COPYRIGHT NOTICE

[0001] This patent disclosure may contain material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves any and all copyright rights.

INCORPORATION BY REFERENCE

[0002] All patents, patent applications and publications cited herein are hereby incorporated by reference in their entirety in order to more fully describe the state of the art as known to those skilled therein as of the date of the invention described herein.

FIELD OF THE INVENTION

[0003] The present application relates to microfiuidic devices. More particularly, the present application relates to preventing fouling in microfiuidic devices.

BACKGROUND

[0004] Advances in microfluidics are revolutionizing many traditional disciplines, such as molecular biology, drug discovery, medical diagnostics, and materials science. Despite their significance, the fouling of microfiuidic networks when components from fluids irreversibly adhere to channel surfaces, remains a challenging and unresolved issue despite over two decades of research. Various strategies have been proposed to prevent surface fouling, such as using polymers, glass, and metals to fabricate the microfiuidic channels or chemical modification of material surfaces. However, these conventional strategies have not yet yield a perfectly non-fouling surfaces. The following are some typical examples.

[0005] Glass is extremely chemically robust: it is resistant to corrosion and fouling, does not swell, and is compatible with a wide variety of chemicals, including organic solvents. Glass can also be functionalized to control surface properties, to graft desirable chemical groups to the surface or to spatially control wettability. For example, glass capillary devices can be functionalized to spatially control wettability and can form double and triple emulsions, even using organic solvents. However, glass devices are difficult to fabricate. Glass capillary devices require manual tip pulling to form the drop making nozzles and hand alignment to assemble the devices, tedious processes that are difficult to automate. Glass capillary can only be made to perform a small set of functions, such as forming drops. Moreover, glass microfluidics cannot be used for alkaline solution transport application. Glass is hydrophilic with a net negative charge, so substances with the opposite charge tend to stick to it. Hence, biofouling in marine environment as well as for medical diagnostic are critical issues for glass.

[0006] Silicon has a high elastic modulus (130-180 GPa) and is not easily made into active fluidic components such as valves and pumps. Silicon surface chemistry based on the silanol group (-Si-OH) is well developed, so modification is easily accomplished via silanes. Silicon is transparent to infrared but not visible light, making typical fluorescence detection or fluid imaging challenging for embedded structures. For silicon microfluidics, the nonspecific adsorption can be reduced or cellular growth improved through chemical modification of the surface.

[0007] Low-temperature cofired ceramic (LTCC) is an aluminum oxide based material that comes in laminate sheets that are patterned, assembled, and then fired at elevated temperature. Due to its laminar nature, LTCC can be fabricated into complex three- dimensional devices where each layer can be inspected for quality control before inclusion in the stack. Because the surface charge of LTCC is negative, there is an electrostatic adsorption of charged molecules in solution.

[0008] Polydimethylsiloxane (PDMS) is the most common microfluidic substrate in use in academic laboratories due to its reasonable cost, rapid fabrication, and ease of implementation. PDMS tends to be hydrophobic, so fouling can occur via hydrophobic interactions. The applications of PDMS chips are severely limited by a few drawbacks that are inherent to this material: (i) strong adsorption of molecules, particularly large biomolecules, onto its surface; (ii) absorption of nonpolar and weakly polar molecules into bulk PDMS; (iii) leaching of small molecules from bulk PDMS into solutions; and (iv) incompatibility with organic solvents. Therefore, special attention must be paid when quantitative analysis is needed (materials lost on channel walls and into the PDMS bulk) or organic solvents are involved.

[0009] TEFLON microfluidics shows good inertness to various chemicals and extreme resistance against all solvents. However, fouling problems still exist, especially for biological molecules. [0010] Poly(methyl methacrylate) (PMMA), formed through the polymerization of methyl methacrylate, is widely known under the commercial names of Plexiglas and Lucite. PMMA patterns can be formed through hot embossing or injection molding. Several different methods for bonding to form microfluidic networks have been demonstrated. Because the surface charge of PMMA is negative, there is an electrostatic adsorption of charged molecules in solution.

[0011] The incorporation of poly(ethylene glycol) (PEG) may help to reduce nonspecific adsorption of proteins and cells. A poly(ethylene glycol)diacrylate (PEGDA) material with resistance to permeation of small molecules and to nonspecific protein adsorption overtime was used to build micro fluidics. Although the PEG coatings are generally successful in suppressing nonspecific adsorption of proteins, they can cause undesirable secondary reactions.

[0012] Hence, these approaches have not effectively resolved the problem of fouling that occur in microfluidic devices.

SUMMARY

[0013] In accordance with certain embodiments, an antifouling microfluidic device is described. The antifouling device includes a microfluidic channel within a porous membrane, said microfluidic channel having at least one cross-section dimension that is between 0.1 to 500 μιη that defines a geometry for passage of a transport fluid, a lubricant stably infused within the porous membrane and filling the microfluidic channel, and first and second openings connected to said microfluidic channel that allows flow of a transport fluid into and out of said microfluidic channel..

[0014] In certain embodiments, an antifouling microfluidic device includes a lower porous membrane, an upper encapsulating material, a central porous membrane disposed between the upper encapsulating material and the lower porous membrane, a microfluidic channel that defines a geometry for passage of a transport fluid, wherein the upper encapsulating material, the central porous membrane and the lower porous membrane define the upper, lower and side walls of the microfluidic channel, wherein the microfluidic channel has at least one cross-section dimension that is between 0.1 to 500 μιη, a lubricant infused within the lower porous membrane and the central porous membrane and forming a smooth coating of the lubricant over the surfaces of each of the porous membranes inside the microfluidic channel, and first and second openings in the upper encapsulating material that allows flow of the transport fluid into and out of the microfluidic channel.

[0015] In certain embodiments, an antifouling microfluidic device includes a first porous membrane, a second porous membrane, a third porous membrane, a fourth porous membrane, and a fifth porous membrane, the second porous membrane disposed between the first and third porous membranes, the fourth porous membrane disposed between the third and fifth porous membranes, a first microfluidic channel that defines a geometry for passage of a transport fluid, wherein the first, second and third porous membranes define the upper, lower and side walls of the first microfluidic channel, and wherein the first microfluidic channel has at least one cross-section dimension that is between 0.1 to 500 μιη; a second microfluidic channel that defines a geometry for passage of the transport fluid, wherein the third, fourth and fifth porous membranes define the upper, lower and side walls of the second microfluidic channel, and wherein the second microfluidic channel has at least one cross-section dimension that is between 0.1 to 500 μιη; the first microfluidic channel and the second microfluidic channel being connected to each other, a lubricant infused within the first, second, third, fourth and fifth porous membranes and forming a smooth coating of the lubricant over the surfaces of each of the porous membranes inside the microfluidic channel, and first and second openings in the first porous membrane that allows flow of the transport fluid into and out of the first and second microfluidic channels.

