A preparation method of electrostatic self-assembled film and digital microfluidic chip

Abstract

The present invention relates to the field of preparation of self-assembled films, and in particular to a method for preparing an electrostatic self-assembled film and a digital microfluidic chip for implementing the method. The method for preparing an electrostatic self-assembled film comprises the following steps: 1) reagent preparation: various film-forming droplets are respectively loaded in the corresponding liquid reservoir electrode units of the digital microfluidic chip, silicone oil is taken to wrap each of the film-forming droplets, deionized water is loaded on the cleaning liquid reservoir electrode unit, and each of the liquid reservoir electrode units is pre-energized; 2) preparation and accumulation of the 1st to Nth molecular layer membranes, wherein N≥2 and is an integer, each molecular layer membrane is prepared layer by layer, and accumulated layer by layer at the hydrophilic point, thereby forming an electrostatic self-assembled film. The method and chip of the present invention can realize the rapid preparation of electrostatic self-assembled films, fully automatic control, reduce the consumption of manpower and reagents, perform high-throughput parallel synthesis of multiple electrostatic self-assembled films, and screen the synthesis conditions of electrostatic self-assembled films.

Description

Technical Field

[0001] The invention relates to the field of preparation of self-assembled films, in particular to a preparation method of an electrostatic self-assembled film and a digital microfluidic chip for realizing the method. Background Art

[0002] Electrostatic self-assembly is a method of assembling film layers at a microscale using electrostatic interaction forces. Based on the principle of electrostatic attraction and repulsion, tiny charged particles or charged polymers spontaneously form ordered structures without external action. Electrostatic self-assembled films have a wide range of applications in many fields, including materials science (such as optical materials, electronic devices, sensors, nanocatalysts, etc.), nanotechnology (such as nanoelectronics, nanophotonics, nanomechanical systems, etc.), drug delivery systems, biosensors (such as self-assembly of biomolecules, antibodies or DNA probes on the sensor surface, etc.), tissue engineering (such as construction of three-dimensional biomaterial structures), optical devices (such as gratings, optical lenses), separation and filtration membranes (such as films for bioseparation and water treatment). By precisely controlling the film assembly conditions, material selection and surface modification, the desired functions and performance can be achieved to meet the needs of specific applications.

[0003] With the development of science and technology, the demand for ordered thin film materials with specific functions is also increasing. Compared with methods such as chemical vapor deposition and molecular beam epitaxy to prepare thin films, ultra-thin films formed by self-assembly have the advantages of high order, good flatness, controllable film thickness and structure at the molecular level, and no restrictions on the shape of the substrate. In the self-assembled ultra-thin film system, by adjusting the film thickness, changing the material of the assembled film, introducing functional groups or inducing the orientation of functional groups, the self-assembled ultra-thin film can have a certain structure and function, and then study the relationship between structure and function, screen out structures with specific functions as needed, and finally realize the construction of functional devices by molecular assembly. The technology of self-assembled ultra-thin films not only has broad application prospects as a surface modification technology in realizing the specific optical, electrical, magnetic, nonlinear optical and other functions of thin films, but also has great development potential in the manufacture of extremely micro-scale devices. In the self-assembled ultra-thin film technology, the layer-by-layer electrostatic self-assembly technology has become an ideal choice for the preparation of high-quality multilayer films and molecular devices due to its simplicity and strong film stability. It has broad application prospects in many fields.

[0004] The traditional method for preparing electrostatic self-assembled films is that the substrate is pretreated to make it charged, and then immersed in a polycation solution for a period of time to grow a polycation monolayer. When the surface is saturated with polycation polymer chain deposition, the substrate is rinsed in deionized water, and then the substrate is immersed in an anionic polymer solution, and the substrate is rinsed again before returning to the cationic polymer solution. This completes a bilayer growth cycle. Such a cycle is repeated, and such a bilayer is grown layer by layer until the required film thickness is reached. However, in practical applications, since the thickness of each bilayer of the electrostatic self-assembled film is at the nanometer level, it sometimes takes a very large number of cycles to meet the demand for film thickness, which greatly limits the actual device application. And multiple cycles make the synthesis of the film extremely cumbersome, consuming a lot of time and repetitive manpower. Therefore, a preparation method that can be automated and reduce the time-consuming self-assembly is of great significance to the development of electrostatic layer-by-layer self-assembly.

