A magnetic PDMS elastic structure and a micro-droplet dispenser based on magnetic force control

Abstract

The present invention provides a magnetic PDMS elastic structure and a micro-droplet dispenser based on magnetic force control, which includes a liquid separation tube, a liquid-carrying surface, a magnetic PDMS elastic plate, a magnet, and a plurality of liquid channels. The liquid separation tube is arranged above the liquid-carrying surface, and a plurality of the liquid channels are distributed around the liquid-carrying surface. A magnetic PDMS elastic plate is provided between each liquid channel and the liquid-carrying surface, and a magnet is provided below the liquid channel. The present invention performs micro-droplet separation based on the magnetic PDMS elastic structure, which can achieve high-precision and high-speed micro-droplet separation, can achieve precision control at the micron level, and can achieve precise separation and positioning of droplets at the micron scale. It can achieve rapid liquid separation, reduce the time of experimental operation, and improve the experimental efficiency. It can achieve highly stable droplet separation, avoid droplet aggregation and fluctuation, and improve the repeatability and accuracy of the experiment.

Description

Technical Field

[0001] The present invention relates to the technical field of microfluidics, and in particular to a magnetic PDMS elastic structure and a micro-droplet dispenser based on magnetic force control. Background Art

[0002] Microfluidic technology is a technology that uses micro-scale channels and microfluidic manipulation techniques to perform operations on tiny liquids, and has advantages such as high efficiency, high throughput, and low cost. The micro-droplet dispenser is developed on the basis of microfluidic technology, and its main feature is the ability to separate a mixed liquid into several different liquids, with high precision and controllability. Micro-droplet dispensers are widely used in the fields of biomedicine, chemistry, environmental monitoring, etc. In the field of biomedicine, micro-droplet dispenser technology has been used in high-throughput drug screening, single-cell analysis, etc., and has very broad application prospects.

[0003] The micro-droplet dispenser is an excellent microfluidic technology, but it also has some deficiencies, mainly including the following aspects: high equipment cost: the micro-droplet dispenser needs to use multiple technologies such as micro-nano processing, optical imaging, and high-precision control, so its equipment cost is relatively high and it is not suitable for large-scale applications; difficult operation: the micro-droplet dispenser needs to perform droplet operations at the micron level, with high technical requirements for the operator, and certain professional knowledge and experience are required; unstable droplets: the droplets generated in the micro-droplet dispenser are often very small, with a certain surface tension, and are prone to problems such as aggregation and fusion, affecting the stability of the droplets; long operation time: since the operation of the micro-droplet dispenser requires multiple liquid separations, and each liquid separation takes a certain amount of time, its operation time is relatively long. Therefore, there is an urgent need for a micro-droplet dispenser with low cost, simple operation, safety and reliability. Summary of the Invention

[0004] The purpose of the present invention is to provide a magnetic PDMS elastic structure and a micro-droplet dispenser based on magnetic force control. Micro-droplet separation based on the magnetic PDMS elastic structure can achieve high-precision and high-speed micro-droplet separation.

[0005] According to one purpose of the present invention, the present invention provides a magnetic PDMS elastic structure, which is made by the following method and includes the following steps:

[0006] Step 1: Process rectangular holes on a silicon substrate, and after washing, obtain a micro-structure mold;

[0007] Step 2: Pour magnetic neodymium iron boron particles above the micro-structure mold, place a neodymium iron boron permanent magnet under the micro-structure mold, and move it back and forth several times in the area around the rectangular hole to pull the magnetic neodymium iron boron particles placed on the top surface of the micro-structure mold into the rectangular hole;

[0008] Step 3: Inspect the microstructure mold under an optical microscope to ensure that the rectangular holes are fully filled with magnetic neodymium iron boron particles, and then wipe the top with a cotton cloth dipped in alcohol to remove the excess magnetic neodymium iron boron particles on the top;

[0009] Step 4: Mix the polydimethylsiloxane (PDMS) matrix and the curing agent in a mass ratio of 10:1, stir evenly, let it stand for defoaming to obtain a PDMS mixture, pour it into the structure with magnetic neodymium iron boron particles filled in the rectangular holes in Step 3, cure it at room temperature, and carefully peel off the mold after the PDMS mixture is completely cured to obtain a magnetic PDMS elastic structure;

[0010] Step 5: Modify the wettability of the surface of the magnetic PDMS elastic structure to obtain superhydrophobic performance on the surface, and the production is completed.

