An electro-microfluidic driven panel and its method for controlling particle assembly within a droplet array

Abstract

This invention discloses an electro-microfluidic driven panel and a method for controlling particle assembly within a droplet array. Utilizing a dual-electrode strategy, this invention allows for more direct electrode pattern design based on the target pattern, generating a particle assembly structure that visually approximates the electrode pattern. It maintains the advantage of coplanar electrodes significantly altering the assembly structure and the ability to control the spatial distribution of particles. Furthermore, by employing strategies such as extending the electrode pattern or adjusting the electrode spacing, pattern defects caused by low electric field strength at the droplet edges are reduced. By simply adjusting the confinement effect of the electrodes and microgrid within the panel, uniform droplets can be generated, and the relative consistency of the array droplet shape can be controlled, further improving the accuracy of the assembly structure.

Description

Technical Field

[0001] This invention belongs to the field of microfluidics technology, specifically relating to an electro-microfluidic driving panel and a method for assembling controlled particles inside a droplet based on the electro-microfluidic driving panel. Background Technology

[0002] Dielectrophoresis occurs under the condition of a non-uniform electric field. When both the object and the surrounding medium can be polarized by the electric field, the dielectrophoretic force will be generated and act on the interface between the particle and the surrounding medium, causing the object to move along the electric field gradient direction to the region of high or low electric field strength.

[0003] Traditional dielectrophoresis-based particle assembly techniques are typically applied to large-volume liquid environments. However, the randomness of particle density distribution in such environments, with significant variations between different regions, significantly impacts the accuracy of the assembled structure. Furthermore, once the particle assembly structure is formed under an electric field, the transition from assembly to a uniform distribution is slow and dependent on Brownian motion, thus placing demands on liquid viscosity, temperature, and particle size. Introducing droplets with relatively uniform particle density and arraying these uniformly sized droplets over a large area can effectively address these issues. However, when manipulating and assembling particles within droplets using an electric field, the droplet shape and size significantly affect the internal electric field distribution. Therefore, higher demands are placed on the manipulation and assembly of particles within arrayable and precisely controllable droplets: the droplet size must be relatively uniform, the droplet array shape must be relatively consistent, and the electric field distribution near the curved interface of the droplet differs significantly from that at the wetting interface, requiring corresponding matching electrode designs.

[0004] Currently, the manipulation or assembly of micron-sized particles based on dielectrophoresis, due to the lack of confinement by the liquid, results in particles, regardless of whether they are subjected to positive or negative dielectrophoretic forces, typically assembling at the edges, center, or gaps of the electrodes, forming only 2D assembly patterns or short-range 3D pattern structures. For particles inside larger droplets, the electrode designs currently used are typically open or closed digital rectangular electrode arrays (refer to digital microfluidic chips). Existing open-design digital microfluidic chips aim to apply an electric field to the gaps between planar electrodes, making it difficult to construct a sufficient and precisely controllable electric field gradient within the unit electrode (usually a square electrode or a quasi-square electrode with serrated edges), thus hindering effective control over droplet particle assembly. Closed digital microfluidics employ a sandwich device structure, generating an electric field distribution approximately perpendicular to the electrode plane through upper and lower planar electrodes for droplet movement manipulation. However, this design has a relatively unidirectional electric field, resulting in particle assembly typically only being able to align along the electric field lines, limiting the morphology and orientation of the assembled particles. CN114307785A discloses a method and emulsion system for precisely controlling the electro-response behavior of particles in emulsion droplets. While this patent can form diverse and actively controllable assembly structures within single or multiple droplets, and precisely adjust the position of the particle assembly structures within the droplets, the assembly structures in this patent are formed by simple electrode patterns. There is no intuitive or significant connection between the electrode patterns and the assembly structures. Therefore, when designing the assembly structures, the actual design requires multiple simulations and iterations of the electric field distribution corresponding to the electrode patterns. This indirect information, the electric field distribution map, is used to correlate with the assembly structure, which presents design difficulties for customizing the particle assembly structures. Thus, existing electrode designs cannot achieve a controllable gradient field distribution within the droplets, and the electric field direction is diverse and controllable, making it difficult to effectively control the droplets and the particles within them. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes an electro-microfluidic driving panel for controlling particle assembly within a droplet array. Utilizing a dual-line electrode strategy, electrode patterns can be designed more directly for the target pattern, generating a particle assembly structure that visually approximates the electrode pattern. This maintains the advantage of coplanar electrodes significantly altering the assembly structure and the ability to control the spatial distribution of particles. Furthermore, by employing strategies such as extending the electrode pattern or adjusting the electrode spacing, pattern defects caused by low electric field strength at the droplet edges are reduced. Additionally, by simply adjusting the confinement effect of the electrodes and microgrid within the panel, uniform droplets can be generated, and the relative consistency of the array droplet shape can be controlled, further improving the accuracy of the assembly structure.

