Microfluid directional transport device and preparation method and application thereof

Abstract

The invention relates to the field of droplet programming transportation, and discloses a microfluid directional transportation device and a preparation method and application thereof, the microfluid directional transportation device comprises a substrate with a groove, a flexible polymer layer with a plurality of movable pieces and a lubricating liquid; the flexible polymer layer and the annular protrusion on the face, provided with the groove, of the substrate are connected to form a bag-shaped structure with a cavity, and the cavity is filled with the lubricating liquid. The flexible polymer layer includes a flexible polymer and magnetic particles distributed in the flexible polymer. Under the action of an external magnetic field, the movable piece in the flexible polymer layer can incline by a certain angle in the direction of a magnetic induction line, lubricating liquid is promoted to flow out, and therefore the lubricating liquid and potential energy difference are provided for liquid drop movement, and liquid drop movement is promoted. The micro-fluid directional transport device can be applied to research in the fields of icing prevention, increase of product purity of micro-droplet reaction, constant-temperature storage, dynamic digital display, purification of water drops in oil-water emulsion, underwater bubble capture, underwater resistance reduction and the like.

Description

Technical Field

[0001] The present invention relates to the field of droplet programmed transportation, and particularly to a microfluidic directional transport device, a preparation method thereof, and an application thereof. Background Art

[0002] Droplet transportation refers to controlling the movement direction and path of droplets on a solid surface through external stimuli or material / structure design. Dynamically programmable regulation of droplet movement has important scientific significance and application value in the fields of droplet transportation, reaction control, environmental monitoring, 3D printing, surface self-cleaning, biomedicine, and flexible electronics. To improve the controllability of droplets, researchers have tried to achieve controllable liquid dynamics by designing material surface energy gradients and constructing hierarchical micro-nano structures.

[0003] Specific micro-nano structure designs can achieve directional transportation, rapid movement, or regulation of droplets. Commonly, by designing various surfaces such as anisotropic structures (such as micro-grooves, nanowire arrays), specific patterns (dot matrices, grids), and hollow concave-convex arrays, directional movement of droplets can be achieved under the action of external or internal driving forces. By optimizing the physical and chemical properties of the material itself, efficient droplet transportation can also be carried out. By making gradient distributions of wettability, charge, droplet adhesion ability, surface energy, chemical composition, etc. on the surface, spontaneous directional movement of droplets can also be achieved.

[0004] Although this static droplet method relying only on structures / materials has a certain ability to control droplet operation. However, a unique structure or gradient material design can only correspond to the manipulation of droplets along a specific path. This means that the surface cannot cope with complex and personalized droplet movement requirements, the design iteration is difficult, and there is a lack of certain flexibility in driving droplets. Therefore, it is necessary to perform dynamic stimulation regulation on droplets.

[0005] However, traditional techniques for dynamically stimulating and regulating droplet behavior usually have problems such as limitations in response speed, low energy input efficiency, poor droplet stability, insufficient regulation accuracy, and high cost. How to achieve fast and precise movement manipulation of droplets along a given path through simplified design remains a key challenge.

[0006] Therefore, the existing technologies still need to be improved and developed. Summary of the Invention

[0007] In view of the above deficiencies of the existing technologies, the purpose of the present invention is to provide a microfluidic directional transport device, a preparation method thereof, and an application thereof, aiming to solve the problems of poor droplet stability and insufficient regulation accuracy of existing microfluidic directional transport devices.

[0008] The technical solution of the present invention is as follows:

[0009] In a first aspect, a microfluidic directional transport device is provided, comprising: a substrate with grooves, a flexible polymer layer with a plurality of movable sheets, and a lubricating fluid;

[0010] The flexible polymer layer and the annular protrusion on the surface of the substrate with grooves are connected to form a bag-like structure with a cavity;

[0011] The lubricating fluid is filled in the cavity;

[0012] The flexible polymer layer comprises a flexible polymer and magnetic particles distributed in the flexible polymer.

[0013] In a preferred technical solution, the surface energy of the lubricating fluid is 15-40 mN / m, and the dielectric constant of the lubricating fluid is lower than 15.

