(774e) Bioinspired Composite Materials with Stimuli-Responsive Color Changing Ability

The ability of changing colors is one of the most exciting features of advanced living organisms. Octopuses, chameleons, squids, all possess cells that can alter their colors. In some cases, the color changing mechanism is due to the ability of these cells to displace pigments over different areas, as in the case of chromatophores in the octopus. In other cases, the change in color is due to a change in the spacing of colloidal crystals, as in the chameleon iridophores. Inspired by this ability, we present here composite materials, consisting of a polymer matrix (PMMA or fluorinated acylates) containing water droplets. These droplets, with a size of tens of micrometers, contains different responsive particles. When magnetic colloids are incorporated, the application of magnetic field gradients will lead to a displacement of the colloids, similar to the displacement of pigments in chromatophores.

When instead temperature-responsive PNIPAm microgels are incorporated into the droplets, at sufficiently high volume fraction they will form colloidal crystals. These crystals create iridescent colors because of the length of the spacing between particles interfering with light. Because the size of the microgels are temperature responsive, the colloidal crystals can be destroyed at a temperature higher than the lower critical solubility temperature, leading to a change in color. Additional stimuli-responsive particles can be used to induce different stimuli-responsive color-changing mechanisms.

The proposed approach is thought to be a novel design for stimuli-responsive composite materials with color-changing ability.