[0011] Further, in Step 1, the silicon substrate has a thickness of 5 mm.

[0012] Further, in Step 1, the silicon substrate after processing the rectangular holes is cleaned with deionized water and absolute ethanol.

[0013] Further, in Step 2, before pouring the magnetic neodymium iron boron particles above the microstructure mold, a layer of poly-p-xylene with a thickness of 0.5 - 1 μm is coated on the microstructure mold.

[0014] Further, in Step 4, the curing time of the PDMS mixture is 24 - 48 hours.

[0015] Further, in Step 5, the magnetic PDMS elastic structure is sprayed with a superhydrophobic spray containing silicon dioxide nanoparticles to obtain superhydrophobic performance on the surface.

[0016] According to another object of the present invention, the present invention provides a micro-droplet dispenser based on magnetic force control, including a liquid separation tube, a liquid-carrying surface, a magnetic PDMS elastic plate, a magnet, and a plurality of liquid channels. The liquid separation tube is arranged above the liquid-carrying surface, a plurality of the liquid channels are distributed around the liquid-carrying surface, the magnetic PDMS elastic plate is arranged between each liquid channel and the liquid-carrying surface, and the magnet is arranged below the liquid channel.

[0017] Further, the number of the liquid channels is five.

[0018] Further, the bottom of the wall of the liquid channel is a hydrophobic bottom, and the liquid-carrying surface is treated by hydrophobic treatment.

[0019] Further, the bottom of the wall of the liquid channel is covered with a superhydrophobic filter paper.

[0020] The technical solution of the present invention is based on a magnetic PDMS elastic structure for micro-droplet liquid separation, which can achieve high-precision and high-speed micro-droplet separation, can achieve precision control at the micron level, and can achieve precise separation and positioning of droplets at the micron scale. It can achieve rapid liquid separation, reduce the time of experimental operations, and improve experimental efficiency. It can achieve highly stable droplet separation, avoid droplet aggregation and fluctuations, and improve the repeatability and accuracy of experiments. Description of the Drawings

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 Schematic diagram of the manufacturing steps of the magnetic PDMS elastic structure body in the embodiment of the present invention;

[0023] Figure 2 Schematic diagram of the deflection mechanism of the magnetic PDMS elastic structure body in the embodiment of the present invention under a magnetic field.

[0024] Figure 3 Schematic diagram of the structure of the micro-droplet dispenser in the embodiment of the present invention.

[0025] In the figure: 1, silicon substrate; 2, micro-structure mold; 3, magnetic neodymium iron boron particles; 4, neodymium iron boron permanent magnet; 5, PDMS mixture; 6, magnetic PDMS elastic structure; 7, liquid channel; 8, liquid separation tube; 9, liquid-carrying surface; 10, magnet; 11, magnetic PDMS elastic plate. Specific Embodiments

[0026] The following will clearly and completely describe the technical solutions of the present invention in combination with the embodiments. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0028] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined. In addition, the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Embodiment 1

[0030] As Figure 1 - Figure 2 shown,

[0031] A magnetic PDMS elastic structure is made by the following method, including the following steps:

[0032] Step 1: Using lithography technology, a rectangular hole structure with a large aspect ratio is processed on a silicon substrate 1 (about 5 mm thick). After washing with deionized water and anhydrous ethanol, a micro-structured mold 2 is obtained.

[0033] Step 2: A layer of parylene with a thickness of 0.5 - 1 um is coated on the obtained micro-structured mold 2. Then, magnetic neodymium iron boron particles 3 (particle size 1 - 10 um) are poured above the micro-structured mold 2. In order to achieve uniform and sufficient filling of the magnetic neodymium iron boron particles 3 in the rectangular holes, a small neodymium iron boron permanent magnet 4 is placed on the lower side of the micro-structured mold 2 and moved back and forth several times in the area around the rectangular holes, so as to effectively pull the magnetic neodymium iron boron particles 3 placed on the top surface of the micro-structured mold 2 into the rectangular holes.