[0016] In certain embodiments, the lubricant is immiscible with the transport fluid.

[0017] In certain embodiments, the lubricant wicks into, wets and stably adheres within the lower, upper, and central porous membranes.

[0018] In certain embodiments, the lower, upper and central porous membranes are preferentially wetted by the lubricant rather than by the transport fluid.

[0019] In certain embodiments, the lubricant has a higher dynamic viscosity than the dynamic viscosity of the transport fluid during steady-state flow.

[0020] In certain embodiments, the lubricant is a perfluorinated liquid, silicone, a hydrocarbon, an ionic liquid, or a food-grade oil.

[0021] In certain embodiments, said microfluidic device comprising said lubricant stably infused within the porous membrane provides a more transparent microfluidic device compared to the device without the lubricant.

[0022] In certain embodiments, the lower, upper and central porous membranes are selected from the group consisting of polytetrafluoroethylene, polypropylene, polycarbonate, polyester, polyethersulfone (PES), polyvinylidenedifluoride (PVDF), polydimethylsiloxane, metals (e.g., aluminum) and combinations thereof.

[0023] In certain embodiments, the transport fluid is a biological fluid.

[0024] In certain embodiments, the transport fluid is a microparticle- and nanoparticle- containing fluid.

[0025] In certain embodiments, the transport fluid is blood.

[0026] In certain embodiments, the antifouling microfiuidic device further includes an encapsulating material.

[0027] In certain embodiments, the encapsulating material is an optically clear, mechanically rigid structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other objects and advantages of the present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:

[0029] FIG. 1A shows a schematic illustration of the formation of a "slippery liquid- infused porous surface(s)" (SLIPS) microfiuidic device in accordance with certain embodiments;

[0030] FIG. IB is a zoomed-in schema of an inner surface of a SLIPS microfiuidic channel in accordance with certain embodiments;

[0031] FIG. 1C shows a tapered microfiuidic channel demonstrating that the lubricant refills the microfiuidic channel when flow of transport fluid is stopped in accordance with certain embodiments;

[0032] FIG. ID shows a conventional large scale flow cell where the opening between the walls are not filled with the lubricant;

[0033] FIG. 2A shows exemplary top, middle and bottom layer of a SLIPS microfiuidic device in accordance with certain embodiments;

[0034] FIG. 2B shows different microchannel geometries that can be formed in a SLIPS microfiuidic device in accordance with certain embodiments;

[0035] FIG. 2C shows different SLIPS microfiuidic devices in accordance with certain embodiments;

[0036] FIG. 2D shows the porous membrane of a SLIPS microfiuidic device being infused with a lubricant in accordance with certain embodiments; [0037] FIG. 3A shows optical image of polydimethylsiloxane (PDMS) microfluidic devices before injecting Rhodamine B water solution (RB) at (1), and fluorescent images of PDMS microfluidic devices before injecting RB at (2), after injecting RB at (3), and after injecting air at (4)in accordance with certain embodiments;

[0038] FIG. 3B shows optical image of TEFLON microfluidic devices before injecting RB at (1), fluorescent images of TEFLON microfluidic devices before injecting RB at (2), after injecting RB at (3), and after injecting air at (4)in accordance with certain embodiments;

[0039] FIG. 3Cshows fluorescent images of PDMS microfluidic device before injecting octane at (l)(with the optical image shown at top left), after injecting octane at (2), after injecting air(3), and after 15 min at (4) in accordance with certain embodiments;

[0040] FIG. 3Dshows optical image of TEFLON microfluidic device before injecting octane at (1), fluorescent images of TEFLON microfluidic devices before injecting octane at (2), after injecting octane at (3), after injecting air at (4) in accordance with certain embodiments;

[0041] FIG. 3E shows optical (1) and fluorescent (2) images of the SLIPS microfluidic device before injecting RB, after injecting RB at (3), after injecting air at (4), after injecting octane at (5), after injecting air at (6), after injecting octane for a second time at (7), and after injecting air yet again at (8) in accordance with certain embodiments;

[0042] FIG. 3F shows fluorescent image of the SLIPS microfluidic device before injecting RB (optical image at top left)(l), after infusing RB 10 μΕ/ηιίη for 1 hour (2), after infusing air 10 μΕ/ηιίη(3), after 12 hours and infusing RB 10 μΕ/ηιίη for 1 hour(4), after infusing air 10 μΕ/ηιίη, and tiny RB drops inside green circle(5), after infusing DI water 10 μΕ/ηιίη (6), after 18 hours and infusing RB 10 μΕ/ηιίη for 6 hours(7), after infusing air and DI water(8) in accordance with certain embodiments;

[0043] FIG. 4A shows 3D confocal images of two layers SLIPS microfluidic device fabricated with the hydroxy terminated PDMS lubricant (dye DFSB-K175) in accordance with certain embodiments;

[0044] FIG. 4B shows the optical and fluorescent merged images of a channel wall of the two layers PDMS lubricant SLIPS microfluidic device (1) before infusing water,(2)while infusing with wate infusing with water at 50 μΕ/ηιίη,(4) while infusing with water at 100 ng with water at 200 μΕ/ηιίη, and(6)after stopping the infusing of the water in accordance with certain embodiments;

[0045] FIG. 4Cshows a plot of the thickness variation of the lubricant layer of the channel wall of SLIPS microfluidic device in accordance with certain embodiments; [0046] FIG. 4D shows sectional confocal images of three layers SLIPS microfluidic device using a KRYTOX 103 lubricant. (1) shows infusing with RB at 10 μί/ηώι, (2) shows infusing with RB at 50 μί/ηώι, (3) shows infusing with RB at 100 μί/ηώι,(4) shows infusing with RB at 150 μΙ7ηιίη,(5) shows infusing with RB at 200 μί/ηώι, and (6) shows infusing with RB at 300 μΕ/ι ίη in accordance with certain embodiments;

[0047] FIG. 4E shows a plot of the thickness variation of the lubricant layer of the channel wall of SLIPS microfluidic device in accordance with certain embodiments;

[0048] FIG. 4F shows the confocal image of three layers SLIPS microchannel wall with KRYTOX 103 lubricant by infusing RB 10 μί/ιηίη and by infusing RB 200 μΕ/ι ίη (bottom), and the diagram of the transport mechanism of the microchannel (right)in accordance with certain embodiments;

