Bioinspired Robust Sealed Colloidal Photonic Crystals of Hollow Microspheres for Excellent Repellency against Liquid Infiltration and Ultrastable Photonic Band Gap

Inspired by the limpet's shell, this study reports an inexpensive and straightforward strategy to create sealed photonic crystals from colloidal hollow microspheres. From the mechanically sealed structure and the periodically isolated air microcavities, the resulting sealed colloidal crystals show enhanced mechanical robustness and an ultrastable photonic band gap. In contrast to the sensitivity and the concomitant tuning capability in conventional opals and inverse opals, the sealed structure repels any liquid, even under high pressure, resulting in ultrastable photonic band gap properties. Moreover, with surface modification, its self-cleaning ability prevents the deterioration of iridescence resulting from surface pollution. This novel photonic structure shows its potential utility in applications requiring an ultrastable photonic band gap in an extreme environment. This study demonstrates this by photonic crystal lasing at a constant wavelength for a sealed crystal, whether dry in air or submerged in water.