Photoelectric wetting liquid drop control chip based on high-dielectric-constant multilayer dielectric stack structure

Abstract

The invention belongs to the technical field of photoelectric wetting liquid drop control chips, and particularly relates to a photoelectric wetting liquid drop control chip based on a high-dielectric-constant multi-layer dielectric stack structure, which comprises a bottom substrate and a top substrate, and a first transparent conductive layer, a light guide layer, a second composite dielectric layer and a second hydrophobic layer are sequentially arranged at the top of the bottom substrate. A second transparent conductive layer, a first composite dielectric layer and a first hydrophobic layer are sequentially arranged at the bottom of the top substrate; a continuous phase is filled between the first hydrophobic layer and the second hydrophobic layer, micro-droplets are dropped into the continuous phase, and micro-channel supporting structures are arranged between the first hydrophobic layer and the second hydrophobic layer and located on the two sides of the continuous phase; an alternating current power supply is connected between the first transparent conductive layer and the second transparent conductive layer; and the composite dielectric layer is formed by alternately stacking a plurality of high-dielectric-constant and low-dielectric-constant materials.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric wetting droplet manipulation chip technology, and particularly relates to a photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure. Background Technology

[0002] Photoelectric wetting droplet manipulation chips are widely used in fields such as biological detection and chemical synthesis due to their advantage of precisely controlling microdroplets. However, most existing chips use a single-layer dielectric structure, which has limited electric field control capability and insufficient breakdown resistance, resulting in low droplet splitting accuracy and poor manipulation stability, making it difficult to meet the requirements of high-throughput and high-precision applications. At the same time, the droplet sorting, reaction and collection processes of traditional chips are not smoothly connected, which easily leads to droplet aggregation or path deviation, affecting detection and reaction efficiency and limiting their widespread use in complex experimental scenarios. Summary of the Invention

[0003] The purpose of this invention is to address the aforementioned technical problems by providing a photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure.

[0004] In view of this, the present invention provides a photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure, including a bottom substrate and a top substrate. A first transparent conductive layer, a photoconductive layer, a second composite dielectric layer, and a second hydrophobic layer are sequentially disposed on the top of the bottom substrate, and a second transparent conductive layer, a first composite dielectric layer, and a first hydrophobic layer are sequentially disposed on the bottom of the top substrate. The first hydrophobic layer and the second hydrophobic layer are filled with a continuous phase, and microdroplets are dripped into the continuous phase. Microchannel support structures are provided on both sides of the continuous phase between the two layers. An AC power source is connected between the first transparent conductive layer and the second transparent conductive layer; the composite dielectric layer is composed of multiple layers of materials with alternating high dielectric constant and low dielectric constant.

[0005] Preferably, the bottom substrate and the top substrate are made of silicon or glass transparent materials, and the transparent conductive layer is made of transparent conductive oxide material.

[0006] Preferably, the conductive oxide material is ITO, and the photoconductive layer modulates the electric field intensity through the photoelectric effect to control the droplet behavior.

[0007] Preferably, the first and second hydrophobic layers are made of low surface energy materials, the continuous phase is an oil phase, and the microdroplets are an aqueous phase or a liquid containing cells / reactants.

[0008] Preferably, the chip has at least two injection holes and two outlet holes. The injection holes are used to inject microdroplets and reactant liquids, and the outlet holes are used to discharge the droplets after the reaction.

[0009] Preferably, the injection port includes a first injection port for injecting single-cell droplets and a second injection port for injecting reactant droplets, and the outlet port includes a first outlet port for discharging detection droplets and a second outlet port for discharging waste droplets.

[0010] Preferably, the chip is divided into a droplet sorting region and a droplet reaction region. The droplet sorting region controls droplet splitting through an electric field, while the droplet reaction region realizes droplet mixing and chemical reaction.

[0011] Preferably, the high dielectric constant multilayer dielectric stack structure is composed of at least three dielectric layers stacked together, which has both high electric field control capability and breakdown resistance.

[0012] Preferably, the electric field strength and frequency of the AC power supply are adjustable to precisely control the degree of droplet splitting, trajectory, and reaction process.

[0013] Preferably, it can realize the parallel splitting and manipulation of multiple droplets, adapt to the high-throughput droplet manipulation requirements, and the droplet size and position control accuracy is ≤100μm.