[0049] FIG. 5A shows the resistance of the SLIPS microfluidic device from particles attachment in accordance with certain embodiments;

[0050] FIG. 5B shows a conventional TEFLON microfluidic device that suffers from particles attachment;

[0051] FIG. 6A shows the resistance of the SLIPS microfluidic device from proteins attachment in accordance with certain embodiments;

[0052] FIG. 6B shows a conventional TEFLON microfluidic device that suffers from proteins attachment;

[0053] FIG. 7A shows a fabricated SLIPS microfluidic device in accordance with certain embodiments;

[0054] FIG. 7B shows resistance of the SLIPS microfluidic device from attachment of blood after 1 hour in accordance with certain embodiments;

[0055] FIG. 7C shows a conventional TEFLON microfluidic device that suffers from attachment of blood after 1 hour in accordance with certain embodiments;

[0056] FIG. 7D shows resistance of the SLIPS microfluidic device from attachment of blood after7 hours in accordance with certain embodiments;

[0057] FIG. 7E shows a conventional TEFLON microfluidic device that suffers from attachment of bloodafter7 hours in accordance with certain embodiments;

[0058] FIG. 7F shows resistance of the SLIPS microfluidic device (the same sample used for 7 hours, FIG. 7D) from attachment of blood after 24 hours in accordance with certain embodiments;

[0059] FIG. 8A shows a photographic image of a multilayer SLIPS microfluidic device having microchannels in accordance with certain embodiments; [0060] FIGS. 8B and 8C show schematics of a design for multilayer SLIPS microfluidic device having microchannels in accordance with certain embodiments; and

[0061] FIGS. 8D and 8E show fluorescence images and the confocal images of multilayer SLIPS microfluidic device having microchannels infused with Rhodamine B aqueous solution in accordance with certain embodiments.

DETAILED DESCRIPTION

[0062] A universal antifouling microfluidic network that shows an outstanding inertness to various chemicals and organic solvents, resist adhesion from particles and proteins to complex fluids such as whole blood is described. The present approach is fundamentally different from the previous strategies in that a dynamic fluid surface that consists of a porous structured membrane infused with a lubricating fluid is utilized to create an antifouling layer (SLIPS). Therefore, the present design can provide a platform for many applications of microchannel systems and accelerate the development of high performance microfluidic devices. Moreover, the universality of the present approach in resisting fouling can also provide technological solutions to ultra-sensitive medical diagnostics and analytics, material synthesis, and industrial applications where sensitivity and performance cannot be compromised.

[0063] Microfluidics offers fundamentally new exciting capabilities in physicochemical synthesis, chemical and biological analysis, its broad applications are significantly limited by drawbacks of the materials used to make them. The fluid samples and the materials from which the microchannels are fabricated can all contribute to the problem that components from samples stick to the inner surfaces of microchannels, and the microfluidics' parts become encrusted, clogged, and eventually useless.

[0064] A microfluidic device refers to a device that includes one or more microfluidic channels designed to carry liquid samples, typically in volumes of less than one milliliter. In certain embodiments, the microfluidic device can include other elements, such as fluid inlets, fluid outlets, and valves that actuate the flow of fluids into (e.g., twist valves), out of, and/or through the microfluidic channels.

[0065] The microfluidic channel forms a path through the microfluidic device and generally has at least one cross-section dimension that is less than about 1 mm, such as in the range from about 0.1 micron to about 500 microns. In certain embodiments, the microfluidic channels can have lengths ranging from about a few microns to as long as 10 cm or even as long as several meters. The microfluidic channels may be linear in shape, or have any desired geometries, including curved, serpentine, spiraled, and the like. In certain instances, the microfluidic channels may intersect (e.g., cross-shaped intersections), diverge away (e.g., Y-shaped intersections, T-shaped intersection), or cross over one another.

[0066] In certain embodiments, the microfluidic device can have a total thickness between about a few tens of microns to a few tens of cm, such as between 10 micron to 2 cm, or 40 micron and 1 mm, and 70 to 500 micron.

[0067] In certain embodiments, the microfluidic device may further include a means to push fluid through the device, such as a syringe, a pump, a syringe pump, gravity, or combinations thereof. In certain embodiments, flow rate within the microfluidic device can range from about 0.01 μί/ηιίη to about 1 mL/min, more preferably from about 0.1 μί/ηιίη to about 500 μί/ηιίη. In certain cases, the flow rate ranges between about 10 μί/ηιίη and about

[0068] The microfluidic devices of the present disclosure (hereinafter "SLIPS microfluidic devices") includes a microfluidic channel located within one or more porous membrane, with one or more inlet ports for transport of a transport fluid through the microfluidic channel. The porous membrane is infused with a lubricant to form a smooth coating of the lubricant over the surfaces of the microfluidic channel.

[0069] In one embodiment, as shown in FIG. 1A, the microfluidic device includes a lower/bottom porous membrane, an upper/top porous membrane, a central/middle porous membrane disposed between the upper and lower porous membranes. The microfluidic device may further include a channel that defines a geometry for passage of a transport fluid, wherein the upper, central and lower porous membranes define the upper, lower and side walls of a microfluidic channel. The microfluidic device further includes a lubricant infused within the lower porous membrane, the central porous membrane and the upper porous membrane and forming a smooth coating of the lubricant over the surfaces of each of the porous membranes inside the microfluidic channel. The microfluidic device includes first and second openings in the upper porous membrane that allows fluid flow into and out of the microfluidic channel. This concept can be generalized to multiple layers of channels to create a three dimensional microfluidics systems, where the transport fluid can enter from the device inlet, and pass through the channels in each layers and exit at the device outlet.

[0070] FIG. IB shows a zoomed in scheme near the microfluidic channel wall where the porous membrane, the lubricant and the transporting liquid is shown. [0071] The SLIPS microfluidic devices can designed based on the following criteria: (1) the antifouling layer of the lubricant and the transport fiuids are immiscible, and (2) the lubricant wicks into, wets and stably adheres within the porous membranes, and the membranes are preferentially wetted by the lubricant rather than by the transport fluids. In certain embodiments, a third criteria may be met where (3) the lubricant should avoid being taken away by the transport fiuids during the steady-state transport.

[0072] The first requirement can be achieved easily by the law of similarity and intermiscibility.

[0073] The second requirements can be satisfied by using micro/nano porous membranes whose large surface area, combined with chemical affinity for the fluids, facilitates complete wetting by, and adhesion of, the lubricant.

[0074] To satisfy the third criterion— the lubricant can be made much more viscous than the transport fiuids, so that for various realistic flow rates of the fiuids, along the direction of the fluid transport, the movement of the lubricant is nearly negligible.

