EXC 3120 BlueMat - Research Topic C4: Scattering of Visible Light by Control of Water Distribution

Porous media with periodic or random structures comparable to the wavelength of light can provide spectrally selective scattering. Here, the optical response or color is no longer dictated by the base materials but by the pore shape, orientation, and arrangement, as well as by pore filling. Embedding water into the pore space and controlling its distribution at the nm- and ?m-scale allows for modifying the scattering, thus opening new possibilities to dynamically adjust or switch optical appearance. Previously, water has only been used to slightly shift the spectral response of periodic media upon water infiltration. However, here, we plan to go beyond this state of the art, achieving broadband control of the spectral response and even switching the color on and off. In this respect, we aim to achieve a similar functionality as in the skin of chameleons or cephalopods, but using water in porous media. The key scientific questions are: How can we design and fabricate structures with self-organized multiscale porosity to have defined optical appearance? How can we control water distribution in multiscale porous framework structures to switch this optical appearance? How can we utilize these effects for switchable structural color and opacity, including adaptive functionality?

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