[0006] In view of this, a first aspect of the present invention is to provide an electro-microfluidic driven panel, the electro-microfluidic driven panel comprising an electrode layer and an emulsion layer;

[0007] The electrode layer is a planar electrode with a patterned electrode array. Among them, the patterned electrode unit consists of at least a pair of discrete double-line electrodes forming an electrode pattern; the pair of discrete double-line electrodes are respectively connected to the signal terminal and the ground terminal, and the discrete double-line electrodes can form a non-uniform electric field.

[0008] The emulsion layer is in contact with the electrode layer. The emulsion layer includes an outer-phase liquid, inner-phase droplets surrounded by the outer-phase liquid, and particles with a solid content of more than 0.5 wt% dispersed inside the droplets. The inner-phase droplets are affected by positive dielectrophoretic force, and the particles are particles affected by positive or negative dielectrophoretic force, preferably particles affected by negative dielectrophoretic force.

[0009] One or more of the above electrode units are separated by unit walls higher than the electrode plane, enclosing a unit cell grid containing one or more of the electrode units, for spacing the inner-phase droplets and for determining the size and shape of the inner-phase droplets after the planar electrode is powered.

[0010] According to the electro-microfluidic driving panel of the present invention, the double-line electrode uses two parallel or nearly parallel thin wires as a pair of discrete electrodes, which can minimize the electrode surface area. The discrete electrodes are equivalent to two thin lines, and a high electric field strength in a narrow area range is generated by the electrode gap between the two thin lines, so that the electric field gradient distribution inside the inner-phase droplets can be precisely controlled. However, since the droplet deformation also affects the electric field distribution, it is necessary to consider the influence of the planar electrode design and droplet deformation at the same time. For example, at the edge of the wetting substrate of the inner-phase droplet, the interface between the inner-phase droplet and the outer-phase liquid usually presents a curved surface, resulting in different electric field distributions in the central region and the interface region inside the droplet (usually the electric field strength in the interface region decreases). To solve this problem, an adaptive electrode pattern needs to be designed to solve the problem of poor similarity matching of the assembled pattern caused by droplet size differences or wettability differences. The top view of the inner-phase droplet is divided into a wetting area and a non-wetting area. The electrode line width in the wetting area is w1, and the parallel gap between the double lines is g. Particle assembly can still occur on the curved surface of the inner-phase droplet (the interface between the inner and outer phases of the droplet is a curved surface). It is necessary to design the electrode specifically, that is, the electrodes covered in the non-wetting area are adjusted to: the gap between the double-line electrodes < g or the line width of the double-line electrodes > w1, or the gap between the double-line electrodes < g and the line width of the double-line electrodes > w1; or extend the electrode pattern, that is, the length of the electrode in the cell grid > the length of the target assembled pattern.

[0011] According to the electro-microfluidic drive panel of the present invention, in the electrode unit, the sum of the widths w2 of the discrete bilinear electrodes and the gaps between them ranges from 0.1 to 3000 μm, preferably 1 to 500 μm. The electrode length varies depending on the assembly structure design and there is no uniform parameter. w1 must satisfy: 0.05 μm < w1 < w2 / 3, and g must satisfy: 0.05 μm < g < w2 / 3. When the gap is too large, the high-intensity electric field diffuses into higher spaces, making it difficult for the particle assembly structure to correspond to the bilinear electrode pattern. In a specific embodiment, w2 ranges from 1 to 150 μm, preferably about 40 to 60 μm; w1 is 8 to 20 μm, for example 15 μm; and g is 1 to 50 μm, more preferably 10 to 30 μm. The dual-line electrode can be customized with any pattern as needed, including numbers, text, letters, geometric shapes, etc., and is not limited by large-area patterns on the electrode surface (such as the electric field strength at the edge of the electrode with a large-area pattern being higher than that in the center of the electrode). This is beneficial for generating a local electric field distribution that matches the electrode pattern on the electrode surface, thereby controlling the patterned distribution of particles in the emulsion layer and avoiding the problem of excessive difference between the field strength inside the droplet and the pattern on the electrode surface.

[0012] According to the electro-microfluidic driven panel of the present invention, the bottom surface of the unit grid in contact with the electrode layer can be square, with the side length of the square ranging from 200-3000 μm, for example 350 μm; the width is the side length of the bottom square, and the height is the unit grid height, with a height-to-width ratio of 1:1 to 5, preferably 1:1 to 3.5, for example 1:2.3. The height-to-width ratio of the droplets has a significant impact on the wetting area of ​​the inner phase droplets on the electrode plate surface, thus significantly affecting the electric field distribution and thereby changing the assembly structure. The smaller height-to-width ratio of the present invention can compress the shape of the inner phase droplets, resulting in the wetting area of ​​the inner phase droplets covering a larger area of ​​the electrode pattern, thereby avoiding distortion and weakening caused when the electric field enters the outer phase liquid. Preferably, the unit walls can be constructed using polymer mesh material (PET screen), photoresist (SU-8 series negative adhesive), or other materials capable of forming micron-sized cells.