[0014] In a preferred technical solution, the lubricating fluid is selected from one or more of dimethyl silicone oil, polydimethylsiloxane, mineral oil, castor oil, olive oil, and perfluoropolyether.

[0015] In a preferred technical solution, the flexible polymer is selected from one or more of polydimethylsiloxane, polyethylene, polyurethane, and silicone rubber.

[0016] In a preferred technical solution, the material of the magnetic particles is selected from one or more of Fe3O4, CIP, Gd-DTPA, SPIO, Gd2O3, FeCo, FeNi, and Y2O3.

[0017] In a preferred technical solution, the diameter of the magnetic particles is 1-10 μm.

[0018] In a preferred technical solution, the mass ratio of the flexible polymer to the magnetic particles is 1:(1-3).

[0019] In a preferred technical solution, the thickness of the flexible polymer layer is 5-50 microns.

[0020] In a preferred technical solution, the groove depth of the groove is 50-500 microns.

[0021] In a preferred technical solution, the shape of the movable sheet is selected from one or more of oval, rectangular, and triangular.

[0022] In a preferred technical solution, the area of the movable sheet is 1000-10000 square microns; the spacing of the movable sheets is 80-200 microns.

[0023] In a preferred technical solution, the microfluidic directional transport device further comprises a magnetic drive device.

[0024] In a second aspect, a preparation method of the microfluidic directional transport device as described in the first aspect is provided, comprising the steps:

[0025] Provide a substrate with grooves;

[0026] Melt and solidify polycaprolactone in the grooves to obtain a first intermediate;

[0027] Mix magnetic particles and uncured flexible polymer to obtain a mixture;

[0028] Cover the mixture on the side of the first intermediate containing polycaprolactone and cure to form a flexible polymer layer to obtain a second intermediate;

[0029] Cut a number of movable sheets on the flexible polymer layer of the second intermediate to obtain a third intermediate;

[0030] Place the third intermediate in a lubricating fluid and heat it in an externally applied magnetic field environment so that the polycaprolactone in the third intermediate is discharged and the lubricating fluid is poured in to obtain the microfluidic directional transport device.

[0031] In a preferred technical solution, in the step of cutting a number of movable sheets on the flexible polymer layer of the second intermediate, the cutting method is selected from one or more of focused ion beam cutting, femtosecond laser cutting, electron beam cutting, and atomic force microscope nano-cutting.

[0032] In a third aspect, provide an application of the microfluidic directional transport device as described in the first aspect in microchemical reactions and droplet transportation.

[0033] Advantageous effects: The present invention provides a microfluidic directional transport device, its preparation method and application. The microfluidic directional transport device includes: a substrate with grooves, a flexible polymer layer with a number of movable sheets, and a lubricating fluid; the flexible polymer layer and the annular protrusions on the surface of the substrate with grooves are connected to form a bag-like structure with a cavity; the lubricating fluid is filled in the cavity; the flexible polymer layer includes a flexible polymer and magnetic particles distributed in the flexible polymer. Under the action of an external magnetic field, the movable sheets in the flexible polymer layer will tilt upward or downward at a certain angle along the direction of the magnetic induction line, promoting the outflow of the lubricating fluid, thereby providing lubricating fluid and potential energy difference for the movement of droplets and promoting the movement of droplets. When the lubricating fluid contacts the water droplet, it will gradually wrap the surface of the droplet to form a nano-scale thin film closed space, which can isolate external pollution and reduce the energy exchange between the outside and the closed space while, so it can be applied to research in fields such as anti-icing, increasing the product purity of micro-droplet reactions, constant temperature preservation, dynamic digital display, purification of water droplets in oil-water emulsions, underwater bubble capture, and underwater drag reduction. The microfluidic directional transport device of the present invention improves the droplet operation accuracy and expands the application range of samples in multiple fields through a non-contact magnetic stimulation method. Description of the Drawings

[0034] Figure 1 It is a schematic diagram of the microfluidic directional transport device of the present invention.

[0035] Figure 2 It is a schematic diagram of the application direction of the microfluidic directional transport device of the present invention in a dynamic digital display screen.

