Active Metamaterial Skins for Friction Coefficient Control

Nature is ripe with biological organisms that possess unique capabilities of changing their skin for various purposes. In particular, many of these natural phenomena are derived from their unique surface topographies. Many attempts have been made to optimize artificial surfaces to increase or decrease friction depending on operational needs. This study introduces an “active skin” based on mechanical metamaterials that harvest instabilities in order to exploit unusual properties. In its pristine state, the surface properties of flat active skins are governed by its intrinsic material properties. When strained, each of the architected units undergoes out-of-plane deformations that drastically change its surface characteristics (i.e., friction). Notches are introduced at judicious locations to control the buckling orientation or each unit cell that plays an important role in the active skin’s surface friction properties. Thus, based on the idea of harvesting structural instabilities, this study introduces a reversible, reconfigurable, active skin that features programmable 3D deformations.