[0075] In certain embodiments, the porous membranes may be formed using any suitable porous material, such as a TEFLON, porous membrane. In other embodiments, the porous membranes may include PDMS, glass, silicon, LTCC, polypropylene, metallic (e.g., silver, aluminum), carbon, polyester (PETE), polyethersulfone (PES), polyvinylidenedifluoride (PVDF), Nylon, cellulose, and the like.

[0076] In certain embodiments, the porous membranes may be chemically functionalized with one or more functional groups that provide improved affinity with the lubricant to allow the lubricant to be stably immobilized therein.

[0077] In certain embodiments, the lubricant can be selected from any suitable material, such as a broad range of perfiuorinated fiuids (including but not limiting to the tertiary perfiuoroalkylamines (such as perfiuorotri-n-pentylamine, FC-70 by 3M, perfiuorotri-n- butylamine FC-40, etc.), perfluoroalkylsulfides and perfiuoroalkylsulfoxides, perfiuoroalkylethers, perfluorocycloethers (like FC-77) and perfluoropolyethers (such as KRYTOX family of lubricants by DuPont), perfluoroalkylphosphines and perfiuoroalkylphosphine oxides as well as their mixtures can be used for these applications); polydimethylsiloxane and their functional modifications; food compatible liquids (including but not limiting to olive oil, canola oil, coconut oil, corn oil, rice bran oil, cottonseed oil, grape seed oil, hemp oil, mustard oil, palm oil, peanut oil, pumpkin seed oil, saffiower oil, sesame oil, soybean oil, sunflower oil, tea seed oil, walnut oil, and a mixtures of any of the above oils), as well as ionic liquids. [0078] In certain embodiments, the transport fluid can be various simple and complex fluids, such as water, acids, alkaline, salt solutions, particle-suspending solutions, crude oil, blood, urine, saliva, DNA, RNA, and proteins solutions, and the like.

[0079] In certain embodiments, the channel/openings may be formed by any suitable methods, such as laser cutting. In other embodiments, the channel/openings may be formed by blade cutting, photolithography and thermo or compression molding technique.

[0080] In certain embodiments, the device may be fully encapsulated in an encapsulating material, such as PMMA. In other embodiments, the encapsulating material may include glass, ceramics and metal.

[0081] In certain embodiments, the device may be assembled by stacking multiple layers of porous membranes, or by folding the porous membrane in the form of origami, which can then be encapsulated in the aforementioned encapsulating materials.

[0082] Many different methods to infuse the porous membrane with a lubricant will be within the scope of one of ordinary skill in the art.

[0083] In certain embodiments, the porous membrane can be infused with a lubricant by submerging the microfluidic device into a bath of a lubricant. In yet other embodiments, the porous membrane can be infused with a lubricant by soaking the porous membrane prior to assembly of the SLIPS microfluidic device.

[0084] In certain embodiments, the porous membrane can be infused with a lubricant using the one or more inlets before the transport fluid is passed through the SLIPS microfluidic device. In such embodiments, the microfluidic channel may have at least one cross section dimensions that are less than 1 mm, such as any range from about 0.1 micron to about 1000 microns, 0.1 micron to about 500 microns, or the like. In such embodiments, the microfluidic channel may be completely filled with the lubricant until the transport fluid is introduced into the microfluidic channel, whereby the lubricant filling the channel is displaced by the transport fluid. Nevertheless, as the transport fluid displaces and flows through channels, the microfluidic channel may maintain a thin layer of lubricant layer over the porous membrane that form the walls of the microfluidic channel.

[0085] Without wishing to be bound by theory, when the microfluidic channels are less than a certain size scale, e.g., less than 1 mm, lubricant may fill the entirety of the microchannel when no transport fluid pass through the channels. As the transport fluid is introduced into the channels, the lubricant may be pushed backward inside the membrane. This effect may become more pronounced with increasing flow rate. While decreasing the flow rate, the lubricant may come back inside the channel, and finally seal the channel whenever the flow stops.

[0086] Specifically, increasing the liquid flow rate (or the pressure) of the transport fluid through the channel, the thickness of the lubricant layer may be altered. However, above a certain flow rate (e.g., above 150 μΕ/ηώι for the examples described below), the thickness of the lubricant layer becomes very thin, but nearly unchanged. Without wishing to be bound by theory, a minimum lubricant layer thickness may be reached because the membrane is preferentially wetted by the lubricant rather than the transport fluid.

[0087] When the flow of the transport fluid is stopped, the lubricant may refill the entire cross section of the microfluidic channel.

[0088] It should be noted that microfluidic channels having a dimension that exceeds 1 mm may not allow refilling of the entire cross section of the microfluidic channel, which can then lead to loss of some of the advantageous properties more fully discussed below (e.g., transparency, ability to clean out channels, etc.). For example, FIG. 1C shows a tapered microfluidic channel that is about 200 micrometers in height and varies in width up to about 1 mm. As shown, the lubricant fills the entire channel when no transport fluid (e.g., water) passes through the channel (see "Before" image). When water is introduced at a rate of 100 μυηώι, only a thin layer of lubricant remains near the walls of the microfluidic channels (see thin gray regions near the wall in "After infusing water" image). When water flow is stopped and the pressure released, the lubricant refills the entire channel (see "Stop and release the pressure inside the channel") image.

[0089] In contrast, as shown in FIG. ID, when a Tygon tube of inner diameter 3 mm was mounted in a peristaltic pump and connected to a dual-chamber 3D-printed flow cell (chamber dimensions of 1 = 10 cm, w = 1 cm and h = 1 mm), complete filling of the region between the walls does not occur.

[0090] Such an ability to refill the entirety of the microfluidic channel can provide further interesting and beneficial applications. For example, by recognizing that a certain flow rate provides the minimum lubricant layer thickness, transport fluid containing a material of interest can be flowed through the microchannel device at a flow rate that provides a lubricant layer that is sufficiently thicker than the minimum lubricant layer thickness. Despite the exceptional anti-fouling capability of the SLIPS microfluidic devices, if any materials becomes attached to the microfluidic channels (e.g., due to extremely long or harsh operating conditions), a "cleaning fluid" can be then sent through the channel at a higher flow rate so that any materials that may have become attached can be easily removed. Accordingly, the SLIPS microfluidic devices can be easily cleaned of any undesired, stuck material.