[0034] Step 3: Examine the microstructure mold 2 under an optical microscope to ensure that the rectangular holes are fully filled with magnetic neodymium iron boron particles 3. Then, wipe the top with a cotton cloth dipped in alcohol to remove the excess magnetic neodymium iron boron particles 3 on the top.

[0035] Step 4: Mix the polydimethylsiloxane (PDMS) matrix and the curing agent in a mass ratio of 10:1 and stir evenly. After standing for defoaming, obtain the PDMS mixture 5. Pour it into the structure with magnetic neodymium iron boron particles filled in the rectangular holes in Step 3, and cure it at room temperature. Increase the curing time (24 - 48 hours). After the PDMS mixture 5 is completely cured, carefully peel off the mold to obtain the magnetic PDMS elastic structure 6.

[0036] Step 5: Modify the wettability of the surface of the magnetic PDMS elastic structure 6. Spray the magnetic PDMS elastic structure 6 with a superhydrophobic spray containing silica nanoparticles to obtain superhydrophobic properties on the surface, and the production is completed.

[0037] In this embodiment, a 0.5 - 1 μm thick parylene layer is coated on the prepared microstructure mold 2 to facilitate demolding and prevent the PDMS mixture 5 from adhering to or contacting the microstructure mold 2, which may cause difficulty in curing the PDMS mixture and thus difficult demolding.

[0038] In Step 4, a low curing temperature at room temperature is used to reduce the shrinkage of the PDMS mixture, prevent the expansion of tiny air bubbles in the PDMS mixture, and effectively inhibit the formation of cavity air bubbles in the rectangular hole structure. The long curing time (24 - 48 hours) provides more time for the diffusion of neodymium iron boron magnetic particles in the PDMS mixture medium, enabling the PDMS to completely surround the magnetic particles, thus forming a uniform structure.

[0039] The action mechanism of the microstructure prepared in this embodiment under a magnetic field is as Figure 2 shown:

[0040] When a permanent magnet approaches the magnetic PDMS elastic structure 6, since the magnetic PDMS elastic structure 6 contains magnetic materials (neodymium iron boron particles), under the action of the magnetic field, the magnetic PDMS elastic structure 6 deflects towards the magnet. The closer the magnet is to the structure, the greater the magnetic force exerted on the structure, and the larger the deflection angle of the rectangular plate.

[0041] As Figure 3 shown, a micro-droplet dispenser based on magnetic force control includes a liquid separation tube 8, a liquid-carrying surface 9, a magnetic PDMS elastic plate 11, a magnet 10, and a plurality of liquid channels 7. The liquid separation tube 8 is arranged above the liquid-carrying surface 9. A plurality of liquid channels 7 are distributed around the liquid-carrying surface 9. A magnetic PDMS elastic plate 11 is provided between each liquid channel 7 and the liquid-carrying surface 9, and a magnet 10 is provided below the liquid channel 7.

[0042] The liquid separation mechanism of a micro-droplet dispenser based on magnetic control is as follows:

[0043] As shown Figure 3 in the attached figure, there are five liquid channels 7 on the surface 9 of the carrier liquid. More liquid channels can be constructed according to requirements. The bottom of the wall of each liquid channel 7 is hydrophobic. Specifically, the bottom of the wall of each liquid channel 7 can be covered with super-hydrophobic filter paper.

[0044] The liquid to be separated is stored in the liquid separation tube 8. The liquid stored in the liquid separation tube 8 is injected onto the surface 9 of the liquid carrier of the liquid separation device in a specific order. The surface 9 of the liquid carrier is treated by hydrophobic treatment. By controlling the movement direction of the control magnet 10 below each liquid channel 7, the magnetic PDMS elastic plate 11 bends under the action of the magnetic field. The liquid is directionally transported to the corresponding liquid channel 7 through the liquid channel under the action of gravity and surface force, thereby showing that the liquid separation system can perform real-time, controllable and unidirectional water transportation of the liquid in a specific direction.

