(323i) Reconfigurable Macroporous Photonic Crystals Enabled By Novel Stimuli-Responsive Shape Memory Polymers
Smart shape memory polymers (SMPs) can memorize and recover their permanent shape in response to an external stimulus, such as heat, light, and solvent. They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices (e.g., surgical stents and sutures) and implants for minimally invasive surgery to aerospace morphing structures and self-healing materials. However, most of the existing SMPs are thermoresponsive and their performance is hindered by slow response speed, heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable like temperature, pressure-responsive SMPs are largely unexplored. Here, by integrating scientific principles drawn from two disparate fields that do not typically intersect - the fast-growing photonic crystal and SMP technologies, we report a new type of SMP that enables unusual "cold" programming and instantaneous shape recovery triggered by applying a contact pressure at ambient conditions. These stimuli-responsive materials differ greatly from existing SMPs as they enable orders of magnitude faster response, striking chromogenic effects, and room-temperature operations for the entire shape memory cycle, promising for applications ranging from chromogenic pressure and chemical sensors to novel biometric and anti-counterfeiting materials. Moreover, this interdisciplinary integration enables fabrication of reconfigurable photonic crystals and simultaneously provides a simple and sensitive optical technique for investigating the intriguing shape memory effects at nanoscale.