New Article in Nature Communications

posted Jan 7, 2014, 3:26 AM by Shin-Hyun Kim   [ updated Jan 7, 2014, 3:26 AM ]
Shin-Hyun Kim,   Jin-Gyu Park, Tae Min Choi, Vinothan N. Manoharan, and David A. Weitz, "Osmotic-pressure-controlled concentration of colloidal particles in thin-shelled capsules," Nature Communications, 5:3068 (2014). [pdf

Colloidal crystals are promising structures for photonic applications requiring dynamic control over optical properties. However, for ease of processing and reconfigurability the crystals should be encapsulated to form “ink” capsules rather than confined in a thin-film. Here, we demonstrate a class of encapsulated colloidal photonic structures whose optical properties can be controlled through osmotic pressure. The ordering and separation of the particles within the microfluidically-created capsules can be tuned by changing the colloidal concentration through osmotic pressure-induced control of the size of the individual capsules, modulating photonic stop-band. The rubber capsules exhibit a reversible change in the diffracted color, depending on osmotic pressure, a property we call osmochromaticity. The high encapsulation efficiency and capsule uniformity of this microfluidic approach, combined with the highly reconfigurable shapes and the broad control over photonic properties, make this class of structures particularly suitable for photonic applications such as electronic inks and reflective displays.