[0005] Therefore, those skilled in the art are committed to developing a method for preparing an electrostatic self-assembled film with high synthesis efficiency and less time consumption, and a digital microfluidic chip that can implement the method. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a method for preparing an electrostatic self-assembled film with high synthesis efficiency and short time consumption, and a digital microfluidic chip capable of implementing the method.

[0007] To achieve the above object, the present invention provides a method for preparing an electrostatic self-assembled film, comprising the following steps:

[0008] 1) Reagent preparation: various film-forming droplets are loaded in the corresponding liquid reservoir electrode units of the digital microfluidic chip, silicone oil is used to wrap each of the film-forming droplets, deionized water is loaded in the washing liquid reservoir electrode unit, and each of the liquid reservoir electrode units is pre-energized;

[0009] 2) Preparation and accumulation of the 1st to Nth molecular layer films, wherein N ≥ 2 and is an integer: each molecular layer film is prepared layer by layer and accumulated layer by layer at the hydrophilic point to form an electrostatic self-assembled film, and the preparation of each molecular layer film includes the following steps:

[0010] 21) Preparation of the first molecular layer membrane, dispensing a first reagent droplet from the first liquid reservoir electrode unit, and transporting it to the hydrophilic point through the channel electrode, standing for more than 5 seconds, the charged substance is adsorbed to the hydrophilic site, and the droplet is moved away from the hydrophilic position by the electrowetting force to the waste liquid collection electrode unit; dispensing a cleaning liquid droplet from the cleaning liquid reservoir electrode unit, transporting it to the hydrophilic point through the channel electrode, washing away the residual reagent at the hydrophilic point, and ensuring that only a single layer with strong electrostatic attraction remains on the electrode plate;

[0011] 22) Preparation of the Nth molecular layer membrane, dispensing the Nth reagent droplet from the Nth liquid reservoir electrode unit, transporting the droplet to the hydrophilic site through the channel electrode connected thereto, and standing for more than 5 seconds, the Nth reagent droplet and the N-1th reagent droplet have opposite charges, so that the polymer or particles with opposite charges in the Nth reagent droplet are deposited on the surface of the N-1th molecular layer under the action of electrostatic force; using electrowetting force to move the droplet away from the hydrophilic position to the waste liquid collection electrode unit; after the deposition is completed, transporting the cleaning droplet to the hydrophilic point through the channel electrode, and washing away the residual reagent with the cleaning droplet;

[0012] Preferably, the separated molecular layers are prepared using droplets of the same reagent, that is, using two film-forming materials with opposite charges to prepare the electrostatic self-assembled film.

[0013] Preferably, in step 2), the reagent droplets are dispensed from the target liquid reservoir electrode unit by sequentially turning on and off the electrodes adjacent to the target liquid reservoir electrode unit.

[0014] Preferably, the film-forming droplets can be selected from one or more of polycationic or anionic electrolytes, inorganic small particles, metal colloidal particles, and biomacromolecules.

[0015] Preferably, the polycationic or anionic electrolyte may be polyaniline, nitrogen-containing polyelectrolyte polyacrylonitrile, diazo resin, polydiallyldimethylammonium chloride, sodium polystyrene sulfonate, spirooxazine dye, polyvinyl alcohol, polyvinyl sulfate, polypropylene, poly(allylamine·hydrochloric acid); the inorganic small particles are charged II-VI semiconductor material nanoparticles synthesized from any one or more of SiO2, TiO2 or CdTe, CdS, and ZnS.

[0016] The present invention also provides a digital microfluidic chip for preparing an electrostatic self-assembled film, comprising an upper electrode plate and a lower electrode plate; the upper electrode plate and a first hydrophobic layer; the lower electrode plate comprises a control electrode, a dielectric layer and a second hydrophobic layer; at least one hydrophilic point is etched on the first hydrophobic layer of the upper electrode plate.

[0017] Preferably, the control electrode comprises at least two liquid reservoir electrode units, each of which is connected to a channel electrode, and the intersection of each channel electrode is a membrane preparation area, and the membrane preparation area is opposite to the hydrophilic point.

[0018] Preferably, the liquid reservoir electrode unit comprises at least a first liquid reservoir electrode unit and a second liquid reservoir electrode unit for carrying oppositely charged film-forming liquid droplets and a cleaning liquid reservoir electrode unit.

