A Negative Conductivity Material Makes a dc Invisibility Cloak Hide an Object at a Distance

Abstract

The theoretical design and the first experimental verification of an exterior dc invisibility cloak that can hide an object from dc detection at a distance are presented. Based on the transformation optics theory, the exterior dc cloak requires negative conductivity material to create folded geometry, which will cancel the real geometry of detected object in distance and make it invisible. Negative conductivities are designed and realized using active devices, together with resistor networks, to generate the equivalent conductivity materials required by the exterior dc cloak. An experimental sample of the dc cloak is fabricated on the printed circuit board and the measured result has excellent agreement with numerical and circuit simulations, showing very good cloaking performance at a distance.

Manipulating DC Currents with Bilayer Bulk Natural Materials

“…Soon after, an ultrathin dc electric cloak [21] and a dc electric concentrator [22] are reported using similar resistor networks. More recently, an exterior dc cloak [23] and an active dc cloak [24] have been experimentally realized by the use of inhomogeneous and anisotropic conductivities with the aid of active sources. It is noted that EM invisibility cloaks made of L-C networks have been experimentally demonstrated [25] .…”

“…Besides making objects invisible [1][2][3][4] , many other novel devices are rapidly emerging, with a representative one being a concentrator [5,6] that can enhance the energy density of incident waves in a given area. In addition to manipulation of EM waves [1][2][3][4][5][6] , the theoretical tool of coordinate transformation has been extended to other areas of physics (such as acoustic waves [7] , matter waves [8] and elastic waves [9] ).Recently, many significant achievements have been made in the manipulation of magnetostatic field [10][11][12][13][14][15] , thermal conduction [16][17][18][19] , and electrostatic field [20][21][22][23][24] . In 2007, Wood and Pendry proposed a dc metamaterial that pointed the way towards the design of static magnetic cloak [10] , and the dc metamaterial was experimentally verified soon afterwards [11] .…”

“…Recently, many significant achievements have been made in the manipulation of magnetostatic field [10][11][12][13][14][15] , thermal conduction [16][17][18][19] , and electrostatic field [20][21][22][23][24] . In 2007, Wood and Pendry proposed a dc metamaterial that pointed the way towards the design of static magnetic cloak [10] , and the dc metamaterial was experimentally verified soon afterwards [11] .…”

“…Our design schemes do not rely on transformation optics, and we can thus avoid the problems present in previous proposals (such as inhomogeneous and anisotropic parameters that need to mimicked via complicated resistor networks [20][21][22][23][24] ). Also, the proposed schemes, derived directly from the electric conduction equation, are exact rather than approximate ones.…”

Invisible Sensors: Simultaneous Sensing and Camouflaging in Multiphysical Fields

“…More recently, metamaterials were presented that control the DC current [18][19][20][21][22][23][24][25][26] and the heat fl ux. [27][28][29][30][31][32][33][34][35][36][37] However, these devices were designed to cloak an object in a single physical fi eld.…”