[0014] Preferably, it also includes the process used to manufacture the chip: Specifically, the steps include the following: Step S11: Substrate cleaning. Select silicon or glass transparent material as the bottom substrate and top substrate, and clean them sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning, and then remove surface organic contaminants by oxygen plasma bombardment. Step S12: Preparation of transparent conductive layer: A transparent conductive oxide thin film is deposited on the cleaned substrate surface by magnetron sputtering process to form a first transparent conductive layer and a second transparent conductive layer. Step S13: Photoconductive layer preparation, a photoconductive material thin film is deposited only on the surface of the first transparent conductive layer of the bottom substrate using plasma-enhanced chemical vapor deposition. Step S14: Composite dielectric layer preparation: High dielectric constant material and low dielectric constant material are alternately deposited on the surface of the photoconductive layer and the surface of the second transparent conductive layer by plasma-enhanced chemical vapor deposition, atomic layer deposition or magnetron sputtering process to form at least two alternately stacked composite dielectric layers. Step S15: Preparation of hydrophobic layer: A low surface energy fluoropolymer solution is spin-coated onto the surfaces of the two composite dielectric layers, and then baked to form the first hydrophobic layer and the second hydrophobic layer. Step S16: Fabrication of microchannel support structure: Photoresist is patterned on the surface of the bottom or top substrate using photolithography to form microchannel walls and support pillars; Step S17: Bonding and packaging. The bottom substrate assembly and the top substrate assembly are aligned and bonded together using a microfluidic support structure. The chip edges are then sealed twice. Step S18: Channel fabrication. At least two injection holes and two outlet holes are fabricated at preset positions on the chip. The injection holes are used to inject microdroplets and reactant liquids, and the outlet holes are used to discharge the droplets after the reaction.

[0015] The beneficial effects of this invention are as follows: By employing a composite dielectric layer structure with alternating stacks of high- and low-dielectric-constant materials, the electric field control capability and breakdown resistance are significantly improved. Combined with the photoelectric effect modulation of the photoconductive layer, a dual improvement in droplet splitting accuracy and manipulation stability is achieved. The droplet size and position control accuracy can reach within 100 μm, effectively solving the problems of insufficient manipulation accuracy and poor stability inherent in traditional single-layer dielectric structure chips. Simultaneously, the optimized design of the multi-layer dielectric stack structure supports parallel splitting and manipulation of multiple droplets, significantly improving the chip's high-throughput processing capability and adapting to the large-scale application needs of scenarios such as biological detection and chemical synthesis.

[0016] By rationally dividing functional areas such as droplet sorting and reaction zones, and combining them with a multi-injection-outlet design and microfluidic support structure, the chip achieves a seamless connection between droplet injection, sorting, splitting, reaction, and output, effectively avoiding problems such as droplet aggregation and path deviation. The adjustable design of the electric field strength and frequency not only ensures the efficiency and precision of the droplet reaction process but also adapts to the manipulation needs of droplets with different properties (aqueous phase, oil phase) and different sizes, broadening the chip's application scenarios and providing reliable technical support for complex experimental procedures. Attached Figure Description

[0017] Figure 1 This is a schematic diagram (side view) of the enhanced photoelectric wetting droplet manipulation chip structure based on a high dielectric constant multilayer dielectric stack structure of the present invention. Figure 2 This is a schematic diagram (side view) of the high dielectric constant multilayer dielectric stack structure of the present invention. Figure 3 This is a schematic diagram (top view) illustrating how the chip of this invention manipulates droplets. Figure 4 This is a flowchart illustrating the workflow for analyzing single-cell samples in this invention. Figure 5 This is an optical diagram illustrating the photoelectric wetting of droplets and simultaneous manipulation of droplets and internal microparticles in this invention.

[0018] Figure 6 The simulated thermal diagram shows the relationship between the manipulated electric field strength and frequency and the contact angle of the droplet surface in this invention.