[0019] Preferably, the control electrode comprises a waste liquid collecting electrode unit, and the waste liquid collecting electrode unit is connected to the membrane preparation area via a channel electrode.

[0020] Preferably, a plurality of hydrophilic points are provided on the upper electrode plate to form a hydrophilic point array.

[0021] The present invention combines the preparation of digital microfluidic chip with electrostatic self-assembled film, makes hydrophilic points on the chip plate, and transports the film-forming droplets to the hydrophilic points in sequence. Under the action of electrostatics, adjacent polycationic electrolyte layers and polyanionic electrolyte layers (or colloidal nanoparticles, etc.) are deposited alternately, and self-assembled films of specific thickness, number of layers and composition are automatically grown layer by layer at the hydrophilic points. It has the following beneficial effects:

[0022] 1) Extremely fast preparation of electrostatic self-assembled films: The present invention proposes a method for preparing electrostatic self-assembled films based on digital microfluidic chips. Due to the small volume of digital microfluidic droplets, fast mass transfer speed, and fast molecular layer deposition speed, compared with the traditional self-assembled film preparation method, the preparation of electrostatic self-assembled films by the present invention greatly shortens the time and greatly improves the synthesis efficiency of electrostatic self-assembled films. In the experiments conducted, the synthesis time of a single bilayer self-assembly based on a digital microfluidic chip was shortened to 2 minutes, saving 81% of the time;

[0023] 2) Fully automatic control, reducing the consumption of manpower and reagents: The digital microfluidic chip can transport the film-forming droplets to the hydrophilic point for deposition according to the pre-set path through the peripheral control circuit and control software. The whole process does not require human operation, and can realize the preparation of fully automatic electrostatic self-assembled films. At the same time, the droplet volume is very small, which reduces the consumption of reagents;

[0024] 3) High-throughput parallel synthesis of multiple electrostatic self-assembled membranes: hydrophilic spots can be made into large-scale arrays. For example, on a digital microfluidic chip with 1000×1000 drive units, a 100×100 hydrophilic spot array can be made, which can be used for high-throughput parallel synthesis of electrostatic self-assembled membranes with different numbers of layers, different components and different arrangement orders.

[0025] 4) Screening of the synthesis conditions of electrostatic self-assembled films: The synthesis of electrostatic self-assembled films is affected by conditions such as pH value, temperature, salt concentration, solution concentration, deposition time, and substrate surface properties. Droplets with different salt concentrations, solution concentrations, and pH values ​​can be prepared on the digital microfluidic chip. At the same time, a micro-heating system can be integrated, and different chemical modification layers can be made at the hydrophilic points of the upper electrode to achieve the screening of different electrostatic self-assembled film conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the digital microfluidic chip according to Example 1 of the present invention.

[0027] Figure 2 It is a schematic diagram of the control electrode structure of the digital microfluidic chip in Example 1 of the present invention.

[0028] Figure 3(a) and Figure 3(b) are the surface morphology micrographs of 10-layer and 20-layer PDDA / PSS electrostatic self-assembled films, respectively.

[0029] Figure 4 It is a comparison chart of the synthesis time of PDDA / PSS electrostatic self-assembled films with different numbers of layers in the traditional method and Example 1.

[0030] Figure 5 This is a graph of the thickness of the PDDA / PSS electrostatic self-assembled film corresponding to different numbers of bilayers in Example 1.

[0031] Figure 6 It is a schematic diagram of the structure of the digital microfluidic chip of Example 2.

[0032] Figure 7 It is a schematic diagram of the structure of the digital microfluidic chip of Example 3. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific manner, and therefore cannot be understood as limiting the present invention. The terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0034] Example 1

[0035] A method for preparing an electrostatic self-assembled film comprises the following steps:

[0036] 1) Reagent preparation. Various film-forming droplets are loaded in the corresponding liquid reservoir electrode units of the digital microfluidic chip, silicone oil is used to wrap each film-forming droplet, deionized water is loaded in the washing liquid reservoir electrode unit, and each liquid reservoir electrode unit is pre-energized.