[0036] Figure 3 It is a schematic diagram of the application direction of the microfluidic directional transport device of the present invention in chemical micro-reactions.

[0037] Figure 4 It is a comparison diagram of the energy released when the microfluidic directional transport device of the present invention is applied to a chemical reaction; wherein, A is a heat dissipation diagram of a droplet without a lubricating fluid, and B is a heat dissipation diagram of a droplet with a lubricating fluid.

[0038] Figure 5 It is a schematic diagram of the ability of the microfluidic directional transport device of the present invention to capture and transport underwater bubbles.

[0039] Figure 6 It is a graph showing the change of the internal lubricating fluid mass loss of the microfluidic directional transport devices of Example 1 and Comparative Example 1 of the present invention over time. Detailed implementation manners

[0040] The present invention provides a microfluidic directional transport device and its preparation method and application. To make the purpose, technical solution and effect of the present invention clearer and more definite, the present invention is further described in detail below.

[0041] An embodiment of the present invention provides a microfluidic directional transport device, including: a substrate with grooves, a flexible polymer layer with a plurality of movable sheets, and a lubricating fluid;

[0042] The flexible polymer layer and the annular protrusions on the surface of the substrate with grooves are connected to form a bag-like structure with a cavity;

[0043] The lubricating fluid is filled in the cavity;

[0044] The flexible polymer layer includes a flexible polymer and magnetic particles distributed in the flexible polymer.

[0045] Specifically, inspired by the adjustable wetting function of the foot pads of the weaver ant, the present invention designs a microfluidic directional transport device. Among them, the flexible polymer layer and the substrate form a bag-like structure similar to the soft foot pads of the weaver ant, and the lubricating fluid is similar to the liquid secreted by the weaver ant; under the drive of an external magnetic field, the behavior of the bag-like structure secreting mucus is similar to the contraction and relaxation actions generated by the foot pad muscles of the weaver ant. When a magnetic driving device is placed under the substrate, the flexible polymer layer is attracted by the magnetic field, squeezes the lubricating fluid downward, and the terrain becomes lower; the movable sheet in the flexible polymer layer tilts upward or downward at a certain angle along the direction of the magnetic induction line, promoting the outflow of the lubricating fluid, thereby providing lubricating fluid and potential energy difference for the movement of the droplet and promoting the movement of the droplet. The schematic diagram of the microfluidic directional transport device is as shown in Figure 1 shown.

[0046] Due to the controllable movement of the movable sheet, the microfluidic directional transport device of the present invention can release the lubricating fluid as needed, and compared with the method of directly pouring the lubricating fluid on the flexible polymer layer, it can minimize the loss ability of the lubricating fluid. This magnetic control method is similar to the movement of muscles and mimics the secretion and muscle control ability of the foot pads of the weaver ant to a great extent.

[0047] In one embodiment, the surface energy of the lubricating fluid is 15 - 40 mN / m, and the dielectric constant of the lubricating fluid is less than 15. Preferably, the lubricating fluid is selected from one or more of dimethyl silicone oil, polydimethylsiloxane, mineral oil, castor oil, olive oil, and perfluoropolyether. Specifically, the lubricating fluid has a low surface energy, can wrap the transported droplet, and form a nano-level liquid film on the surface of the transported droplet, thereby forming a nano-level closed space. While isolating external pollution, this nano-level liquid film can reduce the energy exchange between the outside and the closed space, and can be applied to fields such as anti-icing, increasing the purity of chemical reactants, and constant temperature preservation, and reduce the negative impact on the environment caused by the discharge of harmful gases.

[0048] In one embodiment, the microfluidic directional transport device is used for droplet transportation; preferably, the droplet is a hydrophilic droplet carrier, such as a sodium chloride water droplet, an ethanol aqueous solution, etc.; preferably, the hydrophilic droplet carrier contains a solute, and the solute is a hydrophilic substance; preferably, the hydrophilic droplet carrier is poorly soluble or insoluble in the lubricating fluid, and the solubility of the hydrophilic droplet carrier in the lubricating fluid is <0.1 g / L; preferably, the hydrophilic droplet carrier is a strongly polar molecule with a dielectric constant higher than 30.

