An electrowetting droplet driving chip with a low number of electrodes and a droplet driving method

Abstract

The application discloses a low-electrode-number electrowetting droplet driving chip and a droplet driving method, wherein the electrowetting droplet driving chip comprises a substrate and electrodes arranged in sequence from bottom to top; the electrodes comprise a pair of right driving electrodes and left driving electrodes with gradually changing widths and arranged in a coplanar mode; an electrically non-conductive channel is arranged between the right driving electrodes and the left driving electrodes, the channel has a gradually changing width; the upper surfaces of the right driving electrodes, the left driving electrodes and the channel are uniformly paved with a dielectric layer; and the upper surface of the dielectric layer is paved with a hydrophobic layer. The application can realize the functions of droplet transportation, merging and splitting by using only two electrodes, and greatly reduces the complex control, circuit design and wiring required by the existing electrowetting droplet driving technology. The application can be widely applied to the technical fields of biomedical treatment based on digital microfluidic technology, enhanced heat transfer, fresh water collection, defogging and defrosting and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a droplet driving method, in particular to a low electrode number electrowetting droplet driving chip and a droplet driving method. BACKGROUND

[0002] Digital microfluidics is a kind of fluid control technology taking independent droplet as the control object, and droplet driving is the basis and foundation of digital microfluidics. In all droplet driving methods, electrowetting droplet driving has been widely used due to its low cost, fast response speed, and easy integration. Microfluidic technology based on electrowetting droplet control realizes the functions of droplet transportation, mixing, and splitting. At the same time, this droplet driving technology is also applied to optical devices, thermal and microelectronic applications.

[0003] In the current electrowetting droplet driving technology, the droplet driving is realized by using the difference in Laplace pressure on both sides of the droplet. This requires designing an electrode grid on the platform surface according to the size of the droplet to be driven, and sequentially connecting the voltage of the electrodes to realize the step-by-step transportation of the droplet.

[0004] There are mainly two structures, open and closed structures. Although both structures have their own advantages, they are limited by complex circuit design and complicated circuit control. For example, when it is necessary to combine with other liquid processing platforms and integrate other surface analysis devices, integration will be difficult and complex to implement.

[0005] Fudan University discloses an electrowetting microfluidic device and a control method (Chinese patent application number: CN200810038582.7). The disadvantages of this method are: a pair of electrodes can only complete one step driving, the driving distance and speed are limited, and the voltage polarity is required. Suzhou University discloses an electrowetting droplet driving method based on capacitance detection (Chinese patent application number: CN201410262084.6). The disadvantages of this method are: the relative position of the droplet and the driving electrode needs to be determined, multiple photoelectric couplers and capacitive couplers are required. Nanjing University of Technology discloses a medium droplet driving method based on negative dielectrophoresis driving mechanism (Chinese patent application number: CN201610183509.3). The disadvantages of this method are: the droplet needs to be placed in a surfactant solution environment, and a large number of electrodes are also required. South University of Science and Technology discloses a digital microfluidic droplet driving device (Chinese patent application number: CN201711171133.5). The disadvantages of this method are: multiple circuit control units are required, and the pulse alternating current needs to be greater than 500Hz. Zhangjiagang Industrial Technology Institute of Suzhou University discloses a droplet driving method of a composite digital microfluidic chip (Chinese patent application number: CN201810774278.2). The defects of this method are: the length of the plate area and the change rate of the droplet curvature radius need to be determined. Shenzhen Advanced Technology Research Institute discloses a digital microfluidic system and a droplet driving method (Chinese patent application number: CN201811095999.7). The defects of this method are: a large number of power supply driving modules and relay control modules are required. Suzhou University discloses a hybrid digital microfluidic chip and a droplet driving method (Chinese patent application number: CN202210273525.7). The defects of this method are: the interfacial force needs to be analyzed, and silicon oil needs to be arranged on the surface. SUMMARY

[0006] In view of the problems existing in the prior art, the present application discloses an electrowetting droplet driving chip with a low number of electrodes, which specifically comprises:

[0007] A substrate and electrodes are sequentially arranged from bottom to top, the electrodes include a pair of right driving electrodes and left driving electrodes with gradually changing widths and coplanar arrangement, an electrically non-conductive channel is arranged between the right driving electrodes and the left driving electrodes, a dielectric layer is uniformly laid on the upper surfaces of the right driving electrodes, the left driving electrodes and the channel, and a hydrophobic layer is laid on the upper surface of the dielectric layer.