[0037] 2) Preparation and accumulation of the 1st to Nth molecular layer membranes, where N ≥ 2 and is an integer: prepare each molecular layer membrane layer by layer, and accumulate layer by layer at the hydrophilic point to form an electrostatic self-assembled membrane. The electrostatic self-assembled membrane is composed of a number of molecular layer membranes accumulated layer by layer, which can be a bilayer (an electrostatic self-assembled membrane formed by alternating deposition of two film-forming material molecular layers with opposite charges), or three or more different film-forming materials accumulated layer by layer to achieve arbitrary adjustment of the components in the membrane. The preparation of each molecular layer membrane includes the following steps:

[0038] 21) Preparation of the first monolayer, dispensing the first reagent droplet from the first liquid reservoir electrode unit, specifically, the reagent droplet can be dispensed from the target liquid reservoir electrode unit by sequentially turning on and off the electrodes adjacent to the target liquid reservoir electrode unit through the peripheral electronic control circuit and control software. In this step, the target liquid reservoir electrode unit is the first liquid reservoir electrode unit, and after dispensing the reagent droplet, it is transported to the hydrophilic point through the channel electrode. The droplet driving device and method can be implemented by the technology recorded in patents such as ZL201711171133.5 and ZL202122866108.7, or other related technologies, which are all prior art and will not be described here.

[0039] After standing for more than 5 seconds, the charged substances are adsorbed to the hydrophilic points under the electrostatic effect of the membrane layer itself, and the droplets are moved away from the hydrophilic position to the waste liquid collection electrode unit by the electrowetting force. Specifically, the waste liquid can be transferred to the waste liquid collection electrode unit by energizing the target electrode, which is the waste liquid collection electrode unit in this case. Then, the cleaning droplets are distributed from the cleaning liquid reservoir electrode unit and transported to the hydrophilic points through the channel electrode to wash away the residual reagents at the hydrophilic points. Similarly, the cleaned waste liquid is transferred to the waste liquid collection electrode unit, and only the single layer with strong electrostatic attraction remains on the electrode plate.

[0040] 22) Preparation of the Nth monolayer membrane, dispensing the Nth reagent droplet from the Nth liquid reservoir electrode unit, transporting the droplet to the hydrophilic site through the channel electrode connected thereto, standing for more than 5 seconds, the Nth reagent droplet and the N-1th reagent droplet carry opposite charges, so that the polymer or particles with opposite charges in the Nth reagent droplet are deposited on the surface of the N-1th molecular layer under the action of electrostatic force; using electrowetting force to move the droplet away from the hydrophilic site to the waste liquid collection electrode unit; after deposition, transporting the cleaning droplet to the hydrophilic site through the channel electrode, and washing away the residual reagent with the cleaning droplet. The waste liquid is transferred to the waste liquid collection electrode unit through the channel electrode.

[0041] The predetermined number of layers is finally reached by the accumulation of each molecular layer on the hydrophilic point, thus completing the preparation of the electrostatic self-assembled film.

[0042] Because the area of ​​the hydrophilic points is small, the electrostatic self-assembled film synthesized by the digital microfluidic chip has high uniformity, and as the number of single-layer films increases, the flatness and density of the film layer will gradually increase.

[0043] The film-forming droplets in the present invention can be selected from one or more of polycationic or anionic electrolytes, inorganic small particles, metal colloidal particles, and biomacromolecules. The polycationic or anionic electrolyte can be polyaniline (PANI), nitrogen-containing polyelectrolyte polyacrylonitrile (PN-CAN), diazo resin (NDR), polydiallyldimethylammonium chloride (PDDA), polystyrene sulfonic acid (PSS), spiroxazine dyes, polyvinyl alcohol (PVA), polyvinyl sulfate (PVS), polypropylene (PP), poly(allylamine·hydrochloric acid) (PAH), etc.; the inorganic small particles are charged II-VI group semiconductor material nanoparticles synthesized from any one or more of SiO2, TiO2, CdTe, CdS, and ZnS.

[0044] The present invention uses electrowetting force to transport film-forming material droplets to hydrophilic sites, and automatically grows a composite film with a specific thickness, number of layers and composition layer by layer on the hydrophilic sites of a digital microfluidic chip through electrostatic interaction.

[0045] The present invention also provides a digital microfluidic chip for preparing the above-mentioned electrostatic self-assembled film, such as Figure 1 As shown, it includes an upper plate 1 and a lower plate 2, the upper plate 1 includes a ground electrode 11 and a first hydrophobic layer 12; the lower plate 2 includes a control electrode 21, a dielectric layer 22 and a second hydrophobic layer 23; at least one hydrophilic point 13 is etched on the first hydrophobic layer 12 of the upper plate 1, and the etching can be performed by laser ablation or dry etching.

