Optimal design of micro-topography on natural leaf surface

Optimal design of flexible micro-topography is of fundamental importance for numerous applications, such as in membranes, sensors, and MEMS. Different from rigid micro-topography, surfaces displaying flexible micro-topography are able to absorb external energy by transforming their shape, which makes them suitable to be used under complex operating conditions. In this study, we find that the micro-structures occurring on biological natural surfaces all have a common structural feature, namely, an ellipsoid shape. The flexible sleek micro-structures without right angles are able to decrease the stress concentration and deformation in the loading process, which may prevent the nano-structures from being damaged on the upper surfaces. To clearly understand the performance of these micro-topographies, a series model is established by force analysis. The model uncovers the design principles that lead to the mechanical enhancement of natural composites for expanding the application of flexible micro-/nano-structured membranes.