[0091] Alternatively, the transport liquid may be flowed through at a flow rate that provides the minimum lubricant layer thickness to (relatively speaking) promote attachment of certain desired materials that may be included in the transport fluid (e.g., preferentially allow certain materials inside the transport fluid to stick while other components continue to pass through). Then, when a sufficient amount of the material has been attached to the walls of the microfluidic channels, a "collection fluid" can be flowed through at a lower flow rate, which will increase the lubricant layer, leading to the attached materials to become unattached. Then, these materials can be collected within the collection fluid and collected accordingly.

[0092] Such applications, as well as others, can be envisioned by the use of the microfluidic devices described herein, where the effective width of the slippery microfluidic channel can be tuned as desired based on the flow rate of the transport liquid. In return, it may provide further ability to tune the degree of slipperiness as desired.

ADVANTAGES

[0093] The SLIPS microfluidic device may provide a number of advantages. First, the SLIPS microfluidic device does not suffer from fouling as in conventional microfluidic devices. Second, the SLIPS microfluidic device can provide a slippery channel sidewall so that plug flow conditions can arise, providing little resistance to the flow of the transport fluid. Third, the fully porous material nature of the device allows the lubricant to continuously replenish to the surface of the channel sidewall, leading to self-healing and self- lubrication actions for surface renewal.

[0094] More specifically, the SLIPS microfluidic devices described herein provide a simple and universal solution for antifouling within a fluidic network, and this strategy can be applied to a broad variety of channels within low-surface-energy porous/textured materials, infused with a low surface tension (e.g., fluorinated) liquid. The lubricating liquid is locked in place by the low-surface-energy structured membrane and provides a stable "antifouling" interface that can operate in various channels' shapes of microfluidics.

[0095] Moreover, the SLIPS microfluidic devices described herein provide an impressive antifouling property against both polar and non-polar liquids. In contrast, under the same conditions, significant fouling is observed for typical engineering materials used for microfluidics, such as PDMS and Teflon. For example, the liquid hydrocarbons of lower surface tension (Octane) is very easy to damage the PDMS microfluidics and soak the entire Teflon microfluidics. The SLIPS microfluidic devices described herein do not exhibit such problems associated with conventional microfluidic devices.

[0096] Particles transport inside microchannels has its difficulties due to wall attachment of particles and following fouling and blocking of the passages. Adsorption of proteins onto surfaces of microchannels can result in denaturing of proteins and consumption of precious samples. Traditional superhydrophobic channels have limited antifouling capability as fouling will typically be induced by the strong hydrophobic interaction between the surface and the hydrophobic portion of biomolecules. Moreover, these microfluidic channels have shown limited capability to handle complex biological fluids, such as whole blood. The SLIPS microfluidic devices described herein show excellent antifouling against various complex liquid mixtures, such as particles, proteins, and whole blood, that rapidly foul any existing microfluidics. In contrast, even though Teflon-based microfluidic channel had been reported to have extreme resistance against all solvents, particles, proteins and blood can still contaminate the Teflon microfluidic channels.

[0097] The SLIPS microfluidic devices provide antifouling properties for a much longer duration than any of the conventional microfluidic devices. For example, the bioinspired channels do not show degradation or fouling after multiple uses for an extended period of time, e.g., greater than 1, 2, 3, 4, 5 6 or even longer hours of continuous operations.

[0098] Transparent omniphobic microfluidic devices have not yet been reported in the literature. To this end, the SLIPS microfluidic devices described herein not only possesses antifouling and omniphobic characteristics, but they can also be tuned optically transparent by infusing lubricant with matching optical refractive index with the porous solid materials. This property allows for the detection of optical signals through the channel materials, such as fluorescence signals.

EXAMPLES

[0099] The following methods and materials were utilized for the following examples, which are meant to illustrate, and not limit, the scope of the invention.

MATERIALS

[0100] TEFLON porous membranes: There are two types of TEFLON membranes purchased from Sterlitech Corporation, WA, USA. The first one is the membrane with average pore size of > 5 μιη and thickness of -200 μιη. The second one is the membrane with average pore size of > 200 nm and thickness of ~30 μηι. These membranes were evaluated by scanning electron micrograph and contact angle measurements. For the confocal measurements described below, the second one was thinner as the top layer to get better fluorescent signal of the liquid transport inside the microchannel.

[0101] PDMS channels: SYLGARD 184 SILICONE ELASTOMER BASE and SYLGARD 184 SILICONE ELASTOMER CURING AGENT were purchased from Dow coming corporation. PDMS mixed at a 10:1 curing ratio is placed into microfluidic molds and cured for 3 hours at 70 °C.

[0102] PMMA sheets: The scratch-resistant clear cast acrylic sheet 1/16" thick, 12" X 12" and the scratch-resistant clear cast acrylic sheet 3/16" thick, 12" X 12" were purchased from McMaster Carr Supply Company.

[0103] The lubricant used for the experiments were KRYTOX 103 and the hydroxyl terminated PDMS lubricant (dye DFSB-K175). Unless otherwise specified, KRYTOX 103 was used throughout the antifouling experiments. PDMS lubricant with dye was used for the two layers SLIPS microchannel experiments to obtain the optimal 3D confocal fluorescent signal detection. Deionized water with a resistivity of 18.3 ΜΩ-cm was used for the measurements.

[0104] The transport fluids were obtained from Sigma Aldrich which include octane (puriss, > 99.0%) and Rhodamine B (HPLC, > 97.0%). Dye DFSB-K175 was obtained from www.riskreactor.com.

[0105] Interfacial dynamics microparticles in the suspension are the surfactant-free fluorescent yellow green sulfate latex which was obtained from Invitrogen, and the diameter is -1.6 μιη (8ο1ίά%: 1.9).

[0106] Fluorescein conjugated bovine serum albumin (BSA) was obtained from Molecular Probes® in Fraction V, BSA from J.T. Baker®. Phosphate buffered saline (PBS) was obtained from Biowittaker®. Sheep blood in heparin (3 IU/mL) was obtained from HemoStat Laboratories, CA, USA.

[0107] Rhodamine B water solution (RB): Rhodamine B was dissolved in a DI water to give the RB solution a final concentration of 0.1 mg/mL.

[0108] Fluorescent lower surface tension organic liquid: Dye DFSB-K175 was dissolved in octane with 0.10 Vol%.

[0109] Fluorescent particles suspending solution: The suspension was for 0.1 mL of a 1.9%) suspension in 2 mL H ₂ 0, so it is approximately a 0.10 Vol%> suspension. [0110] Fluorescently labeled protein solution: The solution was made with 1% fluorescein conjugated BSA, and it was diluted in IX PBS to a final total protein concentration of 1%.

