Stretchable Photonic Semicrystal Interface by Pressure-Assistant Self-Assembly

Stretchable structural colors that can dynamically respond to mechanical stimuli are garnering interest as energy-free mechanical-optical sensors. Typical technologies for embedding photonic crystals (PCs) in elastic hydrogels generally involve etching processes, which have raked controversy for straying from green manufacturing practices. Here, a facile pressure-assisted self-assembly strategy to fabricate an interfacial photonic structure, i.e., semicrystalline photonic structure (SPS), consisting of two diffraction nanopatterns, including randomly oriented, medium-scale ordered PCs and arbitrarily distributed amorphous photonic glass using hydrophilically modified colloidal polystyrene (PS) nanospheres configured at the hydrogel interface is introduced. The structural colors of the SPS hydrogel interfaces undergo immediate and repeatable mechanochromic redshift or blueshift in real time when the sample is longitudinally compressed or tensed, respectively, at both the micro zone and macroscopic color block levels. The SPS hydrogel interfaces display long-term colorfast, angle-independent, or non-iridescent coloration and bright structural colors in a high reflective-intensity range of 62%–96% at a normal viewing angle. With these features, this study demonstrates the feasibility of fabricating SPS hydrogel interfaces with mechanical and optical properties that are compatible with state-of-the-art stretchable optical sensors.