[0013] Preferably, the unit grid is covered with an upper cover plate to seal the droplets and prevent the droplets from evaporating and affecting the droplet size and particle volume ratio. If the droplets become smaller, the particle volume ratio will increase. If the ratio increases to an extreme value (dense accumulation), controllable electric field assembly will not be possible.

[0014] According to the electro-microfluidic driven panel of the present invention, in the emulsion layer, a single droplet can correspond to at least one electrode unit. Before the electrode layer is energized, a single inner-phase droplet of a target size or multiple inner-phase droplets of a target size after electrofusion can be distributed within a cell grid enclosed by the cell walls to avoid the droplet electrofusion effect that is easily generated when voltage is applied to the electrode layer. For example, when multiple inner-phase droplets smaller than the side length of the cell grid are distributed within a cell grid, electrofusion can occur after energization, thereby increasing the droplet size. The size of the fused inner-phase droplet is affected by the volume ratio of the initial inner-phase droplet in the cell grid; preferably, the limiting volume of the fused inner-phase droplets is close to but smaller than the volume occupied by the cell grid, that is, when viewed from a plane perpendicular to the electrode array, the equator of the inner-phase droplet is tangent to the side length of the cell wall. In a specific embodiment, under the condition of a preferred cell grid size, the diameter of the controlled inner-phase droplet after electrofusion is about 200-500 μm, preferably 350 μm.

[0015] According to the electro-microfluidic drive panel of the present invention, the electrode units are configured with the same or different electrode patterns, thereby enabling different electrode units to drive the particles in the droplet to assemble into the same or different structures.

[0016] According to the electro-microfluidic drive panel of the present invention, adjacent electrode units to which the same signal is applied can be interconnected or exist independently. Interconnected adjacent electrode units can greatly reduce design complexity and are beneficial for achieving unified control of arrayed droplets; in an array of independently existing electrode units, each unit can be individually powered and controlled. In this case, the electrode wiring is relatively complicated, but the advantage is that each electrode unit pair can be controlled individually, so that the particle movement and assembly structure of the internal phase droplets at different positions in the same emulsion system are different from each other.

[0017] In the electro-microfluidic drive panel according to the present invention, the electrode units can be considered as designed on the same plane. For electrode structure designs on flexible planar substrates, the case where the substrate is not coplanar due to bending is also considered as planar electrodes.

[0018] According to the electro-microfluidic driving panel of the present invention, the electrode layer is composed of a conductive plating layer on a solid substrate, including indium tin oxide (ITO) glass, gold-plated glass, and copper-plated printed circuit board (PCB); electrode patterns are formed by photolithography, soft photolithography, laser engraving, 3D printing, screen printing, or other methods on the conductive plating layer. Preferably, the electrode layer is obtained by photolithography and etching of indium tin oxide (ITO) glass to obtain a patterned electrode array.

[0019] According to the electro-microfluidic drive panel of the present invention, the surface of the electrode layer can be modified to give it the properties of being affinity-for-emulsion outer phase and repellent-for-emulsion inner phase. The modification treatment includes: surface treatment with dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, or modification of the electrode surface by means of plasma cleaning machine, spin coating of thin film material, or vapor deposition.

[0020] According to the electro-microfluidic driven panel of the present invention, the emulsion layer corresponds to an emulsion system that is not limited to a specific category, and can be selected from a water-in-oil system, an oil-in-water system, an aqueous two-phase system, or an oil two-phase system.

[0021] According to the electro-microfluidic driven panel of the present invention, in the emulsion layer, the diameter of the inner phase droplets is in the range of 1-3000 μm, preferably 1-500 μm; in a specific embodiment, the diameter of the inner phase droplets is 1-100 μm; the diameter of the particles inside the droplets is smaller than that of the inner phase droplets, and the particle size is in the range of 0.1-100 μm, preferably 0.1-10 μm; in a specific embodiment, the particle size is 4 μm.

[0022] According to the electro-microfluidic driven panel of the present invention, the emulsion can be formed by chip microfluidics, capillary microfluidics, mechanical emulsification, ultrasonication, thin film emulsification, or colloid milling. The inward droplets can enter the cell grid according to gravity or the difference in wettability between the inner and outer phases and the surface. For example, the particle-dispersed emulsion inner phase can be generated into uniformly sized droplets using microchannel structures such as T-channel method, co-current focusing method, or flow focusing method. The particle-loaded emulsion is then transferred to the electrode layer pattern array, and the droplets are filled into the cell grid by gravity sedimentation, fluid flow filling, scraping, self-assembly, etc.; or the droplets can be filled into the cell grid by inkjet printing.

[0023] According to the electro-microfluidic driven panel of the present invention, in the emulsion layer, the inner phase droplets preferably use a medium with a high dielectric constant and a lower conductivity relative to the outer phase, thereby making it easier for the droplets to be located at the electrode gaps, increasing the electric field strength inside the droplets, and making it easier for the electro-controlled assembly of the particles to occur.

[0024] According to the electro-microfluidic driven panel of the present invention, the particles exhibit affinity for the inner phase and reluctance towards the outer phase of the emulsion, such that most droplet particles (>50%, preferably >95%) are dispersed in the internal space of the inner phase droplet.

