Shape-memory effect for self-healing and biodegradable photonic systems

Photonic systems with the capability to respond to different stimuli are more and more desirable for achieving multifunctionality and higher levels of performance. They demand materials with responsivity that may eventually be used for integrating sensing and actuating functions, a feature highly pursued in technological applications. A notable property which is being gradually incorporated in this kind of multifunctional materials is the shape memory effect (SME). In this work, a material system consisting of a two-dimensional photonic crystal (PC) imprinted in the surface of a shape memory polymer (SMP) is reported. It integrates several interesting features such as elasticity, thermoresponsivity and shape memory. The referred PC is composed of a hexagonal lattice of nanobowls, transferred to the SMP surface using replica molding. Good quality and large extensions of PC were achieved. Differential scanning calorimetry studies confirmed a melting transition responsible for the SME in these materials. From the structural point of view, their surfaces were characterized by atomic force and scanning electron microscopies. From the optical point of view, the characterization of the first order Bragg diffraction angle was carried out. A full programmable character of the structures, derived from the SME, was demonstrated. The reported material system presents some interesting additional features. In particular, the SMP selected for replicating the PC belongs to the family of polydiolcitrates, which are known to be biocompatible and biodegradable elastomers. The PC described herein is thus attractive for the development of disposable devices or for temporal usage in biomedicine or biophotonics.