Three-dimensional direct current invisibility cloak produced with bulk materials

By virtue of eliminating the characteristic signals of physical objects, invisibility cloaks can also prevent the objects from being detected by instruments using electrical current. However, most existing designs of direct current cloaks cannot be directly applied in the natural environment. In this paper, we present a three-dimensional direct current cloak by solving Laplace equation in electric conduction. The cloak is composed of a bilayer structure with homogeneous and isotropic bulk materials. The designed structure, having withstood both conventional electrical potential measurements and tests by a commercially-available detector, is highly effective in suppressing current characteristic signals in close simulation of natural environmental conditions. The cloak is expected to facilitate the study of characteristic signal control in medical and geological research in the field of current detection, such as tumor diagnosis and mineral exploration. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.