[0019] Figure 7This is a comparison of the breakdown voltage and driving voltage performance of different dielectric layer structures under equivalent total thickness in embodiments of the present invention. In the figure: 1, bottom substrate; 2, first transparent conductive layer; 21, second transparent conductive layer; 3, photoconductive layer; 4, first composite dielectric layer; 41, second composite dielectric layer; 5, top substrate; 6, first hydrophobic layer; 61, second hydrophobic layer; 7, continuous phase; 8, microdroplet; 9, microchannel support structure; 10. First injection hole; 11. Second injection hole; 12. First outlet hole; 13. Second outlet hole; 14. Support structure; 15. Isolation structure; 16. Droplet sorting zone; 17. Droplet reaction zone; 18. Droplet containing reactant; 19. Merged microdroplet; 20. Target droplet containing single cell; 22. Waste microdroplet. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0021] like Figure 1 The diagram illustrates the structure of the enhanced photoelectric wetting droplet manipulation chip based on a high-dielectric-constant multilayer dielectric stack structure of this invention. Specifically, it includes a bottom substrate 1, typically using silicon or glass as a support layer to provide the basic support for the chip. Transparent conductive layers 2 and 21, made of transparent conductive oxides such as ITO, serve as electrode layers, allowing light to reach the chip surface while simultaneously controlling the electric field. A photoconductive layer 3, located above the transparent conductive layers, guides the transmission of the light source and modulates the electric field intensity through the photoelectric effect, thereby controlling the droplet behavior. Composite dielectric layers 4 and 41, composed of alternating layers of high-dielectric-constant and low-dielectric-constant materials, are the key structure of this invention, providing strong electric field control capabilities and breakdown resistance. The top substrate 5, typically a transparent material, is connected to the bottom substrate via dielectric layers to complete the chip packaging.

[0022] A first transparent conductive layer 2 and a second transparent conductive layer 21 are respectively disposed on the top of the bottom substrate 1 and the bottom of the top substrate 5. A light guide layer 3 is disposed on the top of the first transparent conductive layer 2. A first composite dielectric layer 4 is disposed on the bottom of the second transparent conductive layer 21. A second composite dielectric layer 41 is disposed on the top of the light guide layer 3. A first hydrophobic layer 6 and a second hydrophobic layer 61 are respectively disposed on the bottom of the first composite dielectric layer 4 and the top of the second composite dielectric layer 41. A continuous phase 7 is filled between the first hydrophobic layer 6 and the second hydrophobic layer 61, and microdroplets 8 are dropped into the continuous phase 7. A microchannel support structure 9 is disposed between the first hydrophobic layer 6 and the second hydrophobic layer 61 and on both sides of the continuous phase 7. An AC power supply is connected between the first transparent conductive layer 2 and the second transparent conductive layer 21.

[0023] The preparation process of the present invention specifically includes the following steps: Step 1: Substrate cleaning. Glass with a thickness of 500-700 micrometers is selected as the bottom substrate 1 and the top substrate 5. Acetone, isoacetone and deionized water are used for ultrasonic cleaning in sequence, and oxygen plasma bombardment treatment is performed to remove surface organic contaminants.

[0024] Step 2: Preparation of transparent conductive layers 2 and 21. Indium tin oxide (ITO) thin films are deposited on the cleaned substrate surface using magnetron sputtering. The thickness is controlled at 100-200 nm, and the sheet resistance is controlled at 10-20 Ω / sq. These layers serve as the common ground electrode and driving electrode of the chip.

[0025] Step 3: Fabrication of photoconductive layer 3 (bottom layer only). On the ITO surface of the bottom substrate, a hydrogenated amorphous silicon a-Si:H thin film is deposited using plasma-enhanced chemical vapor deposition (PECVD) at a deposition temperature of 200-300℃, with a thickness of 1 micrometer. This layer serves as a photosensitive switch, and its dark conductivity needs to be below 10⁻⁶ S / m.

[0026] Step 4: Key process for preparing composite dielectric layers 4 and 41, using plasma-enhanced chemical vapor deposition (PECVD) to alternately deposit high / low dielectric constant materials.

[0027] Step A: Deposit the first layer of high dielectric constant material, with a thickness of 50-100 nanometers; Step B: Deposit the first layer of low dielectric constant material, 20-50 nanometers thick, to repair pinhole defects in the underlying layer; Step C: Repeat steps A and B for at least one cycle to form a dense, layered structure.

[0028] Step 5: Preparation of hydrophobic layers 6 and 61. A fluoropolymer solution such as Teflon AF1600 or Cytop is spin-coated onto the surface of the composite dielectric layer at a spin speed of 1500 rpm. The solvent is then removed by baking at 120°C to form a hydrophobic film with a thickness of about 50-100 nanometers and an initial contact angle greater than 100°.