[0046] In the present invention, the upper plate is a ground electrode coated with a hydrophobic material. Wherein, the ground electrode can be a conductive material such as gold, silver, chromium, copper, aluminum, ITO, and the deposition method can be magnetron sputtering, electron beam thermal evaporation, etc. The hydrophobic material can be perfluoro (1-butyl vinyl ether) polymer CYTOP, polytetrafluoroethylene PTFE, fluorinated ethylene propylene copolymer FEP, ethylene-trifluorochloroethylene copolymer ECTE, polyfluoroethylene ETFE, perfluoroalkyl compound PFA, Teflon Teflon, polyolefin, polyamide, polyacrylonitrile, molten paraffin, polydimethylsiloxane PDMS, alkoxysilane hybrid material, fluorinated polyethylene, etc. The production of the hydrophilic pattern of the hydrophobic layer adopts general local stripping technology (such as dry etching, laser ablation, etc.), and the shape can be circular, square, half-moon, etc.

[0047] The lower plate is a control electrode covered with a dielectric layer and a hydrophobic layer. The electrode material can be gold, silver, chromium, copper, aluminum, ITO, etc. The dielectric material can be parylene, alumina, silicon nitride, polyamide, polyethylene, polytetrafluoroethylene, or a composite film thereof. The hydrophobic material can be the same as the upper plate material.

[0048] like Figure 2As shown, the control electrode 21 includes at least two liquid reservoir electrode units 3 , each of which is connected to a channel electrode 4 , and the intersection of each channel electrode 4 is a membrane preparation area 41 , which is opposite to the hydrophilic point 13 .

[0049] The liquid reservoir electrode unit 3 includes at least two first liquid reservoir electrode units 31 and second liquid reservoir electrode units 32 for carrying oppositely charged film-forming droplets and a cleaning liquid reservoir electrode unit 33. Of course, a third and fourth liquid reservoir electrode units can also be provided as required. The control electrode 21 includes a waste liquid collection electrode unit 34, which is connected to the membrane preparation area 41 through a channel electrode 4.

[0050] The above example is a single synthesis site of an electrostatic self-assembled film on a digital microfluidic chip. In other embodiments, a plurality of hydrophilic points 13 may be provided on the upper electrode plate 1 to form a hydrophilic point array. Then, a plurality of electrostatic self-assembled films of the same type may be synthesized at the same time, which will greatly improve the synthesis efficiency of the film layer and realize the high-throughput automated synthesis of the electrostatic self-assembled film.

[0051] Normally, since the area of ​​each hydrophilic point is very small (less than 1mm×1mm), hundreds or thousands of hydrophilic point arrays can be integrated on a certain upper plate area, and each hydrophilic point in the array can quickly perform a uniform synthesis of a droplet of electrostatic self-assembled film. In a large-scale array, each hydrophilic point can prepare the same electrostatic self-assembled film, realizing the preparation of a certain amount of electrostatic self-assembled film.

[0052] In large-scale hydrophilic point arrays, different types of electrostatic self-assembled composite films can also be prepared to achieve high-throughput thin film synthesis; or for the same film-forming material, different synthesis conditions can be used, such as changing different pH values, concentrations, deposition times, external electric fields and other factors to achieve the screening of the optimal conditions for electrostatic self-assembled thin film synthesis.

[0053] Specifically in this embodiment, the digital microfluidic chip and the preparation method of the electrostatic self-assembled film are used to prepare a bilayer electrostatic self-assembled film using two film-forming materials, PDDA and PSS, that is, the molecular layers separated from each other use the same reagent droplets. Specifically, during operation, the preparation method of the electrostatic self-assembled film is used to cross-film the two reagent droplets of PDDA and PSS layer by layer until the predetermined number of layers is reached.

[0054] As shown in Figures 3(a) and 3(b), Figures 3(a) and 3(b) correspond to the surface morphologies of self-assembled films with 10 and 20 monolayers, respectively. In this embodiment, a monolayer refers to a bilayer, i.e., a film synthesized from a layer of PDDA and PSS. By comparing Figures 3(a) and 3(b), it is found that the 10-layer (PDDA / PSS) electrostatic self-assembled film has a relatively rough surface structure. As the number of bilayers increases, the surface of the 20-layer (PDDA / PSS) electrostatic self-assembled film is relatively flat and smooth. The electrostatic self-assembled film synthesized by the digital microfluidic chip has a high uniformity, and as the number of layers increases, the flatness and density of the film layer will gradually increase. A larger number of bilayers will make the rough surface morphology of the defective substrate become relatively smooth and dense.

