Unique Structure and Mechanical Property of Dabryanus Scale

The structure and mechanical property of Dabryanus scale were investigated. Environmental Scanning Electron Microscopy (ESEM) and Transmission Electron Microscopy (TEM) were used to observe the scale structure. The scale has a discrete osseous layer which is composed of boat-like unit (due to the shape). The osseous layer is embedded into fibrillary layer, and the largest thickness ratio of osseous layer to fibrillary layer is about 7, much higher than those of other reported fish scales. Nanoindentation test was used to investigate mechanical property of the scale. Elastic modulus (Er) and hardness (H) of Dabryanus scale are much lower than those of other reported fish scales. Scale models were proposed and the principles of materials mechanics were used to analyze the mechanical properties of the Dabryanus scale. The boat-like unit in osseous layer makes the scale flexible while keeping a high thickness ratio of osseous layer to fibrillary layer, which increases the flexibility and protection capacity of the scale This study may provide new strategy for the design of flexible armor or flexible devices.