Formation of micro/nano-scale wrinkling patterns atop shape memory polymers

Wrinkling patterns in shape memory polymer (SMP) sputter deposited with a thin layer (10 s nm in thickness) of gold atop are systematically investigated under various conditions. Depending on the surface condition, heating temperature and pre-straining, different patterns of micro/nano-scaled wrinkles are produced. Although elastic buckling of the gold layer is the mechanism behind all types of wrinkles, the shape memory effect (SME) and thermal expansion mismatch (TEM) are the driving force for different patterns after heating to different temperatures, i.e. the evolution of wrinkle pattern is due to the SME after heating to low temperatures and the TEM after heating to high temperatures. The flexibility and convenience in using SMP to achieve different wrinkling patterns is demonstrated.