[0008] The thickness of the substrate is 0.1-2mm, and the material of the substrate is calcified glass or flexible material of polyethylene terephthalate.

[0009] The right driving electrodes and the left driving electrodes are of asymmetric structure, wherein the width of the non-conductive area in the middle of the right driving electrodes and the left driving electrodes gradually changes.

[0010] The electrode is made by photolithography, laser etching, or chemical etching, and the material of the electrode is indium tin oxide, gold, silver, copper, metal alloy, or a combination of multiple materials.

[0011] The material of the dielectric layer is Perlyn C, silicon dioxide, tantalum pentoxide, polytetrafluoroethylene, polymethyl methacrylate, polydimethylsiloxane, or a combination of multiple materials.

[0012] The material of the hydrophobic layer is Teflon, polytetrafluoroethylene, porous medium oil immersion surface material, or micro-nano structure super-hydrophobic coating material.

[0013] The low-electrode-number electrowetting droplet driving method is based on the electrowetting droplet driving chip, and includes the following steps: placing a droplet in the middle position between the right driving electrode and the left driving electrode of the driving chip, using a low voltage to center the droplet, applying an alternating voltage to the electrode by a power supply, and moving the droplet from one side of the electrode to the other side; and increasing the amplitude of the voltage, and moving the droplet along the channel to a narrower side.

[0014] When two droplets are placed on both sides of the channel, the droplets are first centered by using a low voltage, then the amplitude is increased and an alternating voltage is applied, and when the droplets move close to each other, the voltage is disconnected, so that the droplets on both sides move close to the middle under the action of the electrowetting force, and finally the merging of the droplets is completed.

[0015] When a droplet is placed in the middle channel, the droplet is first centered by using a low voltage, then the amplitude is increased and an alternating voltage is applied, and the droplet is subjected to the action of the electrowetting force at both ends, the voltage is applied until the liquid bridge breaks, and the splitting of the droplet is completed.

[0016] By adopting the technical scheme, the low-electrode-number electrowetting droplet driving chip and the droplet driving method greatly reduce the number of electrodes required by the electrowetting droplet driving platform, greatly simplify the control circuit and the layout of the circuit, and make up for the shortcomings of the traditional technology; in addition, the method is more conducive to the integration of the microfluidic chip and other detection platforms and sensors, and is conducive to the use of space in complex droplet operations; at the same time, the method expands the selection of the base material, the dielectric layer material, and the hydrophobic layer material, reduces the dependence on processing equipment and environment, and is conducive to the popularization and application of the technology. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any inventive labor.

[0018] Figure 1 A schematic diagram of a low number of electrodes for droplet manipulation in electrowetting;

[0019] Figure 2 A flow chart of a low number of electrodes for droplet manipulation in electrowetting;

[0020] Figure 3 A schematic diagram of a device for a low number of electrodes for droplet manipulation in electrowetting chip;

[0021] Figure 4 A schematic diagram of a device module for a low number of electrodes for droplet manipulation in electrowetting chip;

[0022] Figure 5 A front view of a device for a low number of electrodes for droplet manipulation in electrowetting chip;

[0023] Figure 6 A left view of a device for a low number of electrodes for droplet manipulation in electrowetting chip;

[0024] Figure 7 A top view of a device for a low number of electrodes for droplet manipulation in electrowetting chip;

[0025] Figure 8 A schematic diagram of droplet merging on a low number of electrodes for droplet manipulation in electrowetting chip;

[0026] Figure 9 A schematic diagram of droplet splitting on a low number of electrodes for droplet manipulation in electrowetting chip.

[0027] In the figure: 1, substrate, 20, electrode, 2, right driving electrode, 3, left driving electrode, 4, dielectric layer, 5, hydrophobic layer, 6, droplet. DETAILED DESCRIPTION

[0028] In order to make the technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application:

[0029] In order to make the technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application:

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] like Figure 1 The illustrated low-electrode-number electrowetting droplet driving chip includes, from bottom to top, a substrate 1, electrodes 20, a dielectric layer 4, and a hydrophobic layer 5. The substrate 1 can be made of a hard material such as calcium glass, or a flexible material such as polyethylene terephthalate. The thickness of the substrate 1 is 0.1-2 mm.