[0025] According to the electro-microfluidic driven panel of the present invention, the electrical conductivity or dielectric constant of the particles is less than that of the internal liquid phase, allowing the particles to move towards lower electric field strength under the influence of an electric field. When subjected to a positive dielectric force, they can also move towards higher electric field strength.

[0026] According to the electro-microfluidic driven panel of the present invention, the preferred particle density is relatively high compared with the internal phase density of the emulsion. After the particles are left to stand in an environment without an electric field, they settle to the bottom of the droplet. Under an applied electric field, the particles can form chains under the interaction of dipole moments and are subjected to negative permittivity to form a specific assembly structure.

[0027] According to the electro-microfluidic drive panel of the present invention, when using preferred particles and droplets, as the electric field strength increases, the position of the assembly structure gradually moves from the bottom of the droplet to the top of the droplet.

[0028] According to the electro-microfluidic driven panel of the present invention, the external phase of the emulsion layer can be an oil phase other than a curable liquid, such as silicone oil, hexadecane, olive oil, mineral oil, etc., which are incompatible or poorly miscible with the internal phase droplets under normal conditions (room temperature and standard atmospheric pressure, without the addition of crosslinking agents). Preferably, the external phase exhibits properties of low volatility and relative stability under electro-controlled conditions, and is less prone to generating strong flow fields with velocities greater than 10 μm / s.

[0029] According to the electro-microfluidic driven panel of the present invention, the emulsion internal phase includes, but is not limited to, using an aqueous medium, such as: deionized water (hereinafter referred to as water), a mixture of water and the following internal phase additives: polyethylene glycol diacrylate (PEG-DA), dyes, surfactants, sugars (sucrose, glucose, etc.), and trace amounts of salts (such as NaCl, KCl, etc., with a concentration of 10 in water). -1 (below mol / L); biological liquids, such as low-salt buffers, plasma, protein solutions, etc.; high dielectric constant polar solvents that are immiscible with the external phase, including acetamide, diphenylamine, docosane, etc.

[0030] According to the electro-microfluidic driven panel of the present invention, the ratio range of the external phase to the internal phase of the emulsion needs to meet the basic conditions for emulsion formation, and the preferred ratio of the internal phase to the external phase volume is in the range of 5-40%; the ratio of the total mass of particles to the mass of the internal phase is in the range of 0.1-30%.

[0031] In a specific embodiment, the emulsion layer has an external liquid phase that is a mixture of silicone oil and a surfactant, wherein the surfactant is selected from one or more of KF-6017, MC-215, ES-5300, ES-5612, etc.; the internal phase of the emulsion is water, and the particles dispersed inside the droplets are selected from one or more of polystyrene particles, silica particles, yeast cells, chlorite particles, etc., preferably polystyrene particles.

[0032] A second aspect of the present invention provides a method for assembling a controllable particle structure inside a droplet based on the above-described electro-microfluidic driven panel:

[0033] S1: Apply alternating current AC1 to the patterned electrode array to control the fusion of internal phase droplets in the unit grid to form a uniform droplet array;

[0034] S2: Apply AC2 to the patterned electrode array; at this time, a non-uniform electric field is formed between the discrete bipolar electrodes; under the action of positive permittivity, the inner phase droplets of the emulsion automatically align with the high field strength region within the unit grid. With the assistance of the confinement effect of the space enclosed by the unit grid, the field strength inside the inner phase droplets is significantly enhanced, resulting in a local electric field distribution that matches the electrode pattern; the particles in the inner phase droplets form chains under the interaction of dipole moments and are subjected to positive or negative permittivity, approaching or moving away from the electrode pattern, thereby controlling the assembly structure and position of the internal particles.

[0035] Furthermore, the shape and position of the particle assembly structure can be changed by adjusting the electric field strength and frequency.

[0036] According to the method of the present invention, in step S2, when an alternating current is applied, when the particles are subjected to a positive permittivity, the particles move towards the high field strength distribution region and assemble, forming a "light-shielding" particle assembly pattern in the region corresponding to the electrode; when the particles are subjected to a negative permittivity, the particles move towards the low field strength distribution region and assemble, forming a "light-transmitting" particle assembly pattern in the region corresponding to the electrode. Preferably, the particles are particles subjected to a negative permittivity.

[0037] According to the method of the present invention, in step S2, when using the preferred particles subjected to negative dielectric force, as the electric field strength increases, the position of the assembled structure gradually moves from the bottom of the droplet to the top of the droplet, and the assembled pattern has an enlarged size effect when viewed from a top view.

[0038] According to the method of the present invention, in step S1, the frequency range of the applied alternating current AC1 is 1-1000kHz, and the amplitude range is 20-600Vpp; preferably, the frequency of AC1 is 200kHz, and the amplitude range is 80Vpp-200Vpp.

[0039] According to the method of the present invention, in step S2, the frequency range of the applied alternating current AC2 is f > 20kHz, and the amplitude range is 1-200Vpp; preferably, the frequency of AC2 is 400kHz, and the amplitude is 12Vpp.

