Method for preparing microgroove array surface with nearly cylindrical surface based on air molding method

Abstract

The present invention provides a method for preparing a microgroove array surface with a nearly cylindrical surface based on an air molding method, and relates to the technical field of functional surface preparation. The method includes the following steps: (1) preparing a microgroove array surface, uniformly spreading a layer of a liquid polymer film to be formed on the auxiliary plate, and placing a spacer block in an empty position on the microgroove array surface; (2) placing the auxiliary plate spread with the liquid polymer film on the spacer block on the microgroove array surface, maintaining this state, and feeding the auxiliary plate into a vacuum drying oven; and (3), setting a pressure in the vacuum drying oven according to a designed pressure, heating and solidifying the liquid polymer film, and separating the microgroove array surface to obtain the microgroove array surface with the nearly cylindrical surface.

Claims

1. An air molding method based on pre-spreading of an auxiliary plate for preparing a microgroove array surface with a nearly cylindrical surface, comprising the following steps: step 1: preparing a microgroove array surface; uniformly spreading a layer of a liquid polymer film to be molded on the auxiliary plate; and placing a spacer block at an empty position of the microgroove array surface; step 2: placing the auxiliary plate spread with the liquid polymer film on the spacer block on the microgroove array surface, and feeding the auxiliary plate into a vacuum drying oven while maintaining this state; step 3: setting a pressure in the vacuum drying oven according to a designed pressure value, heating and solidifying the liquid polymer film, and separating the liquid polymer film from the surface of the auxiliary plate to achieve the preparation of the microgroove array surface with the nearly cylindrical surface; in the step 1 of the method, the microgroove array surface is prepared by a conventional micro-processing method such as a laser direct writing processing method, a laser spot being used has a diameter of 5 μm to 100 μm, an overlap rate of the laser spot during scanning falls within 30% to 90%, a groove zone to be processed is subjected to a surface scanning 5 times to 20 times, and the prepared microgroove has a depth greater than a width of the microgroove, and wherein in the step 1, placing the spacer block at the empty position of the microgroove array surface is: preparing three spacer blocks with thicknesses less than a thickness of the liquid polymer film by 10-50 μm, and lengths and widths of the spacer blocks ranging from 1×1 mm to 5×5 mm, and placing the three spacer blocks in empty positions near edges of the microgroove array surface, the three spacer blocks being placed scatteredly, and connecting lines between the spacer blocks forming an acute triangle.

2. The air molding method based on the pre-spreading of the auxiliary plate for preparing the microgroove array surface with the nearly cylindrical surface according to claim 1, wherein in the step 1, uniformly spreading the layer of the liquid polymer film to be molded on the auxiliary plate is: dripping a liquid polymer material of polydimethylsiloxane on the auxiliary plate, and freely spreading the liquid polymer material to a required thickness for 10 s to 300 s to form the liquid polymer film with a thickness of 50-1,500 μm, and a spreading area of the liquid polymer film being capable of completely covering the microgroove array surface.

3. The air molding method based on the pre-spreading of the auxiliary plate for preparing the microgroove array surface with a nearly cylindrical surface according to claim 1, wherein in the step 2, placing the auxiliary plate spread with the liquid polymer film on the spacer block on the microgroove array surface, and feeding the auxiliary plate into the vacuum drying oven while maintaining this state is: placing the auxiliary plate spread with the liquid polymer film on the spacer block on the microgroove array surface, making the liquid polymer come into contact with the microgroove array surface to achieve liquid sealing to an air in the microgroove, keeping the microgroove array surface horizontal in subsequent operations to limit a flow of the liquid polymer film, keeping the liquid polymer film and the microgroove array surface in full contact and at a horizontal state, and feeding the liquid polymer film and the microgroove array surface into the vacuum drying oven for being ready to a treatment.

4. The air molding method based on pre-spreading of an auxiliary plate for preparing a microgroove array surface with a nearly cylindrical surface according to claim 1, wherein in the step 3, setting the pressure in the vacuum drying oven according to the designed pressure value, heating and solidifying the liquid polymer material, and separating the liquid polymer film from the surface of the auxiliary plate to achieve the preparation of the microgroove array surface with the nearly cylindrical surface is: calculating the pressure P=P.sub.0−σ/r of the vacuum drying oven according to a designed curvature radius r of the microgroove with the nearly cylindrical surface, wherein P.sub.0 is an atmospheric pressure and σ is a surface tension of the liquid formed polymer, vacuumizing the vacuum drying oven to the calculated pressure P; adjusting a temperature to 60° C. and keeping the temperature for 2 hours to solidify the formed liquid polymer film; and performing natural cooling after solidification, and separating the prepared solidified film from a microgroove template and the auxiliary plate to obtain the microgroove array surface with the nearly cylindrical surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a principle of air escape from a microgroove caused by spreading of a formed polymer;

(2) FIG. 2 is an implementation flow of a method for preparing a microgroove array surface with a nearly cylindrical surface based on an air molding method; and

(3) FIG. 3 is a placement manner of spacer blocks on a microgroove surface.

(4) 1—microgroove array surface, 2—microgroove, 3—formed polymer droplet, 4—auxiliary plate, 5—liquid polymer film, 6—formed polymer liquid between auxiliary plate and microgroove array surface, 7—formed polymer liquid subjected to vacuumizing, 8—microgroove array surface with a nearly cylindrical surface, 9—spacer block, and 10—acute triangle formed among spacer blocks.

DESCRIPTION OF THE EMBODIMENTS

(5) The following describes implementation details and working conditions of a specific technology provided by the present invention with reference to FIG. 2 and FIG. 3.

(6) An air molding method based on pre-spreading of an auxiliary plate for preparing a microgroove array surface with a nearly cylindrical surface is shown in FIG. 2, and includes four steps: preparing a microgroove array surface, pre-spreading a liquid formed polymer on the auxiliary plate, making the spread liquid formed polymer come into contact with the microgroove array surface to achieve liquid seal, and performing vacuum forming, solidifying and separating operations on the formed polymer to obtain the microgroove array surface with the nearly cylindrical surface based on the air molding method.

(7) Firstly, the microgroove array surface 1 is prepared by a certain method, the surface may be prepared through conventional micro-processing methods such as a laser direct writing processing method and a photoetching processing method, and a prepared microgroove 2 has a depth greater than a width of the microgroove 2. When laser direct writing processing method is used, a laser beam directly acts on a smooth surface, such that a material of a local zone of the smooth surface may be removed, and a specific groove may be obtained by repeatedly removing the material and controlling the laser beam to scan a specific path. When the photoetching processing method is used, firstly, a mask plate is customized, and then a certain smooth base material is coated with photoresist, and then a pattern of the mask plate is projected onto the photoresist through a photoetching exposure system, such that performance of the photoresist changes, and the microgroove array surface 1 is obtained through subsequent technologies such as development, hard baking, corrosion and photoresist removal.

(8) Secondly, a liquid polymer film 5 is pre-spread on the auxiliary plate 4. The auxiliary plate 4 is coated with a layer of the liquid formed polymer film 5 with a thickness of 50-1,500 μm. In the case of a liquid polymer, the micro-liquid polymer film 5 (with a volume of 50 μL<V<1,500 μL) is poured onto the auxiliary plate 4, and the liquid polymer film is spread with a required thickness (50-1,500 μm) through a spin coater or using the gravity.

(9) Thirdly, the spread liquid polymer film 5 is made to come into contact with the microgroove array surface 1 to form the liquid seal. The microgroove array surface 1 is placed horizontally. Spacer blocks 9 are placed in empty positions of edges of the microgroove array surface 1. As shown in FIG. 3, it is ensured that lines between the spacer blocks form an acute triangle 10 among the spacer blocks, and it is ensured that the spacer block 9 has a thickness less than a thickness of the spread liquid polymer film 5 by 10-50 μm. Then the spread liquid polymer film 5 is in contact with the microgroove array surface 1. At this time, the liquid formed polymer forms a specific shape under the action of the surface tension and air pressure, that is, formed polymer liquid 6 between the auxiliary plate and the microgroove array surface is formed, such that residual air inside the microgroove is sealed by the polymer.

(10) Fourthly, vacuum forming, solidifying and separating operations are performed on the formed polymer, so as to prepare the microstructure through the air molding method. The microgroove array surface 1 in the previous step is kept being horizontally placed and fed into a vacuum drying oven together with the formed polymer liquid 6 between the auxiliary plate and the microgroove array surface and the auxiliary plate 4. The pressure P=P.sub.0−σ/r of the vacuum drying oven is calculated according to a designed curvature radius r of the microgroove with the nearly cylindrical surface, P.sub.0 is an atmospheric pressure, and σ is a surface tension of the formed polymer. The vacuum drying oven is vacuumized to the calculated pressure P, so as to convert the formed polymer liquid into formed polymer liquid 7 subjected to vacuumizing. The formed polymer liquid 7 subjected to vacuumizing is heated and solidified and separated from the auxiliary plate 4 and the microgroove array surface 1. According to the law of the interface pressure and the interface curvature radius in the Laplace equation, the microgroove structure obtained is a microgroove structure with a nearly cylindrical surface, that is, a microgroove array surface with a nearly cylindrical surface 8 is formed.

(11) Embodiment 1 (PDMS is selected as a liquid polymer film 5, a smooth Si surface is selected as an auxiliary plate 4, and a silicon wafer fragment is selected as a spacer block)

(12) An ordinary microgroove array surface 1 is prepared through laser direct writing processing, in which a laser spot used has a diameter of 20 μm, an overlap rate of the laser spot during scanning is 50%, that is, a distance between two consecutive spots is 10 μm, and a microgroove zone to be processed is subjected to surface scanning 10 times. A 1060 aluminum plate is selected as a substrate surface, and the microgroove has a width of 50 μm, a depth of 100 μm, and a groove length of 2 μm after processing. 300 μL of PDMS (purchased from Dow Corning Company, USA, trade name Sylgard 184A) is dropwise added on the auxiliary smooth Si surface. After the PDMS is spread freely for 3 minutes, a smooth and flat silicon wafer coated with the liquid PDMS film can be obtained. The prepared microgroove 1060 aluminum plate is placed horizontally, and three silicon wafer fragments with a thickness of 200 μm are placed at edges of the microgroove 1060 aluminum plate as spacer blocks. Then the silicon wafers spread with the liquid PDMS film are placed on the spacer blocks, such that the residual air inside the microgroove is sealed by the PDMS film. The microgroove 1060 aluminum plate in a horizontal state is, together with the auxiliary smooth Si surface and the liquid PDMS, are fed into a vacuum drying oven. A curvature radius is designed as 50 μm. The vacuum pressure is calculated as 100,925 Pa. Vacuumizing is performed according to the pressure. Heating is performed to 60° C. Heat preservation is kept for 2 hours. Then natural cooling is performed, and the polymer film is separated from the auxiliary plate and the microgroove array surface to obtain a microgroove array surface with a nearly cylindrical surface with a width of 50 μm and a depth of 50 μm.