[0049] In one embodiment, the flexible polymer is selected from one or more of polydimethylsiloxane, polyethylene, polyurethane, and silicone rubber. Specifically, the flexible polymer layer prepared from the flexible polymer of the above materials has a hydrophobic and lipophilic surface and can be used for the transportation of hydrophilic droplet carriers.

[0050] In one embodiment, the material of the magnetic particles is selected from one or more of iron oxide (Fe3O4), carbonyl iron powder (CIP), gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA), superparamagnetic iron oxide (SPIO), gadolinium sesquioxide (Gd2O3), iron-cobalt alloy (FeCo), iron-nickel alloy (FeNi), yttrium sesquioxide (Y2O3).

[0051] In one embodiment, the diameter of the magnetic particles is 1 to 10 μm.

[0052] In one embodiment, the magnetic particles are surface-treated; the surface treatment methods include: adding surfactants, silane coupling agents, ionic dispersants and other functional materials to avoid particle agglomeration. Preferably, one or more of sodium dodecyl sulfate, heptadecafluorodecyltrimethoxysilane, perfluorooctane sulfonate, polyether-modified silicone oil are added to the magnetic particles for surface treatment.

[0053] In one embodiment, the mass ratio of the flexible polymer to the magnetic particles is 1:(1 - 3). Specifically, the high mass ratio of the flexible polymer to the magnetic particles is the reason for the magnetic compliance of the flexible polymer layer and the core for the movable sheet in the flexible polymer layer to drive the droplet.

[0054] In one embodiment, the thickness of the flexible polymer layer is 5 to 50 microns. Specifically, the flexible polymer layer with a suitable thickness can deform under the action of an external magnetic field, and the movable sheet therein will tilt upward or downward at a certain angle, promoting the outflow of the lubricating fluid, thereby providing the lubricating fluid and potential energy difference for droplet transportation and promoting the movement of the droplet.

[0055] In one embodiment, the surface of the flexible polymer layer away from the substrate is modified with a hydrophobic and lipophilic coating. Specifically, the hydrophobic and lipophilic coating is selected from a fluorocarbon coating or a wax coating, etc. The hydrophobic and lipophilic coating can easily isolate the contact between the droplet and the substrate with the lubricating fluid of low surface energy.

[0056] In one embodiment, the groove depth of the groove is 50 to 500 microns. Specifically, the groove with a suitable groove depth can fill an appropriate amount of lubricating fluid, enabling it to be released as needed when transporting the droplet.

[0057] In one embodiment, the shape of the movable sheet is selected from one or more of oval, rectangular, and triangular. Specifically, when the shape of the movable sheet is oval, the connection part between it and the flexible polymer layer is a quarter arc of the perimeter; when the shape of the movable sheet is rectangular, the connection part between it and the flexible polymer layer is any side of the rectangle; when the shape of the movable sheet is triangular, the connection part between it and the flexible polymer layer is any side of the triangle.

[0058] In one embodiment, the area of the movable sheet is 1000 to 10,000 square micrometers; the spacing between the movable sheets is 80 to 200 micrometers.

[0059] In one embodiment, the microfluidic directional transport device further includes a magnetic driving device. Specifically, by adjusting the distance between the magnetic driving device and the droplet to be transported, the slip velocity of the droplet to be transported can be controlled.

[0060] In one embodiment, the magnetic driving device is a combination of one or more permanent magnets.

[0061] In one embodiment, the permanent magnet is selected from one or more of neodymium iron boron magnets, alnico magnets, samarium cobalt magnets, and ferrite magnets. Specifically, for example, neodymium iron boron strong magnets of models such as N52 and N45, alnico strong magnets of model Alnico 8, samarium cobalt magnets of model Sm2Co17, and ferrite strong magnets of models Y30 and Y35.