[0055] At the same time, the applicant has counted the synthesis time. Due to the small volume of droplets in the digital microfluidic chip and the very fast mass transfer rate, the synthesis time of the electrostatic self-assembled membrane is greatly reduced. Taking the PDDA / PSS electrostatic self-assembled membrane as an example, compared with the traditional layer-by-layer electrostatic self-assembly process, the self-assembly process time on the digital microfluidic platform of the present invention is greatly reduced. Figure 4 The time required for the traditional electrostatic self-assembly process to synthesize the electrostatic self-assembly film of different numbers of PDDA / PSS bilayers by using the electrostatic self-assembly film of the present invention is: Figure 4 It can be found that on the digital droplet microfluidic platform, that is, using the present invention, the average time required for the automated self-assembly of a single bilayer membrane is only 2 minutes, which is 18.87% of the time required by the traditional process, saving 81.13% of the time.

[0056] The applicant also tested the PDDA / PSS bilayer electrostatic self-assembled film. The test results are as follows: Figure 5 As shown, when the bilayer film has 10 layers, the thickness of the self-assembled film is 20nm. When the bilayer film has 15 layers, the thickness of the self-assembled film is 31nm. Continuing to increase the number of layers to 20, the thickness of the self-assembled film is 43nm. It can be found from the figure that the thickness substantially presents a linear growth with the increase of the number of layers, indicating that the electrostatic self-assembled film prepared by the method of the present invention and the chip has a good assembly effect and a stable film forming process. Therefore, after thousands of cycles of alternating deposition, a bilayer film with thousands or tens of thousands of layers can be synthesized, that is, the synthesis of a micron-level or even millimeter-level thick film of electrostatic self-assembly is realized.

[0057] Example 2

[0058] The preparation method of the electrostatic self-assembled film and the digital microfluidic chip used in Example 2 are basically the same as those in Example 1, except that Example 2 uses three different film-forming materials A, B, and C, and the film-forming materials A, B, and C have two opposite charges. The specific film-forming materials A, B, and C can be selected from the above-mentioned film-forming materials. The only difference from Example 1 is that there are three film-forming materials, and it is sufficient to ensure that two adjacent molecular layers have opposite charges. At the same time, there are at least three liquid reservoir electrode units in order to load three different reagent droplets A, B, and C. Figure 6 As shown, the three different film-forming droplets all move toward the hydrophilic point, i.e., the electrostatic self-assembled film preparation area, under the action of the electrowetting force, and eventually accumulate layer by layer to form a film.

[0059] Example 3

[0060] like Figure 7 As shown, the difference between Example 3 and Example 1 is that a hydrophilic point array structure is prepared on the upper plate of the digital microfluidic chip. Each hydrophilic point can self-assemble a thin film, and the array hydrophilic point can realize the parallel synthesis of multiple thin films. The size of the hydrophilic point is between 10 microns and 1 mm. On a digital microfluidic chip controlled by a 100×100 to 1000×1000 array thin film transistor, 1000-100,000 hydrophilic points can be made, so 1000-100,000 electrostatic self-assembled films of the same type can be synthesized at the same time, which will greatly improve the synthesis efficiency of the film layer and realize the high-throughput automated synthesis of electrostatic self-assembled films.

[0061] Other Implementations

[0062] When the present invention is implemented, the array hydrophilic points on the digital microfluidic chip can be used for the simultaneous synthesis of multiple electrostatic self-assembled films. For example, on a digital microfluidic platform controlled by a 1000×1000 thin film transistor switch array, 100,000 hydrophilic point arrays can be made, and more than 600 kinds of film-forming material droplets can be stored. Each droplet is deposited at the hydrophilic point at the same time through large-scale arbitrary arrangement and combination, and multiple electrostatic self-assembled films with different orders, different components, and different numbers of layers can be prepared.

