Photonic papers and inks: Color writing with colorless materials

A photonic paper/link system for color writing on and with colorless materials is described. The paper is a 3D crystal of polymer beads embedded in an elastomer matrix mode of poly(dimethylsiloxane) (PDMS), and the ink is a liquid (e.g., a silicone fluid or organic solvent) capable of swelling the matrix, changing the lattice constant and hence wave-length of light diffracted (see Figure and cover).