MICROCHANNELS PREPARATION

[0111] Here a convenient approach for the fabrication of the SLIPS microfluidic device is shown. First, various software can be utilized to design the channel pattern with extremely high resolution and fidelity for different applications.

[0112] Versalaser cutting engraving system (CNS, Harvard University) was used to cut the channels or ports on the membrane directly, and it takes less than 15 seconds for each membrane. After obtaining the optimal cutting parameters for different membrane materials, good channels were obtained on the porous membranes, otherwise the membrane can be destroyed by the excessive laser energy.

[0113] However, the preparation of the channels on the membranes has almost no restrictions, and it is compatible with various other technologies to make all kinds of shapes of channels besides laser cutting, such as blade cutting, photolithography, and thermo and compression molding technique. In certain embodiments, clean room and other equipment such as photolithography followed by selective etching can be utilized.

[0114] Second, transparent PMMA sheets and stainless steel screws were used to provide very stable seal performance of the three or two layers SLIPS microfluidic devices to avoid any leaking of the lubricant and/or the transport fluid.

[0115] Third, the lubricant was infused inside the microfluidic channel, and the transparency of the microchannels increased significantly.

[0116] Finally, various transport fluids were introduced inside the microchannels to evaluate the antifouling performance of the SLIPS microfluidic device. For various transport fluids inside the microchannels, the transport fluids were driven by a fluid delivery syringe pump (Harvard Apparatus' PHD ULTRA CP Syringe Pump) equipped with syringes (NORM-JECT).

[0117] With this approach, various complex microchannel's shapes can be generated in the microfluidics, which makes it ideal for a variety of specific applications in future. Moreover, the fabrication process is convenient and also amenable for mass production of real-world applications. And the SLIPS microfluidic device can be recycled for multiple uses without risk of contamination. CONTACT ANGLE MEASUREMENTS

[0118] The contact angle measurements were performed by a contact angle measurement system (KSV CAM 101) at room temperature (i.e., 20 - 24 °C) with -20% relative humidity. The system was calibrated before all the measurements were taken. The macroscopic droplet profile was captured through a camera equipped with an optical system for amplification of the captured image, where the droplet was fitted into a spherical cap profile by a computer program provided from the system in order to determine the advancing and receding angles, and the droplet volume. In measuring the contact angle hysteresis (i.e., difference between the advancing and receding angles), the droplet volume was increased/reduced until the contact line advances/recedes for the measurement of advancing/receding angles. The accuracy of the contact angle measurements is -0.1°. The sliding angle of the droplet was measured by a tilting stage with a resolution of 0.5°.

FLUORESCENT MEASUREMENTS

[0119] Zeiss Confocal Laser Scanning Microscope from Carl Zeiss Microscopy GmbH, Jena, Germany, (LSM 700) was used in the fluorescent and confocal experiments. For dye RB and fluorescently labeled protein (fluorescein), the measuring parameters were directly automatic set-up from the database of Zeiss microscopy system. The dye DFSB-K175 was detected for a broad wavelength range (> 560 nm), and laser line (488 nm). The fluorescent particles were detected for a broad wavelength range (> 500 nm), and laser line (488 nm).

EXAMPLE 1

[0120] A series of microfluidic devices were fabricated to study both the antifouling and transport properties of the microchannels. As shown in FIG. 2 A, three layers microchannel membranes were prepared by using a laser cutting technology. As shown in FIG. 2B, the laser cutting technique allows control over the shapes of the microchannel, and it can easily provide a stable "antifouling" interface that can operate in diversified channels' shapes of microfluidics from simple regular to complex irregular. Thereafter, as shown in FIG. 2C(showing various different shapes of the microchannel), an encapsulating material can be provided around the porous membranes and provided with desired inlet and outlet ports. Moreover, as shown in FIG. 2D, by infusing the lubricant inside the porous membrane through the inlet port, the transparency of the microchannels increased significantly. It should be noted that as shown in FIG. 1A, the infusing of the lubricant and the flow of transport liquid inside the microfluidic channel may be reversible. [0121] To get better fluorescent signal of the fluids inside the microchannel, two types of TEFLON porous membranes were tested (Sterlitech Corporation): (1) porosity 5 μιη, thickness 200 μι ^η , < _sta tic 142.8± 2.0°, < _s iidin _g 20.2± 4.4° and (2) porosity 200 nm, thickness 30 μιη, 6 _C 138.7 ± 3.21°, 6> _slldmg 30.3 ± 0.7°.

[0122] For the lubricant, low-surface-tension liquids (DUPONT KRYTOX 103, γ = 17.6± 0.3 mN m ^"1 and the hydroxyl terminated PDMS, γ = 19.4± O. lmN m ^"1 ) that were utilized. The selected lubricants are immiscible with both aqueous and hydrocarbon phases and therefore able to form a stable, antifouling interface when infused into the porous membrane. After infusing with the lubricant, extreme liquid repellency were observed as signified by very low sliding angles (9 _s mmg ^< 5°) (see Table 1 below).

Tablet. Measured "sli er " ro erties of TEFLON membrane and SLIPSmembrane.

[0123] The universal antifouling properties of this SLIPS microfluidics were evaluated by measuring the fluorescent signals of the microchannels. Here PDMS microfluidics and whole-TEFLON microfluidics were selected as controls because both PDMS microchannels and TEFLON microchannels are well developed and typically and commonly used for microfluidics applications.

[0124] FIG. 3A shows optical image of polydimethylsiloxane (PDMS) microfluidic devices before injecting Rhodamine B water solution (RB) at (1), and fluorescent images of PDMS microfluidic devices before injecting RB at (2), after injecting RB at (3), and after injecting air at (4);

[0125] FIG. 3B shows optical image of TEFLON microfluidic devices before injecting RB at (1), fluorescent images of TEFLON microfluidic devices before injecting RB at (2), after injecting RB at (3), and after injecting air at (4); [0126] FIG. 3Cshows fluorescent images of PDMS microfluidic device before injecting octane at (l)(with the optical image shown at top left), after injecting octane at (2), after injecting air(3), and after 15 min at (4);

[0127] FIG. 3Dshows optical image of TEFLON microfluidic device before injecting octane at (l),fluorescent images of TEFLON microfluidic devices before injecting octane at

(2) , after injecting octane at (3), after injecting air at (4);

[0128] As shown in FIGS. 3A and 3B, a significant amount of the residual RB are observed on both the walls of a PDMS channel (FIG. 3A) and a TEFLON channel (FIG. 3B)after RB transport inside the microchannels. Especially, as shown in FIGS. 3Cand 3D, octane is very easy to damage the PDMS microfluidics (FIG. 3C) and soak the entire TEFLON microfluidics (FIG. 3D), scale bar 100 μπι.

