Abstract
Nano-long chains were grafted over the replicated micro-grooves of shark skin in a novel attempt to replicate bio-synthetic drag reduction structure with high precision through synthetic bio-replication. Pre-treated shark skin was used as casting template to prepare a flexible female die of silicone rubber by soft die formation. A waterborne epoxy resin was then used to graft long-chains of drag reduction agent and prepare a synthetic drag reduction shark skin with nano-long chain drag reduction interface and lifelike micro-grooves. Replication precision analysis shows that this technology could replicate the complicated three-dimensional morphology of a biological drag reduction surface with high precision. Drag reduction experiments show that the material had an excellent synthetic drag reduction effect, with a maximal drag reduction rate of up to 24.6% over the velocities tested.
Highlights
Nano-long chains were grafted over the replicated micro-grooves of shark skin in a novel attempt to replicate bio-synthetic drag reduction structure with high precision through synthetic bio-replication
Replication precision analysis shows that this technology could replicate the complicated three-dimensional morphology of a biological drag reduction surface with high precision
Drag reduction experiments show that the material had an excellent synthetic drag reduction effect, with a maximal drag reduction rate of up to 24.6% over the velocities tested
Summary
Shark skin (150 mm×150 mm) of Isurus oxyrinchus (body side), which is a typically fast-swimming shark, was taken as the template for bio-replication [15]. It could be applied to manufacture a flexible female die [16]. A waterborne epoxy resin, composed of water-based epoxy resin emulsion (AB-EP-44) and waterborne epoxy curing agent (AB-HGF), was used for forming the replicate material base. Polyacrylamide (PAM), a water-soluble linear polymer drag reduction agent with a molecular weight of over 3 million and a chain segment length of 0.25 nm [17], was used for forming the nano-long chain drag reduction interface. A graft copolymer of waterborne epoxy resin and PAM was used as the substrate of synthetic drag reduction shark skin. Dibutyl phthalate (DBP), a universal plasticizer [18], was used for improving the ductility and flexibility of substrate
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