Large-scale solvent-swelling-based amplification of microstructured sharkskin

Abstract

Sophisticated biomimetic microstructures/nanostructures have attracted attention worldwide, but their fabrication technique significantly restricts their application. This study uses natural sharkskin to investigate amplification (i.e., the bioscaling forming process) and thus acquire a complex microstructure that cannot be fabricated by traditional micromachining techniques. The bioscaling forming process adjusts the optimal function region of natural surfaces by utilizing the solvent-swelling effect of polydimethylsiloxane. To accurately replicate amplified sharkskin, the swelling ratio and rate in gaseous and liquid n-hexane were investigated. Epoxy resin was used to produce a positive sharkskin mold. A comparison between the microstructure of the original and amplified sharkskin shows that the swelling ratio can reach a maximum of 34% with gaseous n-hexane and 39% with liquid n-hexane. The accuracy of bioscaling forming was higher than 95%. The drag-reducing effect was also tested. When the sharkskin was amplified 1.34 times, the optimal velocity range of the drag reduction moved from 5.0 to 3.5 m s−1.

Bio‐inspired drag reduction surface from sharkskin

“…By experiments, it is clear that the sharkskin can be amplified up to 45% in the one‐time swelling process and much larger amplification can be realised by multiple amplification processes as shown in Fig. 9 [30, 35, 36]. The maximal drag reduction of amplified sharkskin was validated to be transferred to low‐speed region.…”

“…In order to extend the potential application to high fluid velocity, the sharkskin should be shrunken in large scale [35]. Chen et al developed the large-proportional shrunken bio-replication method.…”

“…Hirt and Thome explored rolling method in detail to realise large area fabrication of the riblet structure [33, 34]. Luo and Zhang exploited the microrolling method to fabricate continuous vivid sharkskin on a semi‐cured epoxy resin coating [35]. In the fabricating process, the flat polymethyl methacrylate (PMMA) plate as a negative template is heated to glass state.…”

“…SEM images of vivid sharkskin template and large proportion shrunken sharkskin are shown in Fig. 11 [35].…”

Patterning of worm‐like soft polydimethylsiloxane structures using a TiO2 nanotubular array

“…A PDMS stamp can be achieved either by masking the flat PDMS followed by etching with ultraviolet (UV) light, 12 or by molding of PDMS using textured surfaces from natural or synthetic materials. Natural materials such as plant leaves, [13][14][15] shark skin, 16 and sea urchin 17 have micropatterned surface that can be deployed for PDMS mold. Geometrically complex surfaces from nature may provide the opportunity to enhance understanding of microbial attachment on a unique topography.…”