid volume regulating device based on the principle of electrowetting according to claim 1, characterized in that, The electrode layer (101) is a planar electrode.

3. The liquid volume regulating device based on the principle of electrowetting according to claim 1, characterized in that, The first substrate (100) and the second substrate (104) are both made of insulating materials.

4. The liquid volume regulating device based on the principle of electrowetting according to claim 1, characterized in that, The dielectric layer (102) is a high dielectric constant material SU-8.

5. The liquid volume regulating device based on the principle of electrowetting according to claim 1, characterized in that, The hydrophobic layer (103) is a hydrophobic material Teflon.

6. A method of manufacturing a liquid volume regulating device based on the principle of electrowetting according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: Step 1, preparing the lower plate (201): preparing the electrode layer (101) of the whole driving electrode on the first substrate (100); preparing the dielectric layer (102) on the electrode layer (101); preparing the hydrophobic layer (103) on the dielectric layer (102); Step 2, preparing the upper plate (202): preparing the channel on the second substrate (104); Step 3, assembling the lower plate (201) and the upper plate (202) to form a liquid volume control device based on the principle of electrowetting.

Images