Fabricating hybrid wettability surfaces

Abstract

A method for manufacturing a micro-model having a mixed wettability surface representative of a reservoir is disclosed. The method comprises: coating a top surface of a hydrophilic substrate with a photoresist; covering the top of the photoresist with a photomask; exposing the covered top of the photoresist to UV light that changes a chemical property of a region of the photoresist corresponding to the pattern of the photomask; removing the photomask; removing a region of the photoresist corresponding to the pattern of the photomask based on a chemical property of the region; depositing a hydrophobic film on the top of the hydrophilic substrate; and removing the remaining photoresist covered by the thin film to pattern the surface of the hydrophilic substrate having a region covered by the hydrophobic thin film and an uncovered region of the hydrophilic substrate, thereby creating a mixed wettability surface on the hydrophilic substrate representing the micro-model.

Description

Background Art

[0001] Multiphase fluid flow is a mixed flow of fluids with different phases. Thus, a fluid comprising water, oil, and gas is a fluid with different phases. A fundamental understanding of complex fluid transport and multiphase flow in porous media is crucial for many industrial processes including engineering applications across different disciplines such as biomedical engineering, environmental engineering, and petroleum engineering.

[0002] Micromodels are an emerging platform for representing porous media with complex structural shapes and pore sizes. Paper models have attracted extensive industrial attention due to their great scalability and ability to observe the fundamental mechanisms of fluid recovery at the pore scale and simulate actual rock pore networks with high spatial resolution.

[0003] Imbibition is the process of absorbing a wetting phase into a porous rock. Wettability is the tendency of a solid to come into contact with one liquid or gas (called the wetting phase) rather than another. The wetting phase tends to spread on the surface of the solid, and the porous solid tends to imbibite the wetting phase. The wettability of a rock depends on which phase imbibs more. The non-wetting phase is displaced by the wetting phase. Rocks can be water-wet, oil-wet, or intermediate-wet. Mixed rock wettability is a surface wettability in which the rock surface has both water-wet and oil-wet properties. This can be due to a variety of factors, including the chemical composition of the rock, the presence of natural organic compounds, and the interaction of fluids with the rock surface.

[0004] Drainage is the process of forcing a non-wetting phase (such as oil) into porous rock. In the presence of a solid surface, fluid-fluid displacement is affected by the wettability of the porous medium and the solid surface, drainage or imbibition, and multiphase flow. Displacement efficiency is the fraction of oil recovered from the area swept by the displacing fluid (such as water).

[0005] Although recent advances have focused on coatings of micromodels, current technology enables the construction of either water-wet or oil-wet micromodels. Surface treatments that alter surface wettability use different materials and techniques. However, a method for achieving representative mixed wetting conditions, where selective hydrophilic and hydrophobic regions are precisely controlled, is still missing from current knowledge.

[0006] Therefore, there is a need for a method for fabricating micromodels having mixed-wetness surfaces representative of oil and gas reservoirs. Summary of the invention

[0007] In general, in one aspect, the present invention relates to a method for making a micromodel having a mixed wettability surface representing an oil and gas reservoir. The method includes: coating the top surface of a hydrophilic substrate with a photoresist; covering the top of the photoresist with a photomask, wherein the photomask includes a pattern transparent to UV light; exposing the covered top of the photoresist to UV light, which changes the chemical properties of the region of the photoresist corresponding to the pattern of the photomask; removing the photomask; removing the region of the photoresist corresponding to the pattern of the photomask based on the chemical properties of the region; depositing a hydrophobic film on top of the hydrophilic substrate; and removing the remaining photoresist covered by the film, so that the surface of the hydrophilic substrate is patterned, with regions covered by the hydrophobic film and uncovered regions of the hydrophilic substrate, thereby generating a mixed wettability surface representing a micromodel on the hydrophilic substrate.

