Control of Cytocompatible Metallic and Polymeric Wrinkle Morphologies Using Programming via Printing (PvP)

Mechanical instability-driven wrinkling of a thin rigid film on a compliant substrate, such as a shape-memory polymer (SMP), offers spatiotemporal control of surface topography and morphology. Current strategies for creating wrinkles on SMPs often rely on mechanical actuation achieved via costly or complicated uniaxial or multiaxial loading rigs. There is a need for an accessible and easily democratizable strategy that can produce both simple aligned wrinkles and complex two-dimensional (2D) postbuckling patterns. Using a hobbyist three-dimensional (3D) printer, here we employed a recently developed single-step SMP fabrication approach, programming via printing (PvP), to prepare preprogrammed shape-memory substrates capable of uniaxial or biaxial contraction of varying magnitudes, with the strain controlled by the nozzle temperature and number of orthogonal layers within the substrate. Samples without an orthogonal layer (all filaments are parallel) produced a maximum uniaxial contraction along the same axis as the extruded filament (up to 40%) and underwent Poisson expansion along the perpendicular direction (up to 15%). The substrates were coated with either gold or polystyrene, and shape-memory-driven change was triggered to cause mechanical instability-driven wrinkling of the thin film. To characterize the relationship between orthogonal layers and wrinkle morphology, wrinkles were imaged at the microscopic level using atomic force microscopy (AFM). The transition from unidirectional to bidirectional contractile strain generated by the orthogonal layers was observed to induce a transition from simple aligned wrinkles to complex 2D postbuckling patterns. C3H10T1/2 cells showed high viability (>90%) irrespective of wrinkle morphology 24 h post seeding. Collectively, the results demonstrate a convenient fabrication strategy for producing both simple aligned wrinkles and complex 2D postbuckling patterns, including cytocompatible wrinkles suitable for cell studies.