Preparation method of PDMS (Polydimethylsiloxane) surface with directional droplet transport characteristic

Abstract

The invention relates to the technical field of functional materials and liquid control, in particular to a preparation method of a PDMS (Polydimethylsiloxane) surface with a directional droplet transport characteristic. The preparation method comprises the following steps: S1, forming a groove-shaped micro-nano structure on the surface of a silicon wafer by using a metal catalytic etching method; s2, taking a silicon wafer with the groove-shaped micro-nano structure as a template, uniformly mixing a PDMS matrix and a curing agent according to a mass ratio of 10: 1 to form a prepolymer, pouring the prepolymer on the surface of the silicon wafer with the groove-shaped micro-nano structure, discharging bubbles in the prepolymer, heating and curing, and separating the prepolymer from the silicon wafer template to obtain a PDMS sample with the surface with the groove-shaped micro-nano structure; s3, immersing the PDMS surface with the groove-shaped structure into absolute ethyl alcohol containing a fluorinated modifier for soaking treatment, and drying; and S4, spin-coating dimethyl silicone oil on the surface of the PDMS sample which is subjected to surface fluorination treatment and has the groove-shaped micro-nano structure to form a silicone oil layer, thereby obtaining the PDMS surface with the liquid drop directional transportation characteristic.

Description

Technical Field

[0001] The invention relates to the technical field of functional materials and liquid control, and in particular to a method for preparing a PDMS surface with droplet directional transport characteristics. Background Art

[0002] Directed droplet transport refers to the phenomenon that droplets move, spread or penetrate in a specific direction by using external forces or the physical and chemical properties of a specific surface. Directed droplet transport has broad application prospects in the fields of microfluidics, liquid collection, liquid separation, self-cleaning and anti-icing.

[0003] In order to realize the characteristics of directional transport of droplets on the surface, there are two common methods at this stage: one is to control the movement of droplets through external fields, where the external fields mainly include electric fields, magnetic fields, optical fields and temperature fields; the other is to destroy the symmetry of droplets by preparing specific surface structures, so as to cause the droplets to spread or transport in a specific direction. At present, surfaces that use specific surface structures to achieve directional transport characteristics of droplets usually need to be prepared by micro-nano processing methods such as lithography, 3D printing, physical and chemical deposition, and self-growth. Therefore, the preparation process is relatively complicated and the preparation cost is high, which limits the actual production and application of droplet directional transport surfaces. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for preparing a PDMS surface having droplet directional transport properties, the preparation method comprising the following steps:

[0006] S1. Forming a groove-shaped micro-nano structure on the surface of a silicon wafer by using a metal catalytic etching method;

[0007] S2, using a silicon wafer with a grooved micro-nano structure as a template, uniformly mixing a PDMS matrix and a curing agent at a mass ratio of 10:1 to form a prepolymer, pouring the prepolymer on the surface of the silicon wafer with a grooved micro-nano structure, expelling bubbles in the prepolymer, and separating it from the silicon wafer template after heating and curing to obtain a PDMS sample with a grooved micro-nano structure on the surface;

[0008] S3, immersing the PDMS surface with the grooved structure in anhydrous ethanol containing a fluorinated modifier for immersion treatment and drying;

[0009] S4. Spin-coat dimethyl silicone oil on the surface of the PDMS sample with a grooved micro-nano structure that has been surface fluorinated to form a silicone oil layer to obtain a PDMS surface with droplet directional transport properties.

[0010] Furthermore, the specific operation steps of step S1 are: cleaning the silicon wafer with acetone and deionized water in turn and drying it with nitrogen or compressed air; then immersing the cleaned silicon wafer in a metal catalytic etching solution for etching, and cleaning the etched silicon wafer with deionized water; immersing the silicon wafer cleaned with deionized water in a cleaning solution to remove metal particles deposited on the surface of the silicon wafer during the etching process, and cleaning the silicon wafer after the metal is removed with deionized water and drying it with nitrogen or compressed air to obtain a silicon wafer with a grooved micro-nano structure on the surface.

[0011] Furthermore, the metal catalytic etching solution includes catalytic metal ions, an oxidant, hydrofluoric acid and deionized water, the etching temperature is 10 to 80° C., and the etching time is 1 to 60 minutes.

[0012] Furthermore, the catalytic metal ion is Ag + 、Au + , Pt + 、Ni 2+ , Fe 2+ and Cu 2+ The concentration of the oxidant is 1-500 mmol / L; the oxidant comprises one or more of H2O2, HNO3 and KMnO4, with a concentration range of 0.1-5 mol / L; the concentration of the hydrofluoric acid is 1-10 mol / L.

[0013] Furthermore, the cleaning liquid is one or more of HNO3, NH4OH, HCl and H2O2 solutions, the cleaning temperature is 10-80°C, and the cleaning time is 1-60 minutes; when nitric acid solution is used as the cleaning liquid, the concentration range of the nitric acid solution is 20-80wt%.

[0014] Furthermore, the mass ratio of the PDMS matrix and the curing agent used for uniformly mixing to form the prepolymer is 10:1; the heating curing temperature is 20 to 100° C., and the curing time is 0.5 to 24 hours.

[0015] Furthermore, the fluorinated modifier is one or more of dodecyltrimethoxysilane, hexadecyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane and tridecafluorooctyltriethoxysilane, and the mass fraction of the fluorinated modifier is 0.5-5wt%.

[0016] Furthermore, the temperature range of the immersion treatment is 10 to 50° C., and the immersion time is 1 to 24 hours.

[0017] Furthermore, the viscosity of the dimethyl silicone oil is in the range of 50-500 mm 2 / s, the rotation speed during spin coating is 500-3000r / min, and the spin coating time is 10-60s.

[0018] A PDMS surface with droplet directional transport characteristics is prepared by the above-mentioned method for preparing a PDMS surface with droplet directional transport characteristics.

[0019] Beneficial effects of the present invention:

[0020] 1. The PDMS surface covered with a silicone oil layer and having a grooved micro-nano structure prepared by the preparation method provided by the present invention can limit the transport of droplets on the surface to a specific direction parallel to the extension direction of the grooves, and thus has good droplet directional transport characteristics.

[0021] 2. The preparation of the PDMS surface with droplet directional transport characteristics provided by the present invention is mainly achieved through a template method. Compared with the conventional technical route of preparing specific micro-nano structures on the surface using micro-nano processing technologies such as lithography, 3D printing, physical and chemical deposition, and self-growth, the preparation method proposed by the present invention has a simple process and strong operability. It can promote the widespread application of transparent surfaces for droplet directional transport and has good application prospects in the fields of microfluidics, liquid collection, liquid separation, self-cleaning, and anti-icing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a schematic diagram of the preparation process of a surface with droplet directional transport characteristics proposed by the present invention.

[0024] Figure 2 It is a groove-shaped micro-nano structure prepared on a silicon wafer by a metal catalytic etching method in Example 1 of the present invention.

[0025] Figure 3 is the contact angle of the deionized water droplet on the surface of the PMDS sample covered with a silicone oil layer and having a grooved micro-nano structure on the surface in Example 1 of the present invention. The contact angle is 100° and the volume of the deionized water droplet is 5 μL.

[0026] Figure 4 1 is a diagram showing the process of a deionized water droplet moving on the PDMS surface parallel to the groove extension direction in Example 1 of the present invention. The upper and lower figures correspond to the position of the deionized water droplet on the PDMS surface at t=0s and t=2s, respectively. At this time, the inclination angle of the PDMS sample surface is 15°, and the volume of the deionized water droplet is 5 μL.

[0027] Figure 5This is a process diagram of the movement of the deionized water droplet on the PDMS surface perpendicular to the groove extension direction in Example 1 of the present invention. The upper and lower figures correspond to the position of the deionized water droplet on the PDMS surface at t=0s and t=5s, respectively. At this time, the inclination angle of the PDMS sample surface is 15°, and the volume of the deionized water droplet is 5μL. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] For the purpose of this specification and the appended claims, unless otherwise stated, all numbers expressing amounts, percentages or ratios and other numerical values ​​used in this specification and the appended claims are understood to be modified in all cases by the term "about". In addition, all ranges disclosed herein are inclusive and independently combinable.

[0030] Embodiment 1:

[0031] Step 1: Use metal catalytic etching method to form groove-shaped micro-nano structures on the surface of silicon wafer

[0032] Take a silicon wafer with a size of 20 mm × 20 mm and immerse it in acetone and deionized water in turn for cleaning and blow dry with nitrogen gas;

[0033] The cleaned silicon wafer is immersed in a metal catalytic etching solution for etching to form a groove-shaped micro-nano structure on the surface of the silicon wafer. The concentrations of the components in the metal catalytic etching solution are 100mmol / L Cu(NO3)2, 5mol / L HF, 1.2mol / LH2O2, respectively. The etching temperature is 25℃ and the etching time is 4min.

[0034] The etched silicon wafer was immersed in deionized water for cleaning and dried with nitrogen gas;

[0035] The etched and cleaned silicon wafer was immersed in a 69wt% HNO3 solution for cleaning to remove the metal Cu particles deposited on the surface of the silicon wafer. The cleaning temperature was 25°C and the cleaning time was 30min. The silicon wafer cleaned with the HNO3 solution was immersed in deionized water for cleaning and dried with nitrogen to obtain a silicon wafer with a grooved micro-nano structure on the surface.

[0036] Step 2: Using a silicon wafer with a grooved micro-nano structure as a template, a PDMS sample with a grooved micro-nano structure on the surface is prepared by a template method.

[0037] The PDMS matrix and the curing agent with a mass ratio of 10:1 are uniformly mixed to form a prepolymer, and the prepolymer is poured on a silicon wafer with a grooved micro-nano structure on the surface, and the silicon wafer is placed in a negative pressure environment and left to stand for 1 hour to remove bubbles in the prepolymer on the surface of the silicon wafer;

[0038] The silicon wafer with the prepolymer on the surface was placed in an oven and heated to cure the prepolymer to form PDMS. The curing temperature was 50°C and the curing time was 2h.

[0039] The PDMS formed after curing is separated from the silicon wafer template to obtain a PDMS sample with a grooved micro-nano structure on the surface.

[0040] Step 3: Surface fluorination treatment of the prepared PDMS sample with grooved micro-nanostructure on the surface

[0041] The PDMS sample with grooved micro-nanostructure on the surface prepared in step 2 is immersed in an anhydrous ethanol solution containing 1 wt % of tridecafluorooctyltriethoxysilane for immersion treatment at a temperature of 25° C. for 4 h;

[0042] The PDMS sample with a grooved micro-nano structure on the surface after immersion treatment was dried at a temperature of 80° C. for 4 h.

[0043] Step 4: Spin coating to form a silicone oil layer on the surface of the PDMS sample with grooved micro-nano structure after surface fluorination treatment.

[0044] The viscosity is 100mm 2 / s dimethyl silicone oil was poured onto the surface of the PDMS sample with grooved micro-nano structure after surface fluorination treatment, and spin coating was performed at a speed of 2000r / min and a spin coating time of 20s to obtain a PDMS surface covered with dimethyl silicone oil and with grooved micro-nano structure, that is, a PDMS surface with droplet directional transport characteristics.

[0045] The contact angle and sliding angle tests were conducted on the PDMS surface with droplet directional transport characteristics. The results showed that the contact angle of deionized water on the PDMS surface in Example 1 was 100°; the sliding angle of the deionized water droplet on the PDMS surface parallel to the groove extension direction was 5°, and the sliding angle on the PDMS surface perpendicular to the groove extension direction was 18°. The sliding angle test results show that the deionized water droplet is easy to slide on the PDMS surface parallel to the groove extension direction, but not easy to slide in the perpendicular groove extension direction, indicating that the PDMS surface has good droplet directional transport characteristics.

[0046] Embodiment 2:

[0047] Step 1: Use metal catalytic etching method to form groove-shaped micro-nano structures on the surface of silicon wafer

[0048] Take a silicon wafer with a size of 20 mm × 20 mm and immerse it in acetone and deionized water in turn for cleaning and blow dry with nitrogen gas;

[0049] The cleaned silicon wafer is immersed in a metal catalytic etching solution for etching to form a groove-shaped micro-nano structure on the surface of the silicon wafer. The concentrations of the components in the metal catalytic etching solution are 100mmol / L Cu(NO3)2, 5.5mol / L HF, and 1.5mol / LH2O2, respectively. The etching temperature is 30℃ and the etching time is 5min.

[0050] The etched silicon wafer was immersed in deionized water for cleaning and dried with nitrogen gas;

[0051] The etched and cleaned silicon wafer was immersed in a 69wt% HNO3 solution for cleaning to remove the metal Cu particles deposited on the surface of the silicon wafer. The cleaning temperature was 25°C and the cleaning time was 45min. The silicon wafer cleaned with the HNO3 solution was immersed in deionized water for cleaning and dried with nitrogen to obtain a silicon wafer with a grooved micro-nano structure on the surface.

[0052] Step 2: Using a silicon wafer with a grooved micro-nano structure as a template, a PDMS sample with a grooved micro-nano structure on the surface is prepared by a template method.

[0053] The PDMS matrix and the curing agent with a mass ratio of 10:1 are uniformly mixed to form a prepolymer, and the prepolymer is poured on a silicon wafer with a grooved micro-nano structure on the surface, and the silicon wafer is placed in a negative pressure environment and left to stand for 1 hour to remove bubbles in the prepolymer on the surface of the silicon wafer;

[0054] The silicon wafer with the prepolymer on the surface was placed in an oven and heated to solidify the mixed solution to form PDMS. The curing temperature was 60°C and the curing time was 1.5 h.

[0055] The PDMS formed after curing is separated from the silicon wafer template to obtain a PDMS sample with a grooved micro-nano structure on the surface.

[0056] Step 3: Surface fluorination treatment of the prepared PDMS sample with grooved micro-nanostructure on the surface

[0057] The PDMS sample with grooved micro-nanostructure on the surface prepared in step 2 is immersed in an anhydrous ethanol solution containing 1wt% dodecyltrimethoxysilane for immersion treatment at a temperature of 25°C for 3h;

[0058] The PDMS sample with a grooved micro-nano structure on the surface after the immersion treatment was dried at a temperature of 90° C. for 4 h.

[0059] Step 4: Spin coating to form a silicone oil layer on the surface of the PDMS sample with grooved micro-nano structure after surface fluorination treatment.

[0060] The viscosity is 500mm 2 / s dimethyl silicone oil was poured into the surface of the PDMS sample with grooved micro-nano structure after surface fluorination treatment, and spin coating was performed at a speed of 3000r / min and a spin coating time of 15s to obtain a PDMS surface covered with dimethyl silicone oil and having a grooved micro-nano structure, that is, a PDMS surface with droplet directional transport characteristics.

[0061] The contact angle and sliding angle tests were conducted on the PDMS surface with droplet directional transport characteristics. The results showed that the contact angle of deionized water on the PDMS surface in Example 2 was 107°; the sliding angle of the deionized water droplet on the PDMS surface parallel to the groove extension direction was 7°, and the sliding angle on the PDMS surface perpendicular to the groove structure was 20°. The sliding angle test results show that the deionized water droplet is easy to slide on the PDMS surface parallel to the groove extension direction, but not easy to slide in the direction perpendicular to the groove extension direction, indicating that the PDMS surface has good droplet directional transport characteristics.

