Emergence of instability-driven domains in soft stratified materials

Nature frequently employs the buckling phenomenon to facilitate the formation of complicated patterns across length-scales.Current knowledge,however,is limited to a small set of buckling-induced microstructure transformations in soft composites;and the pattern formation phenomenon remains largely unknown for a vast pool of material morphologies.Here,we investigate the unexplored rich domain of soft heterogeneous composites.We experimentally observe the formation of instability-driven domains in stratified composites with a non-dilute stiff phase.We illustrate that the discovered domain patterns are energetically favorable over wrinkling.Moreover,we introduce a closed-form analytical expression allowing us to predict the evolution of the patterns in the post-buckling regime.Finally,we show that various patterns can be pre-designed via altering material compositions.These findings can help advance our understanding of the mechanisms governing pattern formations in soft biological tissues,and potentially enable the platform for mechanical metamaterials.