[0129] In contrast, under the same conditions, SLIPS microfluidic device shows excellent resistance to RB and octane. FIG. 3E shows optical (1) and fluorescent images of the SLIPS microfluidic device before injecting RB(2), after injecting RB(3), after injecting air(4), after injecting octane (5), after injecting air(6), after injecting octane for a second time (7), and after injecting air yet again (8). As shown in FIG. 3E, no fouling and soaking of the channel can be observed after twice infusing octane, scale bar 100 μιη.

[0130] The antifouling duration of the SLIPS microfluidic device against RB fouling was studied. The SLIPS microfluidic device was infused with a 100 μ i L RB for 1 hour. FIG. 3F shows fluorescent image of the SLIPS microfluidic device before injecting RB (optical image at top left) (1), after infusing RB 10 μΕ/ηιίη for 1 hour (2), after infusing air 10 μΕ/ηιίη

(3) ,after 12 hours and infusing RB 10 μΕ/ηιίη for 1 hour (4), after infusing air 10 μΕ/ηιίη, and tiny RB drops inside green circle (5), after infusing DI water 10 μΕ/ηιίη (6), after 18 hours and infusing RB 10 μΕ/ηιίη for 6 hours (7), after infusing air and DI water (8), scale bar 100 μιη.

[0131] As shown, after injecting the microfluidic channel with air, no fluorescent signal against background can be seen on the wall of the channel under a fluorescent microscope, scale bar 100 μιη. (FIG. 3F (1-3)) After 12 hours, the channel was infused with RB again for 1 hour. (FIG. 3F (4)) After injecting the channel with air, there were several tiny inconspicuous RB drops inside the channel. (FIG. 3F (5))After washing with DI water, no fluorescent signal can be seen on the wall of the channel. (FIG. 3F(6)) After 18 hours, the channel was infused with RB again for 6 hours. After injecting the channel with air and washing with DI water, no fluorescent signal can be seen on the wall of the channel, and this super cleanness of the SLIPS microfluidic device is of great importance to quantitative analysis application.

[0132] The fluid transport properties were determined by ZEISS confocal microscopy system. FIG. 4A shows 3D confocal images of two layers SLIPS microfluidic device fabricated with the hydroxy terminated PDMS lubricant (dye DFSB-K175). (1) shows the SLIPS microfluidic device before infusing with DI water. (2) shows the SLIPS microfluidic device after infusing with DI water at 200 μί/ηιίη. (3) shows the SLIPS microfluidic device after the infusement with DI water was stopped. As shown, infusing the SLIPS microfluidic device with the DI water is a reversible process.

[0133] FIG. 4B shows the optical and fluorescent merged images of a wall of the two layers PDMS SLIPS microfluidic device (1) before infusing water, (2) while infusing with water at 10 μί/ιηίη (3) while infusing with water at 50 μί/ηιίη, (4) while infusing with water at 100 μί/ηιίη, (5) while infusing with water at 200 μί/ηιίη, and (6) after stopping the infusing of the water. Scale bar is 20 μιη. As shown, the results reveal the thickness of the antifouling lubricant layer decreases by increasing the liquid flow rate from 10 to 200 μί/ηιίη. The thickness variation of the lubricant layer of the channel wall is plotted in FIG. 4C and indicates that when the flow rate reached a certain level, and the decrease of the lubricant layer was nearly kept unchanged. The inset represents measured position 1, 2, 3 and 4of the channel, scale bar 200 μιη. On the other aspect, the change of the cross-sectional size of transport fluid inside the channel is equivalent to the thickness variation of the lubricant layer with different flow rates, because the antifouling layer of the lubricant and the transport fluid are immiscible.

[0134] FIG. 4D shows sectional confocal images of three layers SLIPS microfluidic device using a K YTOX 103 lubricant, (l)shows infusing with RB at 10 μί/ηιίη, (2) shows infusing with R infusing with RB at 100 infusing with RB at 150 g with RB at 200 μί/ηιίη, and (6)shows infusing with RB at 300 μί/ηιίη. Scale bar is 50 μιη. As with the two layers SLIPS microfluidic device, the thickness variation of RB as the transport liquid inside the microchannel with different flow rates was plotted in FIG. 4E. The inset represents measured position 1, 2, 3 and 4of the channel, scale bar 120 μιη. As shown, the change of the cross-sectional size of liquid with different flow rates shows the same trend as that of the two layers SLIPS microfluidic device. As such, the thickness of the antifouling lubricant layer appears to decrease by increasing the flow rates of the transport liquid, (see FIG. 4F, left) and when the flow rate reached a certain level, the decrease of the lubricant layer was kept nearly unchanged (see FIGS. 4C and 4E).

[0135] Without wishing to be bound by theory, based on these results, the lubricant layer appears to cover the porous structure membrane which serves as a reservoir of the lubricant. Initially, the lubricant may fill all of the microchannel. By increasing the liquid flow rate, the lubricant may be pushed backward inside the membrane. While decreasing the flow rate, the lubricant may come back inside the channel, and finally seal the channel whenever the flow stops.

[0136] For the particular examples described herein, when the flow rate is above 150 μυηιίη, the thickness of the lubricant layer becomes very thin. For this state, the thickness of the lubricant layer is kept nearly unchanged, likely because the membrane is preferentially wetted by the lubricant rather than the fluid, (see Tables 2 and 3 below)

Table3. Measured interfacial tension between water and lubricant.

[0137] Moreover, the minimum thickness of the lubricant may be determined by the intermolecular force between the lubricant and the membrane. Further increasing the flow rate may not lead to further decrease of the lubricant layer thickness due to the liquid-liquid super smooth surface which keeps refreshing to prevent the fluid fouling.

[0138] In order to achieve the stable antifouling lubricant layer, along the direction of the fluid transport, the movement of the lubricant is desirably as small as possible. During the steady-state transport, the shear stress ^τ should be continuous across the liquid-liquid interface. Therefore, it has the following scaling relation: R

Here ^f , ¹ are the dynamic viscosity of the transport fluid and the lubricant respectively. Typically, the dynamic viscosity of the transport fluid is smaller than the dynamic viscosity of the lubricant. In certain embodiments, the dynamic viscosity of the transport fluid is smaller than the dynamic viscosity of the lubricant with more than two orders of magnitude.

For example, at 20 °C, water, ^ =1.00xl0 ^"3 Pa s vs K YTOX 103, ^l = 1.4210x ^_1 Pa s; Blood, ^ =1.00x l0- ² Pa-s vs. KRYTOX 106, =1.46 Pa-s; see Table 4).