[0062] The embodiment of the present invention provides a preparation method of the microfluidic directional transport device as described above, including the steps:

[0063] Providing a substrate with grooves;

[0064] Melting and solidifying polycaprolactone in the grooves to obtain a first intermediate;

[0065] Mixing magnetic particles and uncured flexible polymer to obtain a mixture;

[0066] Covering the mixture on the side of the first intermediate containing polycaprolactone and curing to form a flexible polymer layer to obtain a second intermediate;

[0067] Cutting a plurality of movable sheets on the flexible polymer layer of the second intermediate to obtain a third intermediate;

[0068] Placing the third intermediate in a lubricating fluid and heating it in an external magnetic field environment to discharge the polycaprolactone in the third intermediate and fill it with the lubricating fluid to obtain the microfluidic directional transport device.

[0069] Among them, polycaprolactone is a filler in the preparation process, used to form a cavity between the flexible polymer layer and the substrate with grooves, and can also be replaced with a low melting point substance.

[0070] In one embodiment, in the step of cutting a plurality of movable sheets on the flexible polymer layer of the second intermediate, the cutting method is selected from one or more of focused ion beam cutting, femtosecond laser cutting, electron beam cutting, and atomic force microscope (AFM) nanocutting.

[0071] An embodiment of the present invention provides an application of the above-described microfluidic directional transport device in microchemical reactions and droplet transportation.

[0072] Specifically, the present invention designs a microfluidic directional transport device. This microfluidic directional transport device can achieve rapid and precise movement control of droplets along a given path by utilizing the function of effective switching between in-situ pinning and rapid sliding of droplets on a single surface. Therefore, it can be applied to scenarios such as droplet transportation along a programmed path, a new generation of digital displays, improving the purity of chemical reactants, and underwater bubble capture, transportation, and drag reduction.

[0073] In one embodiment, since the wettability of the microfluidic directional transport device is adjustable and controllable, it can capture underwater bubbles and drive the bubbles in the way of driving droplets, and can be applied to the fields of underwater bubble transportation and underwater drag reduction.

[0074] In one embodiment, when the droplet slips in a way of internal rolling, the microfluidic directional transport device can continuously adjust the contact surface between the droplet and the lubricating liquid and dissolve oily substances, so as to be used for the purification of droplets in an oil-water emulsion.

[0075] The present invention will be further described below through specific embodiments.

[0076] Example 1

[0077] This embodiment provides a microfluidic directional transport device, and its preparation method includes the following steps:

[0078] (1) First, use laser marking to make a groove with a depth of 50 micrometers and a length and width of 2 centimeters on an aluminum plate. Secondly, put solid polycaprolactone into the groove and heat it to dissolve it into a liquid to fill the inside of the groove. Then, soak CIP in a 3% mass fraction solution of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane for 3 hours, and take it out with a magnet. And spread the PDMS fluid mixed with 50% mass of the above CIP on the plane filled with polycaprolactone, and put it in an oven at 60 °C for curing for 5 hours. After curing, the thickness of the PDMS layer containing CIP is about 10 micrometers.

[0079] (2) Use femtosecond laser to cut the above PDMS layer containing CIP to form a plurality of rectangular movable sheets. The length of a single movable sheet is 50 micrometers and the width is 30 micrometers. Keep the side with a length of 30 micrometers connected to the main body. The spacing between the movable sheets is 80 micrometers, and an array is formed between the plurality of movable sheets, covering the entire PDMS layer containing CIP. Place it in dimethyl silicone oil with a magnet below, make the movable sheets tilt upward at a certain angle under the action of the magnetic field, heat it at 100 °C for 2 hours to dissolve and precipitate the polycaprolactone solution, and fill it with dimethyl silicone oil to obtain the microfluidic directional transport device.

[0080] (3) Take out the microfluidic directional transport device from the dimethyl silicone oil and use it for the control of droplet driving.

[0081] Under the action of an external magnetic field, the microfluidic directional transport device of this embodiment can complete Figures 2 to 5 dynamic digital display, chemical microreaction, anti-droplet icing, underwater bubble transportation, etc. as shown.

