Photonic Papers and Inks: Color Writing with Colorless Materials
(Under Construction: Ian Burgess, Spring 2012)
H. Fudouzi, Y.N. Xia, Photonic Papers and Inks: Color Writing with Colorless Materials, Advanced Materials, 15, 892-896 (2003).
This paper describes a technique to exploit solvent swelling of an elastomeric matrix as a photonic ink, capable of writing color patterns while each component material is "colorless" (i.e. does not absorb visible light).
The ink/paper system is based on an elastomeric matrix (polydimethylsiloxane, PDMS) that contains an embedded regular lattice of polystyrene (PS) microshperes. A scanning electron micrograph (SEM) of the structure is shown in the figure below (left figure, B). This dielectric superstructure with wavelength-scale periodicity acts as a photonic crystal, exhibiting color due to a strong Bragg reflection peak in the visible region of the spectrum. Since the apparent color is directly due to Bragg reflection, it is very sensitive to physical properties of the system that control the optical pathlength of periodicity.