[0063] By adopting the present invention, the preparation method of the electrostatic self-assembled film based on the digital microfluidic chip can be used to screen the synthesis conditions of various electrostatic self-assembled films. For example, the synthesis of the electrostatic self-assembled film is affected by the following factors: 1. Temperature. High temperature can accelerate the assembly rate of the film, but it may also lead to an unstable film structure. The desired film properties can be obtained at an appropriate temperature. 2. pH value. Different film-forming materials have different charge states under different pH conditions, and the charge state affects the strength and direction of the electrostatic interaction. By adjusting the pH value of the solution, the assembly rate and structure can be controlled. 3. Salt concentration. At a higher salt concentration, ions will compete with the molecules on the surface to interact, thereby reducing the stability of the self-assembled film. Therefore, when preparing the electrostatic self-assembled film, it is usually necessary to control the salt concentration to achieve the ideal film structure and performance. 4. Solution concentration and deposition time. Higher solution concentration and long deposition time usually lead to the formation of a thicker film layer. 5. Substrate surface properties. Different surface properties can guide the adsorption and arrangement of self-assembled molecules, thereby affecting the structure and performance of the film. On the digital microfluidic chip, the droplets undergo a large amount of mixing and splitting, and can have different concentrations of membrane solutions, salt solutions or different pH values, and then be deposited at hydrophilic points, which can screen out the optimal conditions for electrostatic self-assembled films.

[0064] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing an electrostatic self-assembled film, characterized in that: The following steps are involved: 1) Reagent preparation: various film-forming droplets are loaded in the corresponding liquid reservoir electrode units of the digital microfluidic chip, silicone oil is used to wrap each of the film-forming droplets, deionized water is loaded in the cleaning liquid reservoir electrode unit, and each of the liquid reservoir electrode units is pre-energized; 2) Preparation and accumulation of the 1st to Nth molecular layer films, wherein N ≥ 2 and is an integer: each molecular layer film is prepared layer by layer and accumulated layer by layer at the hydrophilic point to form an electrostatic self-assembled film, and the preparation of each molecular layer film includes the following steps: 21) Preparation of the first molecular layer membrane, dispensing a first reagent droplet from the first liquid reservoir electrode unit, and transporting it to the hydrophilic point through the channel electrode, standing for more than 5 seconds, the charged substance is adsorbed to the hydrophilic site, and the droplet is moved away from the hydrophilic position by the electrowetting force to the waste liquid collection electrode unit; dispensing a cleaning liquid droplet from the cleaning liquid reservoir electrode unit, transporting it to the hydrophilic point through the channel electrode, washing away the residual reagent at the hydrophilic point, and ensuring that only a single layer with strong electrostatic attraction remains on the electrode plate; 22) Preparation of the Nth molecular layer membrane, dispensing the Nth reagent droplet from the Nth liquid reservoir electrode unit, transporting the droplet to the hydrophilic site through the channel electrode connected thereto, and standing for more than 5 seconds, the Nth reagent droplet and the N-1th reagent droplet have opposite charges, so that the oppositely charged polymers or particles in the Nth reagent droplet are deposited on the surface of the N-1th molecular layer under the action of electrostatic force; using electrowetting force to move the droplet away from the hydrophilic position to the waste liquid collection electrode unit; after the deposition is completed, transporting cleaning droplets to the hydrophilic point through the channel electrode, and washing away the residual reagent with the cleaning droplets.

2. The method for preparing an electrostatic self-assembled film according to claim 1, wherein: In step 2), the separated molecular layers are treated with droplets of the same reagent.

3. The method for preparing an electrostatic self-assembled film according to claim 1, wherein: In the step 2), the reagent droplets are dispensed from the target liquid reservoir electrode unit by sequentially turning on and off the electrodes adjacent to the target liquid reservoir electrode unit.

4. The method for preparing an electrostatic self-assembled film according to claim 1, wherein: The film-forming droplets are selected from one or more of polycationic or anionic electrolytes, inorganic small particles, metal colloidal particles, and biological macromolecules.

5. The method for preparing an electrostatic self-assembled film according to claim 4, wherein: The polycationic or anionic electrolyte can be polyaniline, nitrogen-containing polyelectrolyte polyacrylonitrile, diazo resin, polydiallyldimethylammonium chloride, sodium polystyrene sulfonate, spirooxazine dye, polyvinyl alcohol, polyvinyl sulfate, polypropylene, polyallylamine hydrochloride; the inorganic small particles are charged II-VI semiconductor material nanoparticles synthesized from any one or more of SiO2, TiO2 or CdTe, CdS, and ZnS.

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