[0008] In general, in one aspect, the present invention relates to a method for making a micromodel having a mixed wettability surface representing an oil and gas reservoir. The method includes: coating the top surface of a hydrophobic substrate with a photoresist; covering the top of the photoresist with a photomask, wherein the photomask includes a pattern transparent to UV light; exposing the covered top of the photoresist to UV light, wherein the UV light changes the chemical properties of the photoresist in an area corresponding to the pattern of the photomask; removing the photomask; removing an area of ​​the photoresist based on its chemical properties, wherein the removed area corresponds to the pattern of the photomask; depositing a hydrophilic film on top of the substrate; and removing the remaining photoresist covered by the hydrophilic film, so that the surface of the hydrophobic substrate is patterned, with areas covered by the hydrophilic film and uncovered areas of the hydrophobic substrate, thereby generating a mixed wettability surface representing a micromodel on the hydrophobic substrate.

[0009] In general, in one aspect, the present invention relates to a method for making a micromodel having a mixed wettability surface representing an oil and gas reservoir. The method includes: depositing a hydrophobic film on the top surface of a hydrophilic substrate; coating the top of the hydrophobic film with a photoresist; covering the top of the photoresist with a photomask, wherein the photomask includes a pattern transparent to UV light; exposing the covered top of the photoresist to UV light, wherein the UV light changes the chemical properties of the photoresist in the area corresponding to the pattern of the photomask; removing the photomask; removing the area of ​​the photoresist based on the chemical properties of the area, wherein the removed area corresponds to the pattern of the photomask; removing the hydrophobic film in the area not covered by the photoresist; and removing the remaining photoresist so that the surface of the substrate is patterned with areas covered by the hydrophobic film and uncovered areas of the hydrophilic substrate, thereby generating a mixed wettability surface representing the micromodel on the substrate.

[0010] In general, in one aspect, the present invention relates to a method for making a micromodel having a mixed wettability surface representing an oil and gas reservoir. The method includes: depositing a hydrophilic film on the top surface of a hydrophobic substrate; coating the top of the film with a photoresist; covering the top of the photoresist with a photomask, wherein the photomask includes a pattern transparent to UV light; exposing the covered top of the photoresist to UV light, wherein the UV light changes the chemical properties of the photoresist in the area corresponding to the pattern of the photomask; removing the photomask; removing the area of ​​the photoresist based on the chemical properties of the area, wherein the removed area corresponds to the pattern of the photomask; removing the film in the area not covered by the photoresist; and removing the remaining photoresist so that the surface of the substrate is patterned with areas covered by the hydrophilic film and uncovered areas of the hydrophobic substrate, thereby generating a mixed wettability surface representing the micromodel on the substrate.

[0011] Other aspects and advantages of the present invention will become apparent from the following description and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A flow chart of a first method for fabricating a micromodel having a mixed-wetness surface representative of a hydrocarbon reservoir is shown in accordance with one or more embodiments.

[0013] Figure 2 A substrate processed by a first method according to one or more embodiments is shown.

[0014] Figure 3 A flow chart of a second method for fabricating a micromodel having a mixed-wetness surface representative of a hydrocarbon reservoir is shown in accordance with one or more embodiments.

[0015] Figure 4 A substrate processed by the second method according to one or more embodiments is shown.

[0016] Figure 5 A schematic diagram of a substrate having a mixed wettability surface is shown according to one or more embodiments.

[0017] Figure 6 Water droplets are shown on a substrate surface according to one or more embodiments.

[0018] Figure 7 A surface having mixed wettability according to one or more embodiments is shown. Figure 5 The base of.

[0019] Fig. 8A A silicon-based substrate having a selective hybrid wettability surface is shown in accordance with one or more embodiments.

[0020] Figure 8B A mixed wettability surface is shown in accordance with one or more embodiments. DETAILED DESCRIPTION

[0021] In the following detailed description of the embodiments of the present disclosure, many specific details are set forth to provide a more thorough understanding of the present disclosure. However, it is obvious to those skilled in the art that the present disclosure can be practiced without these specific details. In other cases, well-known features are not described in detail to avoid unnecessarily complicating the description.

