EXC 3120 BlueMat - Research Topic C1: Tunable Microwave and MIR Permittivity by Control of Water Distribution

The nanoporous structures considered in BlueMat are orders of magnitude smaller than the wavelength of microwave and MIR radiation. Thus, we will utilize water-driven materials in the effective medium regime. In the microwave range, bulk water has a high permittivity of 80, attributed to the reorientation of water dipoles. The permittivity is expected to become anisotropic at interfaces, with the component orthogonal to the interface reducing to 2. Utilizing samples with anisotropic porosity, e.g., porous silica and alumina, we envisage for the first time experimentally clarifying this water anisotropy. In the MIR range, the permittivity of bulk water reduces to 2, but water is characterized by significant absorption with an attenuation length in the order of 10 ?m. We intend to employ polyolefin aerogels, which have intrinsically high transmittance in the MIR range, and add optical tunability via reversible adsorption of water on the surface of the aerogel. The key scientific questions are: How can we control the complex permittivity of water and its anisotropy by nanoconfinement? How can we utilize water and its confinement to tune the effective permittivity of nanostructured media? How can we utilize these effects to switch microwaves and thermal radiation?

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