[0040] Beneficial effects

[0041] 1. Compared to techniques such as interdigitated electrodes and wall electrodes for the array enrichment or assembly of dispersed particles in large-volume liquids, emulsion droplets ensure uniform particle concentration, contributing to improved uniformity of large-area particle assembly structures. They also avoid interference between particles in adjacent droplet areas, offering potential for information encoding and biosensor applications. Compared to traditional interdigitated electrodes and wall electrodes, the electrode structure of this invention's electro-microfluidic driven panel features a customized double-line pattern. This strategy reduces the area occupied by the electrode surface, effectively mitigating the outward diffusion of strong electric field regions inherent in planar electrode designs. The electric field is primarily confined to the electrode gaps, and precise control of the electric field through the electrode gap pattern drives the assembly of particles within the emulsion's inner phase droplets, forming an assembly structure with a specific pattern. This demonstrates a significant advantage in the precise control of the patterned assembly of emulsion inner phase droplets and internal particles.

[0042] 2. To address the issue of different electric field distributions between the central region and the interface region inside the droplet, this invention employs a strategy of extending the electrode pattern or adjusting the electrode spacing to reduce pattern defects caused by low electric field strength at the droplet edge. This provides a certain degree of adaptability for forming the target particle assembly pattern inside the droplet. That is, regardless of whether the droplet projection area forms an inscribed circle with the pixel unit, the assembly pattern is still similar to the electrode design, achieving the effect of matching the particle assembly with the ideal pattern.

[0043] 3. The electro-microfluidic drive panel of the present invention has the advantages of simple power application and array-driven assembly of intraphase droplets in emulsion systems. Furthermore, the panel controls the size and shape of droplets uniformly through unit walls, improving the consistency of the electric field distribution of the droplet array. It can precisely manipulate the particles inside the droplets and form micron-level patterns within the droplets.

[0044] 4. The arrayed droplet particle assembly pattern has the ability to output information. For example, by using laser irradiation to project micron-level information onto the pattern, it can be directly read by the human eye, potentially for anti-counterfeiting applications. Furthermore, solidifying the droplets to form particles allows for the storage of micron-level pattern information within the particles, enabling the drive panel to construct arrayed coded particles. Attached Figure Description

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the electro-microfluidic drive panel structure of the present invention.

[0047] Figure 2 This is a schematic diagram of the dual-line electrode design of the electro-microfluidic drive panel of the present invention. From left to right, it shows the ordinary dual-line electrode design, the electrode extension strategy and the electrode spacing adjustment strategy of the present invention.

[0048] Figure 3 The image shows the array pattern of the planar electrodes in Example 1 (right) and the optical microscope pattern of the particle assembly structure after an electric field is applied (left).

[0049] Figure 4 The image shows the array pattern of the planar electrodes in Example 2 (right) and the optical microscope pattern of the particle assembly structure after an electric field is applied (left).

[0050] Figure 5 The image shows the array pattern of the planar electrodes in Example 3 (right) and the optical microscope pattern of the particle assembly structure after an electric field is applied (left). Detailed Implementation

[0051] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather should be interpreted based on the principle of allowing the inventors to appropriately define the terminology for the best interpretation, and based on its meaning and concept corresponding to the technical level of the invention. Therefore, the description herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention; thus, it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the invention.

[0052] The electro-microfluidic driven panel proposed in this invention ensures that emulsion droplets are filled into a micro-unit array. Upon application of electricity, electro-aggregation is achieved, forming uniform droplets. Simultaneously, the particle assembly within the droplet array is regulated under the influence of an electric field. Based on pre-designed electrode structure geometry and dimensions, droplet arrays with different particle assembly patterns are formed under the influence of the electric field. The displayed information within the droplet array can be read using magnifying glasses, macro cameras, laser imaging, etc., thus possessing potential anti-counterfeiting applications. Furthermore, the technical method for precisely controlling particle assembly within the droplet array provides a new approach for the application of emulsion droplets in biological, chemical, and medical fields.

[0053] Figure 1 , Figure 2 This is for illustrative purposes only and does not impose any restrictions on the geometry of the electrode array.

[0054] in, Figure 1 This is a schematic diagram of the electro-microfluidic drive panel structure of the present invention.

[0055] Figure 2It is a schematic diagram of the design of a double-line electrode for the problem of different electric field distributions in the central region and the interfacial region inside the droplet. Among them, the top view of the internal-phase droplet is divided into a wetting region and a non-wetting region. Figure 2 The middle figure in Figure 2 is the design of the extended electrode pattern strategy. That is, compared with Figure 2 the ordinary electrode design in the left figure in

[0056] where the electrode in the left figure in

[0057] completely matches the size of the target assembly pattern, the electrode design of the present invention is: the length of the electrode in the grid > the length of the target assembly pattern;

[0058] Example 1

[0059] (1) The electro-microfluidic driving panel includes an electrode layer and an emulsion layer:

[0060] The electrode layer is a planar electrode with a patterned electrode array, which is processed from ITO glass through photolithography and etching processes, and its surface is modified by a hydrophobic coating. The specific treatment method is: spin-coat Hyflon on the electrode surface, and then use oxygen plasma treatment to increase the adhesion between Hyflon and the photoresist layer. Further, use photolithography to pattern the photoresist on the top layer of Hyflon.