[0022] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in the application). Unless explicitly disclosed, such as using the terms "before," "after," "single," and other such terms, the use of ordinal numbers does not imply or create any particular order of elements, nor does it limit any element to only a single element. Instead, the use of ordinal numbers is to distinguish between elements. As an example, a first element is different from a second element, and a first element may contain more than one element and be ranked after (or before) a second element in the ordering of elements.

[0023] In one aspect, an embodiment disclosed in the present specification relates to a method for manufacturing a micromodel having a mixed wettability surface representing an oil and gas reservoir, the method comprising the following steps: coating the top surface of a hydrophilic substrate with a photoresist; covering the top of the photoresist with a photomask, wherein the photomask includes a pattern that is transparent to UV light; exposing the covered top of the photoresist to UV light, which changes the chemical properties of the photoresist in an area corresponding to the pattern of the photomask; removing the photomask; removing an area of ​​the photoresist based on the chemical properties of the area, wherein the removed area corresponds to the pattern of the photomask; depositing a hydrophobic film on top of the substrate; and removing the remaining photoresist covered by the film, so that the surface of the substrate forms a pattern having areas covered by the hydrophobic film and uncovered areas of the hydrophilic substrate, thereby forming a mixed wettability surface representing the micromodel on the substrate.

[0024] The method for making micromodels with mixed wettability surfaces enables the creation of selective hydrophilic and hydrophobic regions that are precisely distributed on the surface of a substrate. Making micromodels with selective wettability surfaces helps simulate actual mixed wettability rocks that represent oil and gas reservoirs.

[0025] The silicon-based surface of the micromodel has good compatibility for oil and gas applications, including high temperature and pressure and affinity for organic uses of crude oil and solvents. The area of ​​the micromodel substrate coated with perfluorodecyltrichlorosilane (FDTS) causes the local wetting state of silicon to shift in the hydrophobic direction, while the wettability of the uncoated silicon substrate remains unchanged. The proposed fabrication method produces a microfluidic device, also known as a "reservoir-on-a-Chip", which has controlled mixed wetting properties.

[0026] Embodiments of the present disclosure may provide at least one of the following advantages. The method is capable of producing a hydrophobic surface in a selected area by changing the hydrophilic surface properties of the substrate, and vice versa. In this way, selective hydrophilic and hydrophobic regions can be contained and precisely controlled at the micrometer and nanometer scales. By adjusting the wetting state of the substrate to simulate any desired mixed wetting characteristics of the system, a pore-scale platform can be formed, providing great opportunities for basic fluid flow analysis and fluid-surface interaction research. In addition, the method can be integrated and implemented in many application areas, such as but not limited to microfluidics and electronics. Both the first method and the second method for manufacturing a mixed wettability surface are applicable to non-patterned and patterned surfaces.

[0027] The method consists of two main steps: photolithography and thin film deposition. Photolithography is the process of producing geometric patterns from a photomask to a photoresist on the surface of a substrate. Thin film deposition, on the other hand, places very thin layers of material on the surface of a substrate. This step precisely determines the target wettability of the surface. Depending on the wettability state of the original surface of the substrate, the deposition of hydrophobic or hydrophilic material is performed to create a contrast in wettability.

[0028] Figure 1 A flow chart 100 showing method steps for producing a mixed wettability surface according to a first photolithography method is shown. The method comprises the following steps.

[0029] In step 102, the top surface of the hydrophilic substrate is coated with a photoresist. In some embodiments, the substrate is coated with the photoresist by spin coating.

[0030] Spin coating is performed by a spin coater or simply a spinner. Spin coating deposits a uniform thin film onto a flat substrate. A relatively small amount of fluid photoresist is applied to the center of the substrate while the substrate is spinning at a low speed or not spinning at all. The substrate is then rotated at speeds up to 10,000 rpm to spread the fluid photoresist through centrifugal force. The substrate is rotated while the fluid photoresist spins away from the edge of the substrate until the desired thickness of the photoresist is obtained. The thickness of the photoresist depends on the viscosity of the photoresist and the speed of rotation. The faster the rotation, the thinner the photoresist. The fluid photoresist is then dried.

