Table_2_Ridges and riblets: Shark skin surfaces versus biomimetic models.docx

Shark skin has been an inspiration for biomimetic materials and structures due to its role in reducing drag and enhancing thrust, properties believed to be due to the textured surface composed of ridges on the surface of individual tooth-like scales (denticles). Attempts to replicate the hydrodynamic performance of shark skin have involved manufacturing both engineered riblets and fabrics with textured surfaces. However, there are no studies that compare the surface ornamentation of shark denticles to bioinspired materials. Using three-dimensional surface profilometry we analyzed the cross-sectional profile of the surface of shark denticles at two locations on 17 species and compared these data to values obtained from engineered structures (e.g., riblets) and competition swimsuits that are often proposed as having a comparable surface texture to shark skin. Of the variables measured, crown aspect ratio (p = 0.007), ridge height, ridge spacing, ridge aspect ratio, and ridge bumpiness (all p < 0.001) differed among the three materials. Overall, engineered riblet surfaces were very different than biological shark skin. Some of the competition swimsuit materials were more shark-like, with the fabric texture having similar height variation, but with irregular ridge spacing. Cross-sectional profile, which includes pathlength and aspect ratio in addition to ridge spacing and height, is an important feature of the skin’s surface, affecting water flow over the individual denticles, and future research will address these parameters. Quantitative 3D analysis of the surface of real shark denticle ridges enables the design of more biomimetic engineered shark skin surfaces.

鲨鱼皮肤因其降低阻力并增强推力的特性，而被视为仿生材料和结构的灵感之源。这些特性被认为源于由表面类似牙齿的鳞片（齿脊）构成的纹理表面。复制鲨鱼皮肤流体动力学性能的尝试包括制造了工程肋条和具有纹理表面的织物。然而，目前尚无研究将鲨鱼齿脊的表面装饰与仿生材料进行比较。我们利用三维表面轮廓测量技术，分析了17种鲨鱼两种位置的齿脊横截面轮廓，并将这些数据与工程结构（例如肋条）以及通常被认为具有与鲨鱼皮肤相似表面纹理的竞速泳衣获得的值进行了比较。在测量的变量中，齿脊冠部比例（p = 0.007）、齿脊高度、齿脊间距、齿脊比例以及齿脊粗糙度（所有p < 0.001）在三种材料中均存在差异。总体而言，工程肋条表面与生物鲨鱼皮肤差异显著。某些竞速泳衣材料更接近鲨鱼皮肤，其织物纹理具有相似的高度变化，但齿脊间距不规则。横截面轮廓，包括路径长度和比例，以及齿脊间距和高度，是皮肤表面的一个重要特征，它影响水流对单个齿脊的流动，未来的研究将解决这些参数。对真实鲨鱼齿脊表面的定量三维分析，能够促进更加仿生的工程鲨鱼皮肤表面的设计。