[0032] The substrate 1 provides load-bearing support for each layer of the structure, ensuring its strength, stiffness, and structure while not interfering with the electrowetting effect. The materials used for substrate 1 can include, but are not limited to, polymer materials such as polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), and polydimethylsiloxane (PDMS); inorganic materials such as quartz, glass, silicon, and ceramics; metals and metal alloys; and combinations of multiple materials. The thickness of substrate 1 is selected based on the specific application scenario, ensuring that it does not interfere with the electrowetting effect.

[0033] Furthermore, the electrode 20 should be shaped as an asymmetrical structure, with the width of the non-conductive region between the two electrodes gradually decreasing. The electrode 20 includes a right driving electrode 2 and a left driving electrode 3, both with gradually varying widths and coplanar arrangement, with a non-conductive channel between them. The right driving electrode 2 and the left driving electrode 3 are in the same plane, have equal thickness, and gradually increase in width. A dielectric layer 4 is deposited on the surface of the right driving electrode 2 and the left driving electrode 3, and a hydrophobic layer 5 is deposited on the surface of the dielectric layer 4. The droplet 6 is placed on the surface of the hydrophobic layer 5 and remains in contact with it at all times.

[0034] The right driving electrode 2 and the left driving electrode 3 should be made of good conductive materials, including but not limited to indium tin oxide (ITO), gold, silver, copper, and metal alloys, as well as combinations of multiple materials.

[0035] Furthermore, the asymmetric electrode 20 can be processed using methods such as photolithography, laser etching, and chemical etching.

[0036] Further, the electrode 20 can also be processed into multiple pairs, which can avoid the limitation of volume matching of the driving liquid.

[0037] Further, the dielectric layer 4 provides protection between the working droplet and the electrode, ensuring that the device will not cause damage to the chip due to leakage. The material of the dielectric layer 4 can include but is not limited to Parylene C, silicon dioxide, tantalum pentoxide, polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polydimethylsiloxane (PDMS), etc., and combinations of various materials.

[0038] Further, the hydrophobic layer material 5 should ensure low adhesion on the surface, and the selected material can include but is not limited to Teflon, polytetrafluoroethylene (PTFE), etc. common hydrophobic materials, or porous medium oil immersion surface, or micro-nano structure super-hydrophobic coating.

[0039] A low-electrode-number electrowetting droplet driving method uses the above low-electrode-number electrowetting droplet manipulation chip, places the droplet on a pair of electrodes 20 on the chip, and uses low voltage to center the droplet. Then, an alternating voltage is applied to the electrodes 20 by the power supply, and the droplet will move from one side of the electrode to the other side. In this method, through the design of the asymmetric electrode, when the voltage is applied on the electrode pair, the droplet on the surface will be subjected to asymmetric electrowetting force. For a common hydrophobic surface placed in an oil environment, a super-hydrophobic surface in an air environment, or an oil-wetted surface (oil environment or air environment), the adhesion of the droplet on it is very small, so it can meet the driving of the droplet under the asymmetric electrowetting force.

[0040] As shown in Figure 1 The principle diagram of the low-electrode-number electrowetting droplet manipulation disclosed by the application is shown. The droplet 6 is placed in the gap position between the right driving electrode 2 and the left driving electrode 3. A dielectric layer 4 is laid on the surface of the electrode, and a hydrophobic layer 5 is laid on the surface of the dielectric layer. An alternating voltage is applied between the electrode 2 and the electrode 3, the contact angle of the droplet 6 is reduced, the droplet is spread, and the contact line is subjected to the action of the electrowetting force. Since the electrowetting forces on both sides of the droplet are not equal, the droplet will be driven in a certain direction.

[0041] Further, by changing the shape structure of the gap between the two electrodes 20, only two electrodes are needed to realize the functions of long-distance transport, merging, splitting, etc. of the droplet.

[0042] Further, the droplet is a single-component or multi-component polar liquid, or a single-component or multi-component conductive liquid.

[0043] Embodiment: as shown in Figure 7As shown, the right driving electrode 2 and the left driving electrode 3 are arranged on the substrate 1, forming a non-conductive channel between the two electrodes. A dielectric layer 4 covers the entire surface, and a hydrophobic layer 5 is deposited on the surface of the dielectric layer 4. The width of the channel between the two electrodes gradually narrows, allowing a droplet 6 to be placed on this platform. Figure 2 The illustrated operating steps enable the directional transport of droplets. First, the droplet is placed at one end. A low voltage is applied to position the droplet between the two electrodes. Then, the voltage amplitude is increased, and the droplet begins to move along the narrower side of the channel. Once it reaches the desired position, the sensor sends information to the power supply, which is then turned off, completing the droplet's movement.