Table 4. D namic viscosit of various li uids.

^ ^f and ^ ¹ are the characteristic velocity of the two liquids. ^ is the scale of radius of the transport liquid, while ^ is the scale of thickness of the lubricant layer. According to the fluorescent measurement, for typical flow rates, t is smaller than R with more than one order of magnitude, when the liquid flow rate is more than or equal to 10 μΤ/ηιίη, ^{t <} ~ ^ ^;£/m and R > ~60 ^/ m Hence, typically, U; is smaller than tT/with more than three orders of magnitude, which means the antifouling lubricant layer can be effectively stationary relative to the transport fluid layer.

EXAMPLE 2

[0139] Particles transport inside conventional microchannels can foul easily due to the attachment of the particles to the sidewall and may lead to blockage of the passages. However, the SLIPS microfluidic device shows excellent resistance to particle attachment. FIG. 5A (1) shows micro particles with fluorescent signal in DI water solution. FIG. 5A (2- 10) shows fluorescent images of both the adjacent top and bottom layers of the SLIPS microfluidic device before and after infusing the channel with the solution of particles (endurance time: 15 min). No fouling of the channel can be observed after the repeated trials, (see FIG. 5A (11, 12)) In contrast, under the same conditions, when a conventional TEFLON channel microfluidic device is utilized, FIG. 5B (1-4) show that a significant amount of the particles is observed on the adjacent bottom layer of the two layers TEFLON channel.

EXAMPLE 3

[0140] The interest in microfluidics has increased rapidly for biological assay. However, biofouling of the microfluidics is a major problem. For example, adsorption of proteins onto surfaces of microchannels can result in the denaturing of the proteins and consumption of precious samples. Traditional antifouling capability of superhydrophobic surfaces of the channel is limited by the strong hydrophobic interaction between the surface and the hydrophobic portion of biomolecules. Therefore, this antifouling effect usually requires a constant presence of liquid flow, which is not always available for the microfluidics, especially when it is often paused.

[0141] The antifouling properties of the SLIPS microfluidic devices have been tested by infusing BSA protein solution as the transport fluid and repeatedly pausing the flow of the transport fluid. As expected, the microchannel shows excellent resistance to protein solution, and no fluorescent signal against background can be seen on the wall of the channel under a fluorescent microscope, (see FIG. 6A (1-12)) In contrast, under the same conditions, when a conventional microfluidic device made of TEFLON was utilized, a significant amount of the protein is observed on the adjacent bottom layer of the TEFLON channel, (endurance time: 15 min, FIG. 6B (1-4)).

[0142] As shown, the SLIPS microfluidic devices described herein exhibit an impressive antifouling property against both polar and non-polar liquids. In contrast, under the same conditions, significant fouling is observed for typical engineering materials used for microfluidics, such as PDMS and Teflon. Especially, the liquid hydrocarbons of lower surface tension (Octane) is very easy to damage the PDMS microfluidics and soak the entire Teflon microfluidics.

EXAMPLE 4

[0143] In addition, with whole blood transport, blood contains various biomolecules that exhibit a range of properties, such as protein adsorption from blood serum to the solid channel walls, known as the Vroman effect. In other words, fouling is dynamic in nature. A new generation of microfluidics promises to create experimental devices that, by measuring the flow of blood through tiny channels, can reliably predict how severe an individual's illness will be. However, due to the biofouling problems, these microfluidic channels have thus far shown limited capability to deal with the fluid complexity of milliliter amounts of whole blood samples. FIG. 7A shows the SLIPS microfluidic device. The antifouling properties have been studied by infusing sheep whole blood with different time. After infusing blood for 1 hour, no residual blood can be seen on the SLIPS membranes (FIG. 7B (1-4)), but there is still visible blood stain on the TEFLON membranes after rinsing by DI water. (FIG. 7C (1-4)) After infusing blood for 7 hours, there are several tiny inconspicuous blood drops on the membranes of the SLIPS microfluidic device, and after rinsing by DI water no residual blood can be seen on the membranes. (FIG. 7D (1-8)) In contrast, under the same conditions, a significant amount of the blood drops are observed on the TEFLON membranes, and after rinsing by DI water there are still very clear blood stain on the membranes. (FIG. 7E (1-8)) Furthermore, the membranes of the SLIPS microfluidic device in the 7 hours test was re-utilized by rebuilding and adding the lubricant for another long time test. FIG. 7F shows the membranes of the SLIPS microfluidic device after a 24 hours test and rinsing by DI water. As shown, no residual blood can be seen on the membranes, which means it could potentially promote a platform for the new generation of microfluidics for biomedical application.

EXAMPLE 5

[0144] FIGS. 8A through 8E show the design and images of a multilayer SLIPS microfluidic device having microchannels on three different layers which are in fluid communication with one another. FIG. 8A shows a top view photographic image of a multilayer SLIPS microfluidic device having an inlet and an outlet. FIGS. 8B and 8C show schematics of a design for multilayer SLIPS microfluidic device having microchannels on different layers and how they are in fluid communication with one another. The constructed multilayer SLIPS microfluidic device was then infused with Rhodamine B aqueous solution and FIGS. 8D and 8E show the resulting fluorescence images and the confocal images. As shown, Pvhodamine B is present in the microfluidic channels residing in 2 ^nd , 4 ^th and 6 ^th layer. The rectangular boxes in FIG. 8B indicate where these images were obtained.

[0145] In summary, the SLIPS microfluidic device of the present disclosure displays outstanding antifouling behavior. Any desired microfluidic channels can be prepared without restriction, and it is compatible with various technologies for making any desired shapes of channels, such as laser cutting, blade cutting, photolithography and thermo molding techniques. The SLIPS microfluidics can be constructed into 1-D, 2-D, and 3-D systems by stacking multiple layers of the channel-containing porous membranes. The material are also very simple with many existing membranes and lubricants already used for slippery surface applications. Therefore, the SLIPS microfluidic device can be easily achieved without extraordinary care or preparation which will benefit its large area application. As microfluidics research continues to push the limits, having various strategies to prevent fouling will become more critical. The SLIPS microfluidic device described herein and the broader application of microfluidic antifouling strategies hold significant promise for a broad range of industrial and biomedical products, and for providing a basic platform aimed at the development of biomimetic smart channel fluid systems.

[0146] Upon review of the description and embodiments provided herein, those skilled in the art will understand that modifications and equivalent substitutions may be performed in carrying out the invention without departing from the essence of the invention. Thus, the invention is not meant to be limiting by the embodiments described explicitly above.