Fig. 8.

3D photonic crystals for mechanochromic applications. a Scheme of 3D photonic crystal with reversible lattice of polystyrene beads in a PDMS matrix. The lattice is controlled by stretching or releasing PDMS matrix. b Peak positions of reflected wavelength are shifted by elongating the photonic crystal embedded PDMS. c An illustration of silica particle arrays under deformation. Optical microscope images of 3D photonic crystal embedded PEGMA gel under pushing or pulling. d 3 × 3 pixels with the PEGMA photonic crystal gel

(Figure reproduced from a, b [67], Copyright 2006, American Chemical Society; c, d [69], Copyright 2014, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)