[0029] Step 6: Fabrication of microchannel support structure 9. Dry film photoresist or SU-8 negative photoresist is attached to the surface of the bottom or top chip. Microchannel walls and support pillars are formed by exposure, development and patterning through photolithography. The height, i.e. the thickness of the liquid layer, is controlled between 50 micrometers and 300 micrometers.

[0030] Step 7: The bottom substrate assembly and the top substrate assembly are aligned and bonded or pressed together using the microchannel support structure 9. The microchannel support structure 9 not only serves as the sidewall boundary between the continuous phase 7 and the microdroplets 8, but also acts as a spacer, precisely defining the gap height between the upper and lower plates.

[0031] In a preferred encapsulation embodiment, the microfluidic support structure 9 uses double-sided adhesive tape such as 3MVHB tape or photosensitive dry film. After alignment, the bottom layer and the other layers are sealed together by thermo-press bonding to form a closed microfluidic cavity.

[0032] UV-curable adhesive can be applied to the edges of the chip for secondary sealing to prevent leakage of the continuous phase.

[0033] Step 8: The first hydrophobic layer 6 and the second hydrophobic layer 61 mainly serve two functions in the chip: The first provides a larger initial contact angle, and according to the Young-Lippmann equation, the photoelectric wetting effect depends on the decrease in contact angle after the voltage is applied.

[0034] The hydrophobic layer allows the microdroplet 9 to maintain a contracted spherical contact angle greater than 110° in the unelectrified state, thereby generating a sufficiently large contact angle change difference when pressure is applied by light, generating a stronger electrowetting driving force, making it easier for the droplet to displace or break apart.

[0035] To reduce contact hysteresis and prevent adhesion, hydrophobic layers typically have extremely low surface energy, which can significantly reduce the contact hysteresis of microdroplets, especially those containing biological proteins or cells, during their movement. This reduces non-specific adsorption of droplets on the dielectric layer surface, prevents pinning effects, and ensures the fluidity and reversibility of droplet movement.

[0036] like Figure 2The diagram shows a schematic of the high-dielectric-constant multilayer dielectric stack structure of the present invention, which is formed by stacking multiple dielectric layers. Regarding the stacking method: the composite dielectric layer 4 or 41 is not a simple thickening of a single material, but rather a periodic heterogeneous structure formed using an alternating deposition process. Specifically, on the surface of the photoconductive layer 3 or the transparent conductive layer 21, a high-dielectric-constant material thin film (High-k layer) is first deposited using plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), or magnetron sputtering. Immediately following, a low-dielectric-constant material thin film (Low-k layer) is deposited in situ on its surface. This utilizes the mismatch in the lattice structures of the different materials to interrupt the continuous growth of the grains. Regarding the number of layers: the multilayer dielectric stack structure contains at least two sub-dielectric layers, i.e., one high-k layer + one low-k layer, but preferably an odd-numbered layer structure of three or more layers, such as High-k / Low-k / High-k. In the preferred embodiment, the number of layers is suggested to be between 3 and 10 layers. Rationale for Layer Number Design: Too few layers, such as 2 layers, cannot completely avoid the risk of pinhole defects penetrating through; while too many layers, such as >20 layers, increase process complexity and internal stress, leading to film peeling. Regarding Connections and Interfaces: Each sub-dielectric layer is tightly bonded to the others through van der Waals forces or covalent bonds, forming a physically seamless stack, equivalent in electrical characteristics to multiple series capacitors. Interface connections exist between adjacent dielectric layers. The low-k dielectric layer acts as a defect-blocking layer, filling or covering any micropores or grain boundary defects that may occur on the surface of the high-k dielectric layer below, cutting off the vertical conduction path of leakage current. Overall connection: the bottom of the entire multilayer dielectric stack structure is in direct contact and electrically coupled to the photoconductive layer 3 or the transparent conductive layer 21, while the top is chemically bonded or physically attached to the hydrophobic layer 6 or 61.

