All-dielectric invisibility cloaks made of BaTiO3-loaded polyurethane foam

Transformation optics has led the way in the development of electromagnetic invisibility cloaks from science fiction to engineering practice. Invisibility cloaks have been demonstrated over a wide range of the electromagnetic spectrum, and with a variety of different fabrication techniques. However, all previous schemes have relied on the use of metamaterials consisting of arrays of sub-wavelength inclusions. We report on the first cloaking structure made of a high-κ dielectric-loaded foam mixture. A polyurethane foam mixed with different ratios of barium titanate is used to produce the required range of permittivities, and the invisibility cloak is demonstrated to work for all incident angles over a wide range of microwave frequencies. This method will greatly facilitate the development and large-scale manufacture of a wide range of transformation optics-based structures. S Online supplementary data available from stacks.iop.org/NJP/13/103023/ mmedia 3 Author to whom any correspondence should be addressed. 4 Current address: Department of Electrical and Computer Engineering, University of Texas at Austin, Austin, TX 78712, USA. 5 Current address: School of Engineering Science, University of Southampton, Southampton SO17 1BJ, UK. New Journal of Physics 13 (2011) 103023 1367-2630/11/103023+13$33.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft