Utilization of Melt Fracture Phenomenon for the Preparation of Shark Skin Structured Hydrophobic Film

With the application of biomimetic shark skin microstructures with hydrophobicity in microfluidics, sensors and self-cleaning materials, microstructure processing methods are increasing. The preparation process has higher requirements for processing cost and efficiency. In this paper, linear low-density polyethylene (LLDPE) hydrophobic films were prepared with the help of melt fracture phenomenon. The equipment is a self-made single screw extruder. By adjusting the process parameters, the biomimetic shark skin structured LLDPE films with good hydrophobic property can be obtained. The surface microstructure shape of the product is related to kinds of additive, die temperature and screw speed. When AC5 was selected as an additive, the optimal processing parameter was found to be 160 °C die temperature and 80 r/min screw speed. A contact angle of 133° was obtained in this situation. In addition, the influences of die temperature and screw speed on the size of shark skin structure were also systematically investigated in this paper. It was found that the microstructure surface with hierarchical roughness had a better hydrophobic property.

A Study to Compare the Fouling Resistance and Self-cleaning Properties of Two-patterned Surfaces with an Un-patterned Control Surface

Biofouling is an unwelcomed phenomenon where unwanted biological matter adheres to surfaces with the presence of water, resulting in alteration to the properties of the surface. This affects many industries, especially the marine industry. Multiple biofouling control studies have been conducted to minimize damage and maintenance cost of these surfaces. With rising concerns on the toxicity of current control methods towards the environment, non-toxic methods shown to be effective are surface modifications such as self-cleaning or biomimetic textured surfaces. One of the biomimetic surfaces, shark’s skin has shown anti-fouling properties due to its surface riblets with low drag properties based on studies done. However, few researches are conducted to implement these biomimetic surface topographies for real anti-fouling applications. Therefore, this project explores the possibilities in implementing biomimetic surface topographies such as shark’s skin in real life applications using computational fluid dynamics (CFD) analysis and also to manufacture these surfaces using 3D printing methods. A computer-aided design (CAD) model of shark skin and un-patterned surface topographies are used to study the behavior of fluid over these surfaces in CFD fluent in ANSYS software. The hydrodynamic variable data such as wall shear stress over the surface topography is represented in a contour and vector plot, these results are then analyzed. According to the hypotheses, the biomimetic shark skin surface topography will show higher wall shear stress, indicating anti-fouling properties. In the next part of this project is the manufacturing of these surface, the goal is to provide a cheaper alternative to current micro-structured surface production methods such as photolithography. Additive manufacturing such as fused deposition modeling (FDM) 3D printing can potentially provide a manufacturing method with a much lower cost and time needed. Thus, 3D printing of the biomimetic shark skin surface topography will be carried out in this project to determine if FDM can provide a manufacturing solution to anti-fouling micro-topography surfaces.

Preparation and Evaluation of the Curative Effect of Blue Shark (Prionace glauca) Skin Collagen Composite Gel in a Rat Oral Ulcers Model

Objective: To evaluate the curative effect of blue shark skin collagen composite gel on oral mucosal ulcer using the rat oral ulcers model stimulated by glacial acetic acid. Methods: Collagen from blue shark skin was isolated and physiochemically characterized by FTIR, SDS-PAGE and scanning electron microscopy (SEM). Seventy standard male rats were divided into seven groups. The surface and the area of the ulcer were observed and calculated daily. After 12 days of administration, rats in the model group and the control group were killed and the ulcer and surrounding tissues were cut to pieces about one mm3 size. The specimens were stained with 10% formalin solution, paraffinembedded sections, HE staining and light microscope were used to observe the histopathological changes in ulcer tissues. Results: The high-dose group had the fastest ulcer healing effects after 12 days of treatment with blue shark skin collagen composite gel. The composite gel was found to significantly accelerate the healing of oral ulcers in a dose-dependent manner. Conclusion: The blue shark skin collagen composite gel in this study may be a good biomedical material candidate for the treatment of oral ulcers in the near future. Potential of other marine fish skin collagen comples on healing oral ulcers should be also considered.

Computational analysis to enhance the compressible flow over an aerofoil surface

Purpose Since the inception of aerospace engineering, reducing drag is of eternal importance. Over the years, researchers have been trying to improve the aerodynamics of National Advisory Committee for Aeronautics (NACA) aerofoils in many ways. It is proved that smooth-surfaced NACA 0012 aerofoil produces more drag in compressible flow. Recent research on shark-skin pattern warrants a feasible solution to many fluid-engineering problems. Several attempts were made by many researchers to implement the idea of shark skin in the form of coatings, texture and more. However, those ideas are at greater risk when it comes to wing maintenance. The purpose of this paper is to implement a relatively larger biomimetic pattern which would make way for easy maintenance of patterned wings with improved performance. Design/methodology/approach In this paper, two biomimetic aerofoils are designed by optimizing the surface pattern of shark skin and are tested at different angles of attack in the computational flow domain. Findings The results of the biomimetic aerofoils prove that viscous and total drag can be reduced up to 33.08% and 3.68%, respectively, at high subsonic speed when validated against a NACA 0012 aerofoil. With the ample effectiveness of patched shark-skin pattern, biomimetic aerofoil generates as high as 10.42% lift than NACA 0012. Originality/value In this study, a feasible shark-skin pattern is constructed for NACA 0012 in a transonic flow regime. Computational results achieved using the theoretical model agree with experimental data.