[0037] like Figure 3The diagram shows a schematic of the chip's operation of manipulating droplets. The chip's operation can be divided into the following steps to ensure that droplets can be precisely manipulated, split, and merged: Initialization Sample Injection: First, a discrete phase liquid containing the target to be detected, such as a single cell, is injected into the droplet sorting area 16 of the chip using the first injection port 10. At this time, the flow rate can be controlled by an external pump, and with the electrowetting force generated by the photoconductive layer 3, uniform sample microdroplets 8 are generated and lined up. Reagent Addition Reactant Injection: After the target droplet is sorted and moves to the droplet reaction area 17, reactant droplets, such as lysis buffer, fluorescent probe, or drug, are injected through the second injection port 11 according to the reaction requirements. The injection timing of the first injection port 10 and the second injection port 11 can be synchronous for immediate mixing or asynchronous sequential for multi-step reactions, controlled by an external micro-injection pump in conjunction with the photoelectric addressing signal on the chip. Droplet Sorting: Droplets enter the droplet sorting area 16 of the chip through the first injection port 10. The behavior of the droplets in this area is controlled by an electric field. The composite dielectric layers 4 and 41 of the chip provide a uniform electric field, enabling precise manipulation of the droplet within this region. The droplet enters the droplet sorting region 16 of the chip as shown... Figure 3 As shown. Although not visible from the top view, the bottom of this area is actually formed by... Figure 1 The substrate 1, photoconductive layer 3, and second composite dielectric layer 41 shown are collectively constituted. During the sorting process, the light pattern is projected onto the photoconductive layer 3, causing the AC voltage to primarily drop onto the second composite dielectric layer 41. This is due to the high / low dielectric constant alternating stacking structure employed in the composite dielectric layer 41. Figure 2 As shown, this region can withstand high-frequency optical switching without charge trapping or dielectric breakdown, thus providing stable and uniform electrowetting force for high-speed droplet sorting (>10 drops / second). Droplet splitting and manipulation: Changes in electric field strength and frequency can effectively control the degree of droplet splitting, producing smaller droplets. Under the action of the electric field, the droplet will precisely control its splitting into smaller droplets according to changes in the intensity and frequency of the electric field. Through optimization of the multilayer dielectric stack structure, the droplet splitting process is more stable and precise. This chip can realize the parallel splitting of multiple droplets, adapting to high-throughput operation requirements. Droplet splitting and manipulation are achieved through electric field adjustment, ensuring that the size and position of each droplet can be precisely controlled. Increasing the AC voltage amplitude from the holding voltage (e.g., 10Vrms) to the splitting voltage (e.g., 20Vrms) generates a strong electrowetting force in the composite dielectric layers 4 and 41, significantly reducing the droplet contact angle (e.g., from 115° to 65°), elongating the droplet into a dumbbell shape.

[0038] like Figure 6The figure shows a simulated thermal diagram of the effective potential difference distribution under different driving frequencies and voltage amplitudes in an embodiment of the present invention. The colors in the figure, from white to dark blue, represent the effective potential difference ΔV gradually increasing from 5.00V to 13.00V. ΔV represents the difference in voltage drop between the illuminated and unilluminated areas on the composite dielectric layer. A larger value indicates a stronger photoinduced dielectric wetting force and a greater change in the droplet contact angle. Combined with... Figure 6 The control strategy for achieving fine droplet splitting in this invention is as follows: a high-frequency / low-frequency modulation mechanism, from... Figure 6 As can be seen, with the same voltage amplitude and the X-axis fixed, the effective potential difference ΔV increases significantly and the color deepens as the frequency decreases and the Y-axis descends. This is because the photoconductive layer a-Si:H exhibits better conductivity at low frequencies, allowing more voltage to be distributed across the composite dielectric layer. During the splitting initiation stage, when the droplet surface tension needs to be overcome for splitting, the control system lowers the frequency to the dark blue area in the 40kHz-80kHz range. At this point, ΔV reaches a peak value >11V, generating a strong tensile force sufficient to overcome the Laplace pressure, causing the mother droplet to be rapidly elongated and necked. During the fine-forming stage, when the droplet neck is about to break, to avoid generating unstable satellite droplets, the frequency can be finely adjusted to the light blue area in the 100kHz-140kHz range, appropriately reducing the electrowetting force and achieving a soft-landing, gentle breakage. To generate micron-sized fine sub-droplets such as <100nL, extremely high shear forces are required. Figure 6 This indicates that at the operating point of 20V 40kHz, ΔV reaches its maximum value of approximately 13V. The high dielectric constant multilayer dielectric stack structure of this invention is designed to support this high-voltage, low-frequency, high-strength operating condition, ensuring that dielectric breakdown does not occur while generating maximum splitting force. In summary, Figure 6 This invention confirms that by coordinating the voltage (12V-20V) and frequency (40kHz-200kHz) of the AC power supply, it can precisely modulate the magnitude of the electrowetting force within a wide operating window, thereby achieving precise control of the droplet splitting process and obtaining uniformly sized fine microdroplets.

