These make up the core of the core-shell nanoparticle colloids, and they are what physically scatter the light in Manoharan’s photonic pigments. The polystyrene nanoparticles are surrounded by a shell of poly(N-isopropylacrylamide-co-acrylic acid) or poly(NiPAm-AAc). This shell is transparent, so light can pass through it. It is also soft and can squish as the core-shell particles pack together. Modifying the distance between the polystyrene cores, by varying the shell thickness, makes them reflect different wavelengths of light, thereby producing different colors. Jin-Gyu Park, a postdoc in the Manoharan lab, and Shin-Hyun Kim, currently a professor at Korea Advanced Institute of Science & Technology, came up with a way to use microfluidics to encapsulate an aqueous suspension of the core-shell nanoparticles within an ultraviolet-curable monomer, ethoxylated trimethylolpropane triacrylate.
by Bethany Halford |
April 28, 2014