Manipulating DC Currents with Bilayer Bulk Natural Materials

Abstract

Abstract:The principle of transformation optics has been applied to various wave phenomena (e.g., optics, electromagnetics, acoustics and thermodynamics). Recently, metamaterial devices manipulating dc currents have received increasing attention which usually adopted the analogue of transformation optics using complicated resistor networks to mimic the inhomogeneous and anisotropic conductivities. We propose a distinct and general principle of manipulating dc currents by directly solving electric conduction equations, which only needs to utilize two layers of bulk natural materials. We experimentally demonstrate dc bilayer cloak and fan-shaped concentrator, derived from the generalized account for cloaking sensor. The proposed schemes have been validated as exact devices and this opens a facile way towards complete spatial control of dc currents. The proposed schemes may have vast potentials in various applications not only in dc, but also in other fields of manipulating magnetic field, thermal heat, elastic mechanics, and matter waves.Controlling electromagnetic (EM) fields so as to render an object invisible, has been a long-standing dream for many researchers over the decades [1,2] . On the basis of the invariance of Maxwell's equations where equivalence is established between metric transformations and changes in material parameters, transformation optics [3] and conformal mapping [4] have been 2 developed to manipulate EM wave propagation in a practically arbitrary manner. 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, the dc magnetic cloak is theoretically investigated [12] and experimentally realized using superconductors and ferromagnetic materials [13,14] . By using the same materials as dc magnetic cloak, the theoretical realization of a dc magnetic concentrator is also demonstrated [15] . On the basis of form invariance of the heat conduction equation, transformation thermodynamics is investigated to manipulate diffusive heat flow [16] ; through tailoring inhomogeneity and anisotropy of conductivities, transient thermal cloaking has been experimentally demonstrated [17] . In addition, manipulation of heat flux with only two kinds of materials (by utilizing a multilayered composite approach) has been ...

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.…”

Diffusive-light invisibility cloak for transient illumination

“…Conversely, the thermal analogs of the considered diffusive cloaks would only demand an engineered diffusivity. It is worth mentioning that there exist alternative cloaking techniques that can also relax the implementation complexity of thermal cloaks [34,35], as well as of dc current cloaks [36].…”

Towards omnidirectional, large scale, full polarization, and broadband practical invisibility cloaks: challenges and progress

“…For example, the superluminal phase propagation does not need be to considered for the diffusive-light cloak [79]; the dc magnetic cloaks [80][81][82] and dc current cloaks [83][84][85][86] work for static fields, so phase preservation requirement and bandwidth issue are not applicable. The electromagnetic surface waves [87] cloak works for surface waves and so it does not need to consider the bandwidth and omnidirectional requirements.…”