[0082] Comparative Example 1

[0083] This comparative example provides a microfluidic directional transport device, including a traditional magnetic cilia array and a lubricating fluid perfused at the bottom of the magnetic cilia array. Its preparation method includes the following steps:

[0084] (1) Prepare a magnetically controlled cilia array by using a simple one-step spraying method. Spray the solution on the substrate with a permanent magnet placed below for 30 s, and then put it into an oven at 60 °C for curing for 4 hours. The solution includes: 5 g of ethyl acetate, 2 g of PDMS and curing agent, and 2 g of CIP.

[0085] (2) The diameter of the cilia in the magnetically controlled cilia array is about 50 microns, the length is about 500 microns, and the cilia spacing is about 50 microns.

[0086] (3) Perfuse dimethyl silicone oil on the surface of the magnetically controlled cilia array containing cilia, so that the liquid level height of the dimethyl silicone oil is half of the length of the cilia, and a microfluidic directional transport device is obtained.

[0087] Statistically compare the elapse of the lubricating fluid in the microfluidic directional transport devices of Example 1 and Comparative Example 1, and the results are as Figure 6 shown. It can be Figure 6 seen that the microfluidic directional transport device of Example 1 can reduce the elapse speed of the lubricating fluid.

[0088] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A microfluidic directional transport device, characterized in that, Comprising: a substrate with grooves, a flexible polymer layer with a number of movable sheets, and a lubricating fluid; the flexible polymer layer and the annular protrusion on the surface of the substrate with grooves are connected to form a bag-like structure with a cavity; the lubricating fluid is filled in the cavity; the flexible polymer layer comprises a flexible polymer and magnetic particles distributed in the flexible polymer.

2. The microfluidic directional transport device according to claim 1, wherein The surface energy of the lubricating fluid is 15 - 40 mN / m, and the dielectric constant of the lubricating fluid is less than 15.

3. The microfluidic directional transport device according to claim 1, characterized in that The lubricating fluid is selected from one or more of dimethyl silicone oil, polydimethylsiloxane, mineral oil, castor oil, olive oil, and perfluoropolyether; and / or, the flexible polymer is selected from one or more of polydimethylsiloxane, polyethylene, polyurethane, and silicone rubber; and / or, the material of the magnetic particles is selected from one or more of Fe3O4, CIP, Gd-DTPA, SPIO, Gd2O3, FeCo, FeNi, Y2O3; the diameter of the magnetic particles is 1 - 10 μm.

4. The microfluidic directional transport device according to claim 1, characterized in that, The mass ratio of the flexible polymer to the magnetic particles is 1:(1 - 3); and / or, the thickness of the flexible polymer layer is 5 - 50 microns.

5. The microfluidic directional transport device according to claim 1, wherein The groove depth of the grooves is 50 - 500 microns.

6. The microfluidic directional transport device according to claim 1, wherein The shape of the movable sheets is selected from one or more of oval, rectangular, and triangular; and / or, the area of the movable sheets is 1000 - 10000 square microns; the spacing between the movable sheets is 80 - 200 microns.

7. The microfluidic directional transport device according to claim 1, characterized in that, The microfluidic directional transport device further comprises a magnetic driving device.

8. A method for preparing a microfluidic directional transport device according to any one of claims 1 to 7, characterized in that, Including steps: providing a substrate with grooves; thermally melting and solidifying polycaprolactone in the grooves to obtain a first intermediate; mixing magnetic particles and uncured flexible polymer to obtain a mixture; covering the mixture on the side of the first intermediate containing polycaprolactone and curing to form a flexible polymer layer to obtain a second intermediate; cutting a number of movable sheets on the flexible polymer layer of the second intermediate to obtain a third intermediate; placing the third intermediate in a lubricating fluid and heating in an externally magnetic field environment to discharge the polycaprolactone in the third intermediate and fill it with the lubricating fluid to obtain the microfluidic directional transport device.

9. The preparation method according to claim 8, characterized in that, In the step of cutting a number of movable sheets on the flexible polymer layer of the second intermediate, the cutting method is selected from one or more of focused ion beam cutting, femtosecond laser cutting, electron beam cutting, and atomic force microscope nano-cutting.

10. An application of the microfluidic directional transport device according to any one of claims 1 - 7 in droplet transportation, microchemical reactions, and dynamic digital displays.

Images