Polyimide hydrophobic drag reducing microstructured surface

Abstract

This invention discloses a hydrophobic and drag-reducing microstructured surface of polyimide. The polyimide surface has a periodically arranged array of grooved microstructures, with groove width, depth, and spacing all ranging from 250 to 350 μm. The static contact angle between the grooved microstructured surface and water is 110°–130°, an increase of 40°–60° compared to a smooth polyimide plane. This surface achieves enhanced hydrophobicity through the microstructure roughness effect, requiring no chemical modification or coating, exhibiting good structural stability, and is suitable for applications such as underwater vehicles and marine equipment.

Description

Technical Field

[0001] This invention relates to the field of functional surface technology, specifically to a polyimide hydrophobic drag-reducing microstructure surface, which is particularly suitable for drag reduction applications in underwater environments. Background Technology

[0002] Polyimide (PI) is a high-performance polymer material with excellent thermal stability, mechanical strength, chemical resistance, and lightweight properties, making it promising for applications in aerospace, marine engineering, and flexible electronics. However, the smooth surface of polyimide results in a static contact angle with water that is typically only 65°-75°, making it hydrophilic. This leads to significant frictional resistance in underwater environments, limiting its application in marine equipment and underwater vehicles.

[0003] In existing technologies, methods to improve the hydrophobic properties of polyimide surfaces mainly include chemical modification and coating techniques. Chemical modification methods reduce surface energy by introducing fluorine or silicon elements, but they suffer from problems such as complex processes, poor durability, and easy peeling. Coating techniques achieve hydrophobic effects by applying a hydrophobic coating to the polyimide surface, but the bonding strength between the coating and the substrate is limited, and it is prone to failure under water erosion and long-term immersion.

[0004] Surface microstructure technology offers a new approach to improving the hydrophobic properties of material surfaces. By constructing arrays of microstructures with specific morphologies on the material surface, and utilizing the roughness effect and trapped air effect, hydrophobic or even superhydrophobic effects can be achieved without altering the material's inherent properties. However, existing research on microstructured hydrophobic surfaces mainly focuses on materials such as metals and silicon, with limited research on microstructured hydrophobic surfaces of polyimide materials. Furthermore, existing microstructures are mostly submicron or nanoscale, making them difficult and costly to fabricate, and their aspect ratios are limited, making it difficult to maintain stable hydrophobic properties and drag reduction effects in high-speed underwater flow environments.

[0005] Therefore, there is an urgent need for a microstructured surface based on polyimide bulk that has stable hydrophobic and drag-reducing properties, which can balance hydrophobicity, structural stability and processing feasibility. Summary of the Invention

[0006] The purpose of this invention is to find a way to achieve hydrophobicity and drag reduction on the surface of polyimide without altering the inherent properties of the polyimide material or introducing additional coatings, through surface microstructure design.

[0007] A hydrophobic and drag-reducing microstructured surface of polyimide, wherein the polyimide surface has a periodically arranged array of groove microstructures, the width of the grooves being 250-350 μm, the depth being 250-350 μm, and the spacing being 250-350 μm, the static contact angle between the groove microstructured surface and water being 110°-130°, which is 40°-60° higher than the static contact angle of a smooth polyimide plane, and the polyimide hydrophobic and drag-reducing microstructured surface is suitable for underwater environments.

[0008] Preferably, the width, depth, and spacing of the trenches are all 280-320 μm.

[0009] Preferably, the static contact angle between the surface of the groove microstructure and water is 118°-125°.

[0010] Preferably, the static contact angle of the smooth polyimide plane is 65°-75°, and the contact angle of the grooved microstructure surface is increased by 45°-55°.

[0011] Preferably, the direction of the trench is parallel to the direction of water flow or forms an angle of 0°-15°.

[0012] Preferably, the polyimide is a thermosetting polyimide.

[0013] Preferably, the polyimide hydrophobic drag-reducing microstructure surface is used on the surface of underwater vehicles, marine equipment, or microfluidic chips.

[0014] The present invention has the following beneficial effects: Significantly improved hydrophobic properties: Through the design of groove microstructures of specific sizes, the static contact angle of the polyimide surface is increased from about 70° on a smooth plane to 110°-130°, an increase of 40°-60°, realizing the transformation from hydrophilic to hydrophobic.

[0015] Good structural stability: The microstructure is integrally molded with the polyimide substrate, eliminating the risk of coating peeling off, and maintaining stable performance under long-term underwater immersion and high-speed scouring environments.

[0016] Excellent corrosion resistance: Polyimide materials themselves have excellent chemical corrosion resistance and are suitable for harsh environments such as seawater.

[0017] Drag reduction potential: The trench microstructure can change the boundary layer flow state and has the potential for underwater drag reduction applications.

[0018] High feasibility of processing: The feature size of the groove is on the order of hundreds of micrometers, which can be achieved through ultra-precision processing technology. The processing difficulty is lower than that of nanoscale microstructures. Attached Figure Description

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments: Figure 1 3D schematic diagram of the surface of polyimide trench microstructure; Figure 2 SEM images and outlines of the trench microstructure array; Figure 3 Photograph of contact angle measurement on a smooth polyimide plane (70°); Figure 4 Photograph of the surface contact angle of the groove microstructure (121°). Detailed Implementation

[0020] The present invention will be further explained below with reference to specific implementation schemes, but it is not limited to the present invention. The structures, proportions, sizes, etc. shown in the accompanying drawings are only used to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are for illustrative purposes only and do not constitute any limitation on the scope of protection of this invention.

[0022] Example: Preparation and characterization of polyimide trench microstructure surface An ultra-precision flying cut method was used to fabricate a grooved microstructure array on the surface of a thermosetting polyimide film. Using a single-point diamond tool, the cutting depth was controlled at 300 μm, and the feed rate at 500 mm / min, resulting in a periodic groove array with a width of 300 μm, a depth of 300 μm, and a spacing of 300 μm. The groove direction was parallel to the long side of the sample.

[0023] The static contact angles of smooth polyimide planes and grooved microstructure surfaces were measured using a contact angle meter. The static contact angle of the smooth polyimide plane was 70°, and that of the grooved microstructure surface was 121°, representing an increase of 51° in the contact angle, thus achieving a transition from hydrophilic to hydrophobic.

[0024] Matters not covered in this invention are common knowledge.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A polyimide hydrophobic drag-reducing microstructure surface, characterized in that, The polyimide surface has a periodically arranged array of groove microstructures. The width of the grooves is 250-350 μm, the depth is 250-350 μm, and the spacing is 250-350 μm. The static contact angle between the groove microstructure surface and water is 110°-130°, which is 40°-60° higher than the static contact angle of a smooth polyimide plane. The polyimide hydrophobic drag-reducing microstructure surface is suitable for underwater environments.

2. The polyimide hydrophobic drag-reducing microstructure surface according to claim 1, characterized in that, The width, depth, and spacing of the trenches are all 280-320 μm.

3. The polyimide hydrophobic drag-reducing microstructure surface according to claim 1, characterized in that, The static contact angle between the surface of the grooved microstructure and water is 118°-125°.

4. The polyimide hydrophobic drag-reducing microstructure surface according to claim 1, characterized in that, The static contact angle of the smooth polyimide plane is 65°-75°, and the contact angle of the grooved microstructure surface is increased by 45°-55°.

5. The polyimide hydrophobic drag-reducing microstructure surface according to claim 1, characterized in that, The polyimide is a thermosetting polyimide.

6. The polyimide hydrophobic drag-reducing microstructure surface according to claim 1, characterized in that, Used on the surface of underwater vehicles, marine equipment, or microfluidic chips.

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