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Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices.

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The advantages of utilizing the polymeric shape memory effect for deterministic assembly of microscale objects are explored in this letter. The assembly is performed by transfer printing, which involves a polymeric stamp with reversible adhesion as a manipulator. The dynamic rigidity control afforded by heating or cooling a shape memory polymer (SMP) stamp across its glass transition temperature allows for a dramatic increase in adhesion during pick-up. Furthermore, the shapefixing and recovery property of the SMP material enables substantial freedom in stamp design, such as more complex surface patterning and heterogeneous surface features to further reduce adhesion during release not otherwise available.[2014-0158]