[0039] Droplet reaction: After splitting, the droplets enter the droplet reaction region 17 of the chip, where they mix or react chemically with other reactants. Within this region, the chip precisely controls the electric field to ensure stable droplet reaction and performs reactant analysis or processing as needed. This process utilizes the electric field to regulate droplet movement, ensuring both efficiency and accuracy in the reaction process.

[0040] Droplet Output and Collection: After the reaction and detection are completed, the target droplets are guided by the light pattern generated by the photoconductive layer 3 and precisely delivered along the microchannel to the second outlet 13 for discharge from the chip, where they are used for subsequent offline analysis such as gene sequencing or storage. Non-target droplets identified as empty or multi-celled droplets during the sorting stage are guided to the first outlet 12 and discharged as waste. This output process is entirely driven by the chip's photoinduced dielectric wetting force, requiring no external mechanical valves. Specifically, only the second outlet 13 is configured as an interface with subsequent high-value experimental steps, ensuring high-purity sample recovery.

[0041] like Figure 4 The diagram shows the complete workflow of single-cell analysis based on this chip, which includes the following five stages: Stage 1: Initialization and Sample Injection. The continuous phase 7 (oil phase) fills the chip microchannels, and then the dispersed phase containing cell suspension is injected through the first injection hole 10. Stage 2: Droplet Recognition and Addressing. Combined with an external optical imaging system such as a microscope and a high-speed camera, the microdroplets 8 flowing through the detection area are identified in real time. The algorithm determines the number of cells encapsulated in the droplet: 0, 1, or >1. Path A is not the target. If it is determined to be an empty droplet or a multi-cell droplet, the light pattern controls its movement along the bypass and directly guides it to the first outlet hole 12 for discharge. Path B is the target. If it is determined to be a single-cell droplet, the system plans a path to guide it to the droplet reaction area 17. Stage 3: Droplet Sorting and Path Planning. Under the action of photoinduced dielectrophoresis, the target single-cell droplet passes through the slits on the physical barrier or virtual photoelectric barrier of the isolation structure 15 and enters the relatively independent reaction area, avoiding cross-contamination with the waste liquid channel. Phase four involves droplet arraying and reaction arraying. Single-cell droplets entering the reaction zone are guided to preset array sites for anchoring. Reagent injection involves injecting microdroplets 8 containing reaction reagents, such as lysis buffer or fluorescent substrates, as needed through the second injection port 11. Droplet fusion is then performed, controlling the one-to-one fusion of reagent droplets and single-cell droplets at the array sites to initiate the biochemical reaction. Phase five involves detection and export. After the reaction is complete, the optical system detects the fluorescence signal of the fused droplets. Valid positive droplets are unlocked and moved, ultimately being removed from the chip via the second exit port 13 for collection.

[0042] like Figure 5 The image shown is an optical micrograph of a droplet photoelectric wetting manipulator using this chip in an embodiment of the present invention, demonstrating the chip's excellent manipulation performance: a) precise droplet transport is shown. Figure 5 a shows the process of enriching micron-sized particles in a nanoliter (nL) microdroplet driven by bright stripes of an optical pattern. The timing diagrams from left to right show that by switching the manipulation frequency, the optical pattern controls the movement of the microspheres within the droplet to one end of the droplet. b demonstrates droplet stretching and splitting. Figure 5b demonstrates the droplet splitting process. Tensile forces are generated by applying opposing light spots to both ends of the droplet, while a dark region is applied in the middle to cleave it. Thanks to the high dielectric constant provided by the multilayer dielectric stack structure, the chip generates an electrowetting force sufficient to overcome the surface tension of the droplet under a safe voltage, successfully stretching and breaking a mother droplet into two uniformly sized sub-droplets without dielectric breakdown. c demonstrates the manipulation of microparticle cells within the droplet. Figure 5 c demonstrates the arrayed arrangement of microparticles simulating cells encapsulated within a droplet. By adjusting the illumination pattern of the photoconductive layer 3, not only can the movement of the droplet itself be controlled, but also micro-eddies or dielectric forces can be generated inside the droplet through an induced electric field, enabling the aggregation, dispersion, or specific patterning of micron-sized particles within the droplet. This demonstrates the enormous potential of this chip in single-cell sorting and analysis applications.