[0044] like Figure 8 As shown, the right merging electrode 2 and the left driving electrode 3 are deposited on the substrate 1. A channel that narrows and then widens is formed between the two electrodes, and the dielectric layer 4 is spread on it. Droplets 6 are placed on both sides of the channel, and then... Figure 2 The process involves moving the droplets on both sides towards the center under the influence of electrowetting force, eventually merging the droplets.

[0045] The droplets 6 include, but are not limited to, polar liquids such as water, ethanol, and inorganic aqueous solutions, as well as other non-polar liquids.

[0046] By utilizing different electrode designs, the electrowetting droplet driving method of this invention, with its low electrode count, can achieve droplet splitting. Specifically:

[0047] like Figure 9 As shown, the left driving electrode 3 and the right driving electrode 2 are deposited on the substrate 1. A channel that narrows and then widens is formed between the two electrodes, and the dielectric layer 4 is spread on it. A droplet 6 is placed in the middle channel, and then... Figure 2 By following these steps, the droplet splitting process can be completed. After the splitting is complete, disconnect the power switch.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An electrowetting droplet driving chip with a low number of electrodes, characterized in that The application relates to an electrowetting liquid drop driving chip, which comprises a substrate (1) and an electrode (20) arranged in sequence from bottom to top, the electrode (20) comprises a pair of right driving electrodes (2) and left driving electrodes (3) with gradually changed widths and arranged in a plane, a non-conductive channel is arranged between the right driving electrodes (2) and the left driving electrodes (3), the upper surfaces of the right driving electrodes (2), the left driving electrodes (3) and the channel are uniformly paved with a dielectric layer (4), and the upper surface of the dielectric layer (4) is paved with a hydrophobic layer (5). The right driving electrodes (2) and the left driving electrodes (3) are asymmetric structures, wherein the widths of the middle non-conductive regions of the right driving electrodes (2) and the left driving electrodes (3) gradually change. A liquid drop driving method based on the electrowetting liquid drop driving chip comprises the following steps: A drop is arranged at a middle position between the right driving electrodes (2) and the left driving electrodes (3) of the driving chip, the drop is centered by using low voltage, an alternating voltage is applied to the electrode (20) by a power supply, the drop moves from one side of the electrode to the other side, the amplitude of the voltage is increased, and the drop starts to move along the channel to a narrower side. The thickness of the substrate (1) is 0.1-2 mm, and the material of the substrate (1) is a flexible material such as calcified glass or polyethylene terephthalate.

2. The low number of electrodes electrowetting droplet driving chip according to claim 1, characterized in that The electrode (20) is manufactured by using a photoetching, laser etching or chemical etching method, and the material of the electrode (20) is indium tin oxide, gold, silver, copper, a metal alloy or a combination of multiple materials.

3. The low number of electrodes electrowetting droplet driving chip according to claim 1, characterized in that: The material of the dielectric layer (4) is paralyne C, silicon dioxide, tantalum pentoxide, polytetrafluoroethylene, polymethyl methacrylate, polydimethylsiloxane or a combination of multiple materials.

4. The low number of electrodes electrowetting droplet driving chip according to claim 1, wherein: The material of the hydrophobic layer (5) is polytetrafluoroethylene, porous medium oil immersion surface material or micro-nano structure super-hydrophobic coating material.

5. The low number of electrodes electrowetting droplet driving chip according to claim 1, characterized in that: When two drops are arranged at two sides of the channel, the drops are centered by using low voltage, the amplitude is increased, an alternating voltage is applied, the drops move to approach each other, the voltage is disconnected, therefore the drops at the two sides approach each other under the action of the electrowetting force, and finally the merging of the drops is completed.

6. The low number of electrodes electrowetting droplet driving chip according to claim 1, wherein: When a drop is arranged at a middle channel, the drop is centered by using low voltage, the amplitude is increased, an alternating voltage is applied, the drop is subjected to the electrowetting force of two ends, the voltage is applied until the liquid bridge is broken, and the splitting of the drop is completed.

7. The low number of electrodes electrowetting droplet driving chip according to claim 1, characterized in that: ​

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