[0031] In step 104, the top of the photoresist is covered with a photomask, wherein the photomask includes a pattern that is transparent to UV light. The pattern of the photomask includes holes or transparent bodies in the photomask that allow UV light to shine through the photomask. The resolution of the pattern can be as fine as 1 μm. The pattern can include squares, circles, triangles, or any other geometric shapes.

[0032] There are two types of photoresists: positive photoresists and negative photoresists. In the case of positive photoresists, the areas exposed to UV light are degraded by the UV light. The areas covered by the photomask and shielded from the UV light remain undegraded. In the case of negative photoresists, the areas of the photoresist exposed to UV light are enhanced, and the areas covered by the photomask and shielded from the UV light remain weaker. The first and second methods are applicable to both positive and negative photoresists.

[0033] In step 106, the covered top portion of the photoresist is exposed to UV light, which changes the chemistry of the photoresist in areas corresponding to the pattern of the photomask. In some embodiments, the UV light has a wavelength between 10 nm and 400 nm.

[0034] In step 108, the photomask is removed. The photomask can be removed separately or together with the photoresist (as described in the next step).

[0035] In step 110, the area is removed based on the chemical properties of the area of ​​the photoresist, wherein the removed area corresponds to the pattern of the photomask. In some embodiments, the chemical properties include degradation or hardness. The area removed in the photoresist also corresponds to the pattern of the area exposed to UV light. The type of photoresist determines whether to remove the area of ​​the photoresist exposed to UV light or the area of ​​the photoresist not exposed to UV light.

[0036] Areas of the photoresist are removed by the photoresist developer. In the case of positive photoresists, the areas of the photoresist that are degraded by UV light become soluble in the photoresist developer, while the non-degraded areas of the photoresist remain insoluble in the photoresist developer. In the case of negative photoresists, the areas of the photoresist that are enhanced by UV light become insoluble in the photoresist developer, while the weak areas of the photoresist are dissolved by the photoresist developer.

[0037] In step 112, a hydrophobic film is deposited on top of the substrate. The film can be deposited by atomic layer deposition (ALD), molecular layer deposition (MVD), pulsed laser deposition (PLD), physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering or evaporation. ALD is a thin film deposition technique based on the continuous use of gas phase chemical processes. ALD uses two chemical substances called precursors, which react with the surface of the substrate one at a time. The film is slowly deposited by repeated exposure to a separate precursor. MVD is a gas phase reaction between a surface reactive chemical substance and a suitable receiving surface of the substrate. The film is deposited on the substrate surface to obtain the desired wetting properties. PLD focuses a high power pulsed laser beam in a vacuum chamber to hit a target of a thin film material. The thin film material vaporizes from the target in the form of a plasma plume and is deposited as a thin film on the substrate facing the target. PVD is a vacuum deposition method in which the film changes from a condensed phase to a gas phase and then returns to a condensed phase. CVD is a vacuum deposition method in which a substrate is exposed to a volatile precursor that reacts and / or decomposes on the surface of the substrate to produce the desired thin film deposition. The main requirement for achieving this process is the correct selection of precursors that provide the desired wettability and the ability to deposit stable thin films.

[0038] In some embodiments, the film includes perfluorodecyltrichlorosilane (FDTS) or any other hydrophobic material. The surface of the substrate is completely covered by the film. The thickness of the film is a few nanometers.

[0039] Thin films including hydrophobic FDTS using MVD produce surface wetting properties that modify many materials used in fabricating micropatterns, such as silicon, glass, polydimethylsiloxane, and polymer-based photoresists.

[0040] In case of a hydrophilic substrate, the deposited film should be hydrophobic. On the other hand, if the substrate is hydrophobic, the film should be hydrophilic. In this way, a mixed wetting surface is produced.