[0061] This planar electrode panel includes three rows and four columns of patterned electrode units, which are respectively composed of a pair of nearly parallel discrete double-line electrodes to form electrode patterns "S", "C", "N", "U" (such as Figure 4 the right figure in

[0062] A pair of discrete biwire electrodes are connected to the signal terminal and the ground terminal respectively, and the electrode units in each row connected to the signal terminal or the ground terminal are interconnected. Each electrode unit is isolated in a square cell grid with a side length of 350μm. The grid is made of SU-8 material and the height of the cell grid is 100-150μm.

[0063] The emulsion layer is in contact with the electrode layer. The emulsion system is a silicone oil-in-water system, with surfactant KF-6017 (PEG-10 polydimethylsiloxane, 0.5%, v / v) added to the silicone oil. The aqueous phase is deionized water, containing 8 wt% polystyrene microspheres with a diameter of 4 μm, and the volume of the aqueous phase is 20% of the silicone oil. The emulsion is mechanically emulsified to form water-in-oil droplets with an aqueous inner phase. The emulsion is then added dropwise to a polymer mesh using a pipette. After screening through the mesh, the droplet size is less than 100 μm. In this emulsion system, the aqueous droplets are subjected to positive dielectric electrophoresis, while the polystyrene microspheres are subjected to negative dielectric electrophoresis. The density of the polystyrene microspheres is higher than that of the emulsion inner phase. The emulsion is then used to wet and fill the SU-8 grid.

[0064] (2) The assembly structure of particles inside the droplet is controlled using the above-mentioned electro-microfluidic drive panel, and the specific method is as follows:

[0065] (i) An alternating current AC1 is applied to the electrodes in the electro-microfluidic drive panel to induce the fusion of intraphase droplets in the emulsion system. The AC1 frequency is 200 kHz, and the amplitude is greater than 80 Vpp and less than 200 Vpp. The amplitude is adjusted from low to high until the droplets in the unit grid almost fuse into a single large droplet. After fusion, the size of the intraphase droplet is approximately 350 μm.

[0066] (ii) An alternating current AC2 with a frequency of 400 kHz and an amplitude of 12 Vpp is applied to the electrodes in the electro-microfluidic drive panel. After the electric field is applied, a non-uniform electric field is formed between the discrete bilinear electrodes. Under the action of positive permittivity, the droplets in the emulsion automatically align with the high field strength region in the unit grid. With the assistance of the confinement effect of the space enclosed by the unit grid, the field strength inside the droplets is significantly enhanced. The droplets undergo slight deformation under the action of dielectric wetting, and the wetting area between the droplets and the electrode surface increases. At the same time, the particles are subjected to negative permittivity under the action of the electric field, avoid the position movement of the bilinear gap of the electrode pattern, and assemble under the action of the electric dipole moment of the adjacent particles.

[0067] The particle assembly structure was observed using an optical microscope, as shown in the top-down photograph. Figure 4As shown in the middle left figure, after applying alternating current AC2, the assembly morphology of polystyrene microspheres within the inner phase droplet undergoes significant changes. Particles deposited at the bottom of the droplet, driven by the panel, assemble into structures corresponding to different electrode patterns through an electric field. Furthermore, the use of an extended electrode pattern strategy optimizes the pattern defects caused by low electric field strength at the droplet edge. The assembled patterns are similar to the electrode design, achieving particle assembly patterns of "S", "C", "N", and "U" that match the ideal pattern.

[0068] Example 2

[0069] (1) The electro-microfluidic drive panel is the same as in embodiment 1 (1), except that the planar electrode panel includes three rows and four columns of patterned electrode units, each composed of a pair of nearly parallel discrete bilinear electrodes forming an electrode pattern of numerical operation symbols “1”, “+”, “1”, and “=", and the length of the pattern formed by the bilinear electrodes is greater than the length of the target assembly pattern (e.g., Figure 5 (Right image in the middle)

[0070] (2) The method of using the above-mentioned electro-microfluidic drive panel to control the assembly structure of particles inside the droplet, as well as the frequency and amplitude of the applied AC electric field, are the same as in Example 1.

[0071] The particle assembly structure was observed using an optical microscope, as shown in the top-down photograph. Figure 4 As shown in the middle left figure, the assembly morphology of polystyrene microspheres in the inner phase droplet undergoes significant changes. The particles deposited at the bottom of the droplet are assembled into a "1+1=" structure that matches the ideal pattern by means of an electric field under the drive of the panel.