[0043] The light source is the key driving device for achieving pixel-free, flexible droplet manipulation in this invention. The light source projects a programmable spatiotemporal light pattern onto the photoconductive layer 3 of the chip. Utilizing the photosensitive properties of the photoconductive layer, such as a-Si:H, the impedance of the illuminated area is significantly reduced, transitioning from a high-resistivity state to a conductive state. This causes the AC voltage applied between the transparent conductive layers 2 and 21 to be primarily divided and distributed to the composite dielectric layers 4 and 41 and the hydrophobic layer. The illuminated area forms an equivalent virtual electrode on the surface of the dielectric layer, thereby generating a local high electric field at the solid-liquid interface, altering the contact angle wettability of the microdroplets 8 or generating dielectric wetting force. By changing the shape, position, and trajectory of the projected light pattern, the microdroplets 8 can be flexibly driven to move, merge, split, or mix along the optical path without the need for physical etching of electrodes. For equipment selection, the light source is preferably a digital micromirror device (DMD) projector, a liquid crystal display (LCD) projection system, or a scanning laser beam. Its output wavelength must match the absorption spectrum of the photoconductive layer 3; for example, 500nm-700nm visible light is used for amorphous silicon layers.

[0044] Traditional monolayer dielectric films (such as monolayer Si3N4 and monolayer Al2O3) inevitably accumulate penetrating pinholes and microcracks as their thickness increases. This leads to a decrease in their actual effective breakdown voltage (V). bd After reaching the 130V~150V range, it encounters a bottleneck, showing a trend of weakness or even attenuation (e.g.) Figure 7 As shown by the gentle curve in A, it is extremely prone to local avalanche breakdown under high-frequency alternating electric fields.

[0045] The composite dielectric stack used in this invention (especially the HfO2 / ZrO2 high-k stack structure) forcibly interrupts the continuous growth of defects by alternating deposition of multiple heterogeneous materials and utilizing lattice mismatch. Low-dielectric-constant layers or heterogeneous interfaces effectively block the vertical conduction path of leakage current. Therefore, with the same total thickness, the effective breakdown voltage of the multilayer stack structure exhibits a perfect linear increase with the number of layers (reaching up to over 400V), completely surpassing the physical safety limit of single-layer thick films.

[0046] While ensuring high breakdown voltage, traditional designs that simply thicken the single-layer Si3N4 dielectric layer will cause a sharp drop in the system's equivalent capacitance, forcing the illumination-dependent breakdown voltage (V) required to drive droplet deformation to decrease. op The significant increase in power consumption raises the risk of thermal breakdown of the chip and the photoconductor layer.

[0047] The preferred HfO2 / ZrO2 multilayer dielectric stack structure of this invention fully utilizes the extremely high relative permittivity of the materials (all greater than 20). For example... Figure 7 As shown in B, when achieving the same droplet target contact angle change, even when stacked to 11 layers (the total thickness is significantly increased to ensure insulation safety), the driving voltage is still firmly suppressed in the extremely low range of 14V~16V. This value is not only far lower than that of single-layer Si3N4 and Al2O3 of the same thickness, but also better than that of conventional ultra-thin dielectric layers.

[0048] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A photoelectric droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure, characterized in that: The substrate includes a bottom substrate (1) and a top substrate (5). The bottom substrate (1) is provided with a first transparent conductive layer (2), a light guide layer (3), a second composite dielectric layer (41), and a second hydrophobic layer (61) in sequence on the top. The top substrate (5) is provided with a second transparent conductive layer (21), a first composite dielectric layer (4), and a first hydrophobic layer (6) in sequence on the bottom. A continuous phase (7) is filled between the first hydrophobic layer (6) and the second hydrophobic layer (61). Microdroplets (8) are dripped into the continuous phase (7), and microchannel support structures (9) are provided on both sides of the continuous phase (7). An AC power source is connected between the first transparent conductive layer (2) and the second transparent conductive layer (21); the composite dielectric layer is composed of multiple layers of materials with high dielectric constant and low dielectric constant stacked alternately.

2. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 1, characterized in that: The bottom substrate (1) and the top substrate (5) are made of silicon or glass transparent materials, and the transparent conductive layers (2, 21) are made of transparent conductive oxide materials.

3. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 2, characterized in that: The conductive oxide material is ITO, and the photoconductive layer (3) controls the droplet behavior by adjusting the electric field strength through the photoelectric effect.

4. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 2, characterized in that: The first hydrophobic layer (6) and the second hydrophobic layer (61) are made of low surface energy materials, the continuous phase (7) is an oil phase, and the microdroplets (8) are an aqueous phase or a liquid containing cells / reactants.

5. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 1, characterized in that: The chip is provided with at least two injection holes and two outlet holes. The injection holes are used to inject microdroplets (8) and reactant liquid, and the outlet holes are used to discharge the microdroplets (8) after the reaction. The injection holes are the first injection hole (10) and the second injection hole (11), and the outlet holes are the first outlet hole (12) and the second outlet hole (13).

6. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 5, characterized in that: The first injection hole (10) is used to inject microdroplets (8) containing single cells, the second injection hole (11) is used to inject microdroplets (8) containing reactants, the first outlet hole (12) is used to discharge microdroplets (8) after detection, and the second outlet hole (13) is used to discharge waste microdroplets (8).

7. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 5, characterized in that: The chip is divided into a droplet sorting region (16) and a droplet reaction region (17). The droplet sorting region (16) controls the splitting of microdroplets (8) by electric field, and the droplet reaction region (17) realizes the mixing and chemical reaction of microdroplets (8). The high dielectric constant multilayer dielectric stack structure is made of at least three dielectric layers stacked together, which has both high electric field control capability and breakdown resistance. The electric field strength and frequency of the AC power supply are adjustable, which can be used to precisely control the degree of splitting, trajectory and reaction process of microdroplets (8); It can realize the parallel splitting and manipulation of multiple microdroplets (8), adapt to the high-throughput droplet manipulation requirements, and the size and position control accuracy of microdroplets (8) is ≤100μm.

8. The photoelectric wetting droplet manipulation chip based on a high dielectric constant multilayer dielectric stack structure according to claim 7, characterized in that: It also includes the process used to manufacture the chip. Specifically, the steps include the following: Step S11: Substrate cleaning. Select silicon or glass transparent material as the bottom substrate (1) and top substrate (5), and clean them sequentially with acetone, isopropanol and deionized water using ultrasonic cleaning, and then remove surface organic contaminants by oxygen plasma bombardment. Step S12: Preparation of transparent conductive layer. Transparent conductive oxide thin films are deposited on the cleaned bottom substrate (1) and top substrate (5) by magnetron sputtering process to form the first transparent conductive layer (2) and the second transparent conductive layer (21), respectively. Step S13: Photoconductive layer preparation. A photoconductive material thin film is deposited on the surface of the first transparent conductive layer (2) of the bottom substrate (1) using plasma-enhanced chemical vapor deposition to form a photoconductive layer (3). Step S14: Composite dielectric layer preparation. High dielectric constant material and low dielectric constant material are alternately deposited on the surface of the photoconductive layer (3) and the surface of the second transparent conductive layer (21) by plasma-enhanced chemical vapor deposition, atomic layer deposition or magnetron sputtering process to form a second composite dielectric layer (41) and a first composite dielectric layer (4), respectively. The first composite dielectric layer (4) and the second composite dielectric layer (41) are both structures with at least two layers stacked alternately. Step S15: Preparation of hydrophobic layer: Low surface energy fluoropolymer solution is spin-coated onto the surfaces of the first composite dielectric layer (4) and the second composite dielectric layer (41), respectively, and then baked to form the first hydrophobic layer (6) and the second hydrophobic layer (61). Step S16: Fabrication of microchannel support structure. Photoresist is patterned on the surface of the bottom substrate (1) or the top substrate (5) by photolithography to form a microchannel support structure (9). The microchannel support structure (9) includes microchannel walls and support pillars. Step S17: Bonding and packaging, the bottom substrate assembly and the top substrate assembly are aligned and bonded together through the microfluidic support structure (9), and the chip edge is sealed twice. Step S18: Channel processing, forming a first liquid injection hole (10), a second liquid injection hole (11), a first liquid outlet hole (12), and a second liquid outlet hole (13) at a preset position on the chip. The first liquid injection hole (10) and the second liquid injection hole (11) are used to inject microdroplets (8) and reactant liquid, and the first liquid outlet hole (12) and the second liquid outlet hole (13) are used to discharge microdroplets (8) after the reaction.

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