[0062] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0063] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a PDMS surface having droplet directional transport properties, characterized in that: The preparation method comprises the following steps: S1. Forming a groove-shaped micro-nano structure on the surface of a silicon wafer by using a metal catalytic etching method; S2, using a silicon wafer with a grooved micro-nano structure as a template, uniformly mixing a PDMS matrix and a curing agent at a mass ratio of 10:1 to form a prepolymer, pouring the prepolymer on the surface of the silicon wafer with a grooved micro-nano structure, expelling bubbles in the prepolymer, and separating it from the silicon wafer template after heating and curing to obtain a PDMS sample with a grooved micro-nano structure on the surface; S3, immersing the PDMS surface with the grooved structure in anhydrous ethanol containing a fluorinated modifier for immersion treatment and drying; S4. Spin-coat dimethyl silicone oil on the surface of the PDMS sample with a grooved micro-nano structure that has been surface fluorinated to form a silicone oil layer to obtain a PDMS surface with droplet directional transport properties.

2. The method for preparing a PDMS surface having droplet directional transport properties according to claim 1, characterized in that: The specific operation steps of step S1 are: cleaning the silicon wafer with acetone and deionized water in turn and drying it with nitrogen or compressed air; then immersing the cleaned silicon wafer in a metal catalytic etching solution for etching, and cleaning the etched silicon wafer with deionized water; immersing the silicon wafer cleaned with deionized water in a cleaning solution to remove metal particles deposited on the surface of the silicon wafer during the etching process, and cleaning the silicon wafer after the metal is removed with deionized water and drying it with nitrogen or compressed air to obtain a silicon wafer with a grooved micro-nano structure on the surface.

3. The method for preparing a PDMS surface having droplet directional transport properties according to claim 2, characterized in that: The metal catalytic etching solution comprises catalytic metal ions, an oxidant, hydrofluoric acid and deionized water, the etching temperature is 10-80° C., and the etching time is 1-60 minutes.

4. The method for preparing a PDMS surface having droplet directional transport properties according to claim 3, characterized in that: The catalytic metal ion is Ag + 、Au + , Pt + 、Ni 2+ , Fe 2+ and Cu 2+ The concentration of the oxidant is 1-500 mmol / L; the oxidant comprises one or more of H2O2, HNO3 and KMnO4, with a concentration range of 0.1-5 mol / L; the concentration of the hydrofluoric acid is 1-10 mol / L.

5. The method for preparing a PDMS surface having droplet directional transport properties according to claim 2, characterized in that: The cleaning liquid is one or more of HNO3, NH4OH, HCl and H2O2 solutions, the cleaning temperature is 10-80°C, and the cleaning time is 1-60 minutes; when nitric acid solution is used as the cleaning liquid, the concentration range of the nitric acid solution is 20-80wt%.

6. The method for preparing a PDMS surface having droplet directional transport properties according to claim 1, characterized in that: The mass ratio of the PDMS matrix and the curing agent used for uniformly mixing to form the prepolymer in step S2 is 10:1; the heating curing temperature is 20 to 100° C., and the curing time is 0.5 to 24 hours.

7. The method for preparing a PDMS surface having droplet directional transport properties according to claim 1, characterized in that: The fluorinated modifier in step S3 is one or more of dodecyltrimethoxysilane, hexadecyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane and tridecafluorooctyltriethoxysilane, and the mass fraction of the fluorinated modifier is 0.5-5wt%.

8. The method for preparing a PDMS surface having droplet directional transport properties according to claim 1, characterized in that: The temperature range of the soaking treatment in step S3 is 10 to 50° C., and the soaking time is 1 to 24 hours.

9. The method for preparing a PDMS surface having droplet directional transport properties according to claim 1, characterized in that: The viscosity of the dimethyl silicone oil in step S4 is in the range of 50-500 mm 2 / s, the rotation speed during spin coating is 500-3000r / min, and the spin coating time is 10-60s.

10. A PDMS surface with droplet directional transport properties prepared by the method for preparing a PDMS surface with droplet directional transport properties according to any one of claims 1 to 9.

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