[0072] Example 3

[0073] (1) The electro-microfluidic driving panel is the same as in Embodiment 1, except that the planar electrode panel includes two rows and four columns of patterned electrode units, each consisting of a pair of nearly parallel discrete bilinear electrodes forming triangular and circular electrode patterns, and the length of the pattern formed by the bilinear electrodes is greater than the length of the target assembly pattern (e.g., ...). Figure 5 (Right image in the middle)

[0074] (2) The method of using the above-mentioned electro-microfluidic drive panel to control the assembly structure of particles inside the droplet, as well as the frequency and amplitude of the applied AC electric field, are the same as in Example 1.

[0075] The particle assembly structure was observed using an optical microscope, as shown in the top-down photograph. Figure 5 As shown in the middle left figure, the assembly morphology of polystyrene microspheres in the inner phase droplet undergoes significant changes. The particles deposited at the bottom of the droplet are assembled into corresponding triangular and circular assembly pattern arrays by an electric field driven by the panel.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An electro - microfluidic driving panel, the electro - microfluidic driving panel comprising an electrode layer and an emulsion layer; The electrode layer is a planar electrode with a patterned electrode array, wherein, The patterned electrode unit consists of at least a pair of discrete double - line electrodes forming an electrode pattern; the pair of discrete double - line electrodes are respectively connected to a signal terminal and a ground terminal, and the discrete double - line electrodes can form a non - uniform electric field; The emulsion layer contacts above the electrode layer. The emulsion layer includes an outer - phase liquid, inner - phase droplets surrounded by the outer - phase liquid, and particles with a solid content of more than 0.5 wt% dispersed inside the droplets. The inner - phase droplets are subjected to positive dielectrophoretic force, and the particles are particles subjected to positive or negative dielectrophoretic force; One or more of the electrode units are separated by unit walls higher than the electrode plane, enclosing a unit cell grid containing one or more of the electrode units; The double - line electrodes are a pair of discrete electrodes with two parallel or nearly parallel thin wires. The top - view of the inner - phase droplets is divided into a wetting region and a non - wetting region. The electrode line width in the wetting region is w1, and the parallel double - line gap is g; the electrodes covered in the non - wetting region are: double - line electrode gap < g or double - line electrode line width > w1, or double - line electrode gap < g and double - line electrode line width > w1; In the electrode unit, the sum w2 of the width of the discrete double - line electrodes and the gap between them ranges from 0.1 - 3000 μm; w1 satisfies: 0.05 μm < w1 < w2 / 3, and g satisfies: 0.05 μm < g < w2 / 3; w1 is 8 - 20 μm; g is 1 - 50 μm; The bottom surface of the unit cell grid contacting the electrode layer is square, and the side length of the square ranges from 200 - 3000 μm; taking the side length of the bottom - surface square as the width and the height of the unit cell grid as the height, its aspect ratio is 1:1 ~ 5; and / or The unit walls are made of polymer grid materials, photoresists or other materials capable of forming micron - sized cell materials; the unit cell grid is covered with an upper cover plate; In the emulsion layer, the inner - phase droplets use a medium with a relatively high dielectric constant and a relatively low conductivity compared to the outer - phase. The particles are hydrophilic to the inner - phase and hydrophobic to the outer - phase, such that more than 50% of the droplet particles are dispersed in the internal space of the inner - phase droplets; the conductivity or dielectric constant of the particles is less than that of the inner - phase liquid; the particle density is relatively high compared to the density of the inner - phase of the emulsion.

2. The electro-microfluidic drive panel according to claim 1, characterized in that, The range of w2 is 1 - 500 μm.

3. The electro-microfluidic drive panel according to claim 1, characterized in that, The range of w2 is 1 - 150 μm.

4. The electro-microfluidic drive panel according to claim 1, characterized in that, The range of w2 is 40 - 60 μm.

5. The electro-microfluidic drive panel according to claim 1, characterized in that, w1 is 15 μm.

6. The electro-microfluidic drive panel according to claim 1, characterized in that... g is 10 - 30 μm.

7. The electro-microfluidic drive panel according to claim 1, characterized in that, The side length of the square ranges from 350 μm.

8. The electro-microfluidic drive panel according to claim 1, characterized in that, Taking the side length of the bottom - surface square as the width and the height of the unit cell grid as the height, its aspect ratio is 1:1 ~ 3.

5.

9. The electro-microfluidic drive panel according to claim 1, characterized in that, Taking the side length of the bottom - surface square as the width and the height of the unit cell grid as the height, its aspect ratio is 1:2.

3.

10. The electro-microfluidic driving panel according to claim 1, characterized in that, In the emulsion layer, at least one electrode unit corresponds to a single droplet; and / or After the inner - phase droplets merge, when observed from a plane perpendicular to the electrode array, the equator of the inner - phase droplets is tangent to the side length of the unit cell wall; and / or The electrode units form the same or different electrode patterns; and / or Adjacent electrode units applying the same signal are connected to each other or exist independently.

11. The electro-microfluidic drive panel according to claim 1, characterized in that, The electrode layer consists of a conductive coating on a solid substrate, including indium tin oxide glass, gold-plated glass, and copper-plated printed circuit board; the electrode pattern is formed by photolithography, soft photolithography, laser engraving, 3D printing, and screen printing of the conductive coating. The electrode layer surface is modified, and the modification treatment includes: surface treatment with dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, or modification by plasma cleaning, spin coating of thin film material, or vapor deposition.

