Experimental Demonstration of a Multiphysics Cloak: Manipulating Heat Flux and Electric Current Simultaneously

Abstract

In past years, triggered by their successful realizations in electromagnetics, invisible cloaks have experienced rapid development and have been widely pursued in many different fields, though so far only