Interfacial Assembly of Amphiphilic Tiles for Reconfigurable Photonic Surfaces.

Nature has created photonic structures in cells and assembled them to make photonic layers for a living. Inspired from nature, we design amphiphilic photonic tiles and assemble them at air-water interface to compose highly reconfigurable photonic layers. The photonic tiles are prepared by photolithographically defining the shape of the disc using a photocurable dispersion of repulsive particles. The tiles are further treated by directional dry etching to selectively render top and side surfaces of the discs hydrophobic. The amphiphilic photonic tiles deform the air-water interface by gravity, which causes a strong attractive force driven by capillarity. Therefore, the tiles form two-dimensional (2D) dense-packing, which rapidly adapts dynamic fluctuation and shape change of the interface, providing highly reconfigurable photonic layers. In addition, the assembly can be transferred into target solid surfaces through the Langmuir-Blodgett method to make photonic coatings. Moreover, the amphiphilic tiles can be assembled on the surface of water drops, forming a photonic shell on liquid marbles which resembles photonic structures in nature. We believe that our strategy based on a 2D tile assembly at the free interface will provide a simple yet useful means to create photonic layers on various purposes.