12. The electro-microfluidic drive panel according to claim 11, characterized in that, The electrode layer is obtained by photolithography and etching of indium tin oxide glass to form a patterned electrode array.

13. The electro-microfluidic drive panel according to claim 1, characterized in that, The emulsion layer is selected from water-in-oil systems, oil-in-water systems, aqueous two-phase systems, and oil two-phase systems; and / or In the emulsion layer, the diameter of the inner phase droplets is in the range of 1-3000 μm; the diameter of the particles inside the droplets is smaller than that of the inner phase droplets, in the range of 0.1-100 μm; and / or The emulsion is formed using chip microfluidics, capillary microfluidics, mechanical emulsification, ultrasonication, thin film emulsification, or colloid milling. The internal phase droplets enter the cell grid based on gravity or the difference in wettability between the internal and external phases and the surface.

14. The electro-microfluidic drive panel according to claim 13, characterized in that, In the emulsion layer, the diameter of the inner phase droplets is 1-500 μm; the diameter of the particles inside the droplets is 0.1-10 μm.

15. The electro-microfluidic drive panel according to claim 13, characterized in that, In the emulsion layer, the diameter of the inner phase droplets is 1-100 μm; the diameter of the particles inside the droplets is 4 μm.

16. The electro-microfluidic drive panel according to claim 1, characterized in that, The particles exhibit an affinity for the inner phase and a sparseness for the outer phase, resulting in >95% of the droplet particles being dispersed within the inner phase droplet space.

17. The electro-microfluidic drive panel according to claim 1, characterized in that, In the emulsion layer, the external phase is a medium that is incompatible or poorly miscible with the internal phase droplets, or a mixture of the medium and a surfactant; the medium is one or more selected from silicone oil, hexadecane, olive oil, and mineral oil; the surfactant is one or more selected from KF-6017, MC-215, ES-5300, and ES-5612; and / or The inner phase of the emulsion is an aqueous medium selected from deionized water, or a mixture of deionized water and the following inner phase additives: polyethylene glycol diacrylate, dye, surfactant, sucrose or glucose, at a concentration of 10% in water. -1 mol / L NaCl or KCl; a biological fluid selected from low-salt buffer, plasma, or protein solution; a high dielectric constant polar solvent immiscible with the external phase, including acetamide, diphenylamine, or docosane; and / or The volume ratio of the external phase to the internal phase of the emulsion is in the range of 5-40%; the ratio of the total mass of particles to the mass of the internal phase of the emulsion is in the range of 0.1-30%.

18. The electro-microfluidic drive panel according to claim 17, characterized in that, In the emulsion layer, the external phase liquid is a mixture of silicone oil and surfactant, wherein the surfactant is selected from one or more of KF-6017, MC-215, ES-5300, and ES-5612; the internal phase of the emulsion is water, and the particles dispersed inside the droplets are selected from one or more of polystyrene particles, silica particles, yeast cells, and chlorite particles.

19. The electro-microfluidic drive panel according to claim 17, characterized in that, The particles dispersed inside the droplets are polystyrene particles.

20. A method for assembling a controllable particle structure within a droplet based on the electro-microfluidic driven panel according to any one of claims 1 to 19: S1: Apply alternating current AC1 to the patterned electrode array to control the fusion of internal phase droplets in the unit grid to form a uniform droplet array; S2: Apply AC2 to the patterned electrode array to generate a local electric field distribution that matches the electrode pattern. The particles in the inner phase droplet form chains under the interaction of dipole moments and are subjected to positive or negative permittivity, moving closer to or away from the electrode pattern, thereby controlling the assembly structure and position of the internal particles. In step S2, when using particles subjected to negative dielectric force, as the electric field strength increases, the position of the assembled structure gradually moves from the bottom of the droplet to the top of the droplet, and the assembled pattern has an enlarged size effect when viewed from a top-down perspective. and In step S1, the frequency range of the applied alternating current AC1 is 1-1000 kHz, and the amplitude range is 20-600 Vpp; In step S2, the frequency range of the applied alternating current AC2 is f > 20kHz, and the amplitude range is 1-200 Vpp.

21. The method according to claim 20, characterized in that, The shape and position of the particle assembly structure can be changed by adjusting the electric field strength and frequency.

22. The method according to claim 21, characterized in that, In step S2, when an alternating current is applied, when the particles are subjected to a positive permittivity force, the particles move towards the high field strength distribution area and assemble, forming a "light-shielding" particle assembly pattern in the area corresponding to the electrode; when the particles are subjected to a negative permittivity force, the particles move towards the low field strength distribution area and assemble, forming a "light-transmitting" particle assembly pattern in the area corresponding to the electrode. AC1 has a frequency of 200 kHz and an amplitude range of 80 Vpp-200 Vpp; AC2 has a frequency of 400 kHz and an amplitude of 12 Vpp.

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