[0045] The micro-droplet dispenser based on magnetic control of the present invention can perform micro-droplet separation based on a magnetic PDMS elastic structure, and can achieve high-precision and high-speed micro-droplet separation, and has the following advantages:

[0046] High precision: It can achieve precision control at the micron level, and can achieve precise separation and positioning of droplets at the micron scale.

[0047] High speed: It can achieve rapid liquid separation, reduce the time of experimental operation, and improve the experimental efficiency.

[0048] High stability: The micro-droplet dispenser can achieve high-stability droplet separation, avoid droplet aggregation and fluctuation, and improve the repeatability and accuracy of the experiment.

[0049] No contact: The micro-droplet dispenser can achieve droplet separation without contact, avoid contamination and damage to the sample, and ensure the reliability and accuracy of the experiment.

[0050] Low consumption: The preparation method of the structure of the micro-droplet dispenser has a simple process. It only requires simple preparation steps, relatively inexpensive equipment, and relatively environmentally friendly materials to complete the preparation, avoiding high-cost equipment, templates, and consumables. By controlling liquid separation with magnetic force, it shows the instantaneous response ability and remote control ability of magnetic drive conversion, without external energy, and has safety and low-consumption reliability. The micro-droplet dispenser based on magnetic control of the present invention can be widely applied to fields such as biomedicine, chemical analysis, and environmental monitoring, and has important scientific research and practical application values.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A micro-droplet dispenser based on magnetic control, characterized in that, It includes a liquid separation tube, a liquid-carrying surface, a magnetic PDMS elastic plate, a magnet and a plurality of liquid channels. The liquid separation tube is arranged above the liquid-carrying surface. A plurality of the liquid channels are distributed around the liquid-carrying surface. The magnetic PDMS elastic plate is arranged between each liquid channel and the liquid-carrying surface. The magnet is arranged below the liquid channel; The liquid to be separated is stored in the liquid separation tube. The liquid-carrying surface is treated by hydrophobic treatment. By controlling the movement direction of the magnet below each liquid channel, the magnetic PDMS elastic plate is bent under the action of the magnetic field, and the liquid is directionally transported to the corresponding liquid channel under the action of gravity and surface force; The magnetic PDMS elastic plate is made by the following method, which includes the following steps: Step 1: Process rectangular holes on a silicon substrate, and obtain a micro-structure mold after washing; Step 2: Pour magnetic neodymium iron boron particles above the micro-structure mold, place a neodymium iron boron permanent magnet on the lower side of the micro-structure mold, and move it back and forth several times in the area around the rectangular hole to pull the magnetic neodymium iron boron particles placed on the top surface of the micro-structure mold into the rectangular hole; Step 3: Check the micro-structure mold under an optical microscope to ensure that the rectangular holes are all filled with magnetic neodymium iron boron particles, and then wipe the top with a cotton cloth dipped in alcohol to remove the excess magnetic neodymium iron boron particles on the top; Step 4: Mix and stir the polydimethylsiloxane (PDMS) matrix and the curing agent in a mass ratio of 10:1, let it stand for defoaming to obtain a PDMS mixture, pour it into the structure with magnetic neodymium iron boron particles filled in the rectangular holes in Step 3, cure it at room temperature, and carefully peel and demold it after the PDMS mixture is completely cured to obtain a magnetic PDMS elastic plate; Step 5: Modify the wettability of the surface of the magnetic PDMS elastic plate to obtain super-hydrophobic performance on the surface, and the production is completed.

2. The micro-droplet dispenser based on magnetic control according to claim 1, characterized in that The number of the liquid channels is five.

3. The magnetic force controlled micro-droplet dispenser according to claim 1, wherein The bottom of the wall of the liquid channel is a hydrophobic bottom, and the liquid-carrying surface is treated by hydrophobic treatment.

4. The micro-droplet dispenser based on magnetic control according to claim 1, characterized in that, The bottom of the wall of the liquid channel is covered with super-hydrophobic filter paper.

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