[0041] In step 114, the remaining photoresist covered by the film is removed. A solvent is used to remove the remaining photoresist. In some embodiments, the solvent is N-methylpyrrolidone (NMP). The remaining photoresist is removed to restore the original substrate surface. A mixed wettability surface is generated, in which the area covered by FDTS is hydrophobic, while the area without FDTS deposition is hydrophilic.

[0042] After removing the remaining photoresist, the surface of the substrate is patterned with areas covered by the hydrophobic film and uncovered areas where the hydrophilic substrate is not covered. In other words, the surface of the substrate is a mixture of hydrophobic areas and hydrophilic areas. Since the hydrophobic areas and the hydrophilic areas have different wettabilities, the surface of the substrate is a mixed wettability surface. Substrates with mixed wettability surfaces are used as micromodels, for example, to represent reservoir rocks.

[0043] Figure 2 A schematic diagram 200 depicting a substrate 220 processed by a first method for making a mixed wettability surface is shown.

[0044] In a first step 202, the surface of a silicon-based hydrophilic substrate 220 (e.g., a wafer) is dehydrated and baked at a temperature of 150°C (300°F) to remove any moisture on the surface of the substrate 220. This step is optional. Subsequently, an adhesion promoter is applied to the surface to promote adhesion of the photoresist 222 to the surface of the substrate 220 (see step 204). Prior to applying the adhesion promoter, the surface of the substrate 220 may be activated to improve the adhesion of the surface of the substrate 220.

[0045] The surface of substrate 220 can be activated by plasma cleaning, which removes impurities and contaminants from the surface of substrate 220 by high-energy plasma generated by gas. The gas can be argon, oxygen, or a mixture of air, hydrogen and nitrogen. Plasma is generated by ionizing low-pressure gas using high-frequency voltage. In some embodiments, oxygen plasma can be used for surface activation.

[0046] In the next step 204 , the processed top surface of the substrate 220 is coated with a photoresist 222 .

[0047] In step 206, the top of the photoresist 222 is covered with a photomask 224, wherein the photomask 224 includes a pattern that is transparent to UV light. The photomask 224 is called a selective wettability control mask and is aligned on top of the photoresist 222. In some embodiments, the pattern of the photomask 224 includes holes that allow UV light to shine through the photomask 224.

[0048] In step 208 , the covered top portion of the photoresist 222 is exposed to UV light, which changes the chemistry of the areas of the photoresist 222 that correspond to the pattern of the photomask 224 .

[0049] In step 210, the coated substrate 220 is baked at a high temperature (eg, 110° C.) to cure the photoresist 222. After baking, the photomask 224 is removed.

[0050] In step 212, areas of photoresist 222 are removed based on their chemistry, where the removed areas correspond to the pattern of photomask 224. A solvent called a photoresist 222 developer is applied to the surface of substrate 220 to remove areas of photoresist 222 that also correspond to the pattern of areas exposed to UV light.

[0051] In step 214 , a hydrophobic film 226 is deposited on top of the substrate 220 .

[0052] In step 216 , the remaining photoresist covered by the film 226 is removed, so that the surface of the substrate 220 is patterned with areas covered by the hydrophobic film 226 and uncovered areas of the hydrophilic substrate 220 , thereby generating a mixed wettability surface on the substrate 220 representing the micromodel.

[0053] Figure 3 A flow chart 300 showing method steps for producing a mixed-wetting surface according to a second method is shown. The second method comprises the following steps.

[0054] In step 302, a hydrophobic film is deposited on the top surface of a hydrophilic substrate.

[0055] In step 304, the top of the hydrophobic film is coated with photoresist.

[0056] In step 306, the top of the photoresist is covered with a photomask, wherein the photomask includes a pattern that is transparent to UV light.

[0057] In step 308, the covered top portion of the photoresist is exposed to UV light, which changes the chemistry of the photoresist in areas corresponding to the pattern of the photomask.

[0058] In step 310, the photomask is removed.

[0059] In step 312, regions of the photoresist are removed based on their chemistry, wherein the removed regions correspond to the pattern of the photomask.

[0060] In step 314, the hydrophobic film in the areas not covered by the photoresist is removed.

[0061] In step 316, the remaining photoresist is removed, so that the surface of the substrate forms a pattern having areas covered by the hydrophobic film and uncovered areas of the hydrophilic substrate, thereby generating a mixed wettability surface on the substrate representing the micromodel.

[0062] Figure 4 A substrate 220 is shown that has been processed by a second method for making a mixed-wetting surface.

[0063] The first step 402 is an initial surface cleaning and treatment step. This step is optional and can be applied to the surface of any silicon-based substrate 220. In some embodiments, a piranha solution or a solution containing hydrofluoric acid is applied to the surface of the substrate 220.

[0064] In step 404 , a hydrophobic film 226 is deposited on the top surface of the hydrophilic substrate 220 .

[0065] In step 406, the top of the hydrophobic film 226 is coated with a photoresist 222. The substrate 220 is then soft-baked on a hot plate to remove any volatile solvents in the photoresist 222.

[0066] In step 408 , the top of the photoresist 222 is covered with a photomask 224 , wherein the photomask 224 includes a pattern that is transparent to UV light. The photomask 224 , also referred to as a selective wettability control mask, is aligned on top of the photoresist 222 .

[0067] In step 410, the covered top portion of the photoresist 222 is exposed to UV light, which changes the chemistry of the photoresist 222 in areas corresponding to the pattern of the photomask 224. The photomask 224 is then removed.

[0068] In step 412, areas of photoresist 222 are removed based on their chemistry, wherein the removed areas correspond to the pattern of photomask 224. Step 412 is referred to as a development step.

[0069] In step 414, the hydrophobic film 226 in the area not covered by the photoresist 222 is removed. In some embodiments, the area of ​​the film 226 not covered by the photoresist 222 is removed from the substrate 220 by etching. Therefore, step 414 is referred to as an etching step. For etching, a strong acid or a mordant is used to cut into the uncovered area of ​​the film 226.

[0070] In step 416, the remaining photoresist 222 is removed, so that the surface of the substrate 220 is patterned with areas covered by the hydrophobic film 226 and uncovered areas of the hydrophilic substrate 220, thereby generating a mixed wettability surface representing the micromodel on the substrate 220. A solvent is used to remove the remaining photoresist 222. In some embodiments, the photoresist 222 includes NMP. A mixed wettability surface is generated in which the areas covered by the FDTS are hydrophobic, while the areas without the FDTS are hydrophilic.

[0071] Figure 5 A schematic diagram of a substrate 220 having a mixed wettability surface manufactured by a wettability control mask according to a first method is shown. The substrate includes a hydrophilic region 504 and a hydrophobic region 506. The hydrophobic region 506 forms a pattern of squares. According to step 214 of the first method, the squares are coated with FDTS. The size of the squares is shown in an enlarged portion 508 of the surface of the substrate 220.

[0072] As an example for illustration purposes only, the lateral length of each square is 3000 μm. The distance from one square to the adjacent square is 9000 μm. The hydrophobicity can be tested as described in step 212 of the first method.

[0073] Figure 6 A water droplet 602 is shown on the surface of substrate 220. The contact angle θ of the water droplet is C The contact angle θ is the angle between the liquid-air interface of the water droplet and the (solid) surface of the substrate 220. C The wettability of a water droplet on the surface of a substrate is described by Young's equation:

[0074] γ SG =γ SL +γ LG cos(θ C )

[0075] where γ SG is the surface free energy of the substrate, γ SL is the interfacial tension between the water droplet and the substrate, γ LG is the surface tension of the water droplet.

[0076] Equilibrium contact angle θ G It reflects the relative strength of the molecular interaction between the water droplet and the substrate.

[0077] Figure 7 Shows Figure 5220 with deionized water droplets on the surface of the substrate. Water droplets 510 and 512 are arranged at positions 506 and 504, respectively, spanning the area completely coated with the hydrophobic material FDTS. Water droplet 516 is arranged directly on the untreated surface 502 of the substrate.

[0078] The contact angle of water drop 510 is 117°. The contact angle of water drop 512 is 110°. The contact angle of water drop 516 is 119.5°. This illustrates the non-selectivity in the surface fully coated with the hydrophobic material, so that all contact angles show high values ​​at different locations.

[0079] Fig. 8A A silicon-based substrate 802 having a selective hybrid wettability surface fabricated by the first method is shown. The selective hybrid wettability surface is fabricated after removing the photoresist in step 214 of the first method. The remaining photoresist and FDTS are stripped from the substrate using a solvent including NMP to restore the original surface of the substrate.

[0080] exist Fig. 8A 8 shows an enlarged view of three water droplets 804, 806, 808 arranged on a surface 802. The first water droplet is arranged on an area not covered by FDTS and thus has a contact angle of 50°. The second and third water droplets are arranged on an area covered by FDTS and thus have contact angles of 108.5° and 112.5°, respectively.

[0081] The contact angles of three water droplets confirm the selective mixed wettability of the surface fabricated according to the first method. The area covered by FDTS is hydrophobic, while the area not covered by FDTS is hydrophilic, thus establishing a large contrast in the water and air contact angles.

[0082] Figure 8B A first surface 802 is shown with four water drops 804, 806, 808, 810 and a second surface 812 with two water drops 814, 816. On the first surface 802, the first water drop 804 has a small contact angle, wherein the second, third, and fourth water drops 806, 808, 810 have large contact angles. On the second surface 812, the first water drop 814 has a small contact angle, wherein the second water drop 816 has a large contact angle.

[0083] Although only a few exemplary embodiments are described in detail above, it will be readily appreciated by those skilled in the art that many modifications may be made in the exemplary embodiments without substantially departing from the present invention. Therefore, all such modifications are intended to be included within the scope of the present disclosure as defined by the appended claims. In the claims, a means-plus-function clause is intended to cover structures described in the present disclosure as performing the enumerated functions, which not only cover structural equivalents, but also cover equivalent structures. Therefore, although nails and screws may not be structural equivalents because nails use cylindrical surfaces to fix wooden parts together, while screws use helical surfaces, nails and screws may be equivalent structures in the context of fastening wooden parts. It is the applicant's express intention not to invoke Section 112(f) of the United States Patent Act to impose any limitations on any claim in this specification, except for those where the claims explicitly use the phrase "device for..." together with associated functions.

Claims

1. A method for making a micromodel having a mixed wettability surface representative of an oil and gas reservoir, comprising the following steps: Coat the top surface of the hydrophilic substrate with photoresist, covering the top of the photoresist with a photomask, wherein the photomask includes a pattern that is transparent to UV light, exposing the covered top portion of the photoresist to UV light which changes the chemistry of the photoresist in areas corresponding to the pattern of the photomask, removing the photomask, removing areas of the photoresist corresponding to the pattern of the photomask based on the chemical properties of the areas, depositing a hydrophobic film on top of the hydrophilic substrate, and The remaining photoresist covered by the film is removed, so that the surface of the hydrophilic substrate is patterned with areas covered by the hydrophobic film and uncovered areas of the hydrophilic substrate, thereby generating a mixed wettability surface representing the micromodel on the hydrophilic substrate.

2. The method according to claim 1, wherein: The region of the photoresist is removed by applying a photoresist developer to the photoresist.

3. The method according to claim 2, wherein: The photoresist is positive-working, and areas of the photoresist exposed to UV light are degraded and become soluble in the photoresist developer, while areas of the photoresist covered by the photomask and shielded from the UV light remain undegraded and insoluble in the photoresist developer.

4. The method according to claim 2, wherein: The photoresist is negative-working, and areas of the photoresist exposed to UV light are enhanced by the UV light and become insoluble in the photoresist developer, while areas not exposed to the UV light remain weak and insoluble in the photoresist developer.

5. The method according to claim 1, wherein: The photoresist is applied by spin coating.

6. The method according to claim 1, wherein: The thin film is deposited by atomic layer deposition (ALD), molecular layer deposition (MVD), pulsed laser deposition (PLD), physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering or evaporation.

7. The method according to claim 1, wherein: The film includes perfluorodecyltrichlorosilane (FDTS).

8. The method according to claim 1, wherein: The remaining photoresist is removed by N-methylpyrrolidone (NMP).

9. The method according to claim 1, wherein: Prior to coating the surface of the substrate with photoresist, the hydrophilic substrate was baked at a temperature of 150°C (300°F).

10. The method according to claim 9, wherein: After baking the substrate, an adhesion promoter is applied to the surface of the substrate.

11. The method of claim 1, wherein the surface of the substrate is activated by plasma cleaning before coating the surface of the substrate with a photoresist.

12. The method according to claim 11, wherein: The plasma cleaning is performed by oxygen plasma.

13. The method according to claim 1, wherein: After exposing the covered top portion of the photoresist to UV light, the coated substrate was baked at a temperature of 110°C.

14. A method for making a micromodel having a mixed wettability surface representative of an oil and gas reservoir, the method comprising the steps of: Coating the top surface of the hydrophobic substrate with a photoresist, covering the top of the photoresist with a photomask, wherein the photomask includes a pattern that is transparent to UV light, exposing the covered top portion of the photoresist to UV light which changes the chemistry of the photoresist in areas corresponding to the pattern of the photomask, removing the photomask, removing the areas of the photoresist based on the chemical properties of the areas, wherein the removed areas correspond to the pattern of the photomask, depositing a hydrophilic film on top of the substrate, and The remaining photoresist covered by the hydrophilic film is removed, so that the surface of the hydrophobic substrate is patterned with areas covered by the hydrophilic film and uncovered areas of the hydrophobic substrate, thereby generating a mixed wettability surface representing the micromodel on the hydrophobic substrate.

15. A method for making a micromodel having a mixed wettability surface representative of an oil and gas reservoir, the method comprising the steps of: Depositing a hydrophobic film on the top surface of a hydrophilic substrate, coating the top of the hydrophobic film with photoresist, covering the top of the photoresist with a photomask, wherein the photomask includes a pattern that is transparent to UV light, exposing the covered top portion of the photoresist to UV light which changes the chemistry of the photoresist in areas corresponding to the pattern of the photomask, removing the photomask, removing regions of the photoresist based on the chemical properties of the regions, wherein the removed regions correspond to the pattern of the photomask, removing the hydrophobic film in areas not covered by the photoresist, and The remaining photoresist is removed, so that the surface of the substrate is patterned with a pattern of areas covered by the hydrophobic film and uncovered areas of the hydrophilic substrate, thereby generating a mixed wettability surface on the substrate representing the micromodel.

16. A method for making a micromodel having a mixed wettability surface representative of an oil and gas reservoir, the method comprising the steps of: Depositing a hydrophilic film on the top surface of a hydrophobic substrate, Coat the top of the film with photoresist, covering the top of the photoresist with a photomask, wherein the photomask includes a pattern that is transparent to UV light, exposing the covered top portion of the photoresist to UV light which changes the chemistry of the photoresist in areas corresponding to the pattern of the photomask, removing the photomask, removing regions of the photoresist based on the chemical properties of the regions, wherein the removed regions correspond to the pattern of the photomask, removing the film in areas not covered by the photoresist, and The remaining photoresist is removed, so that the surface of the substrate is patterned with a pattern of areas covered by the hydrophilic film and uncovered areas of the hydrophobic substrate, thereby generating a mixed wettability surface on the substrate representing the micromodel.

17. The method according to claim 16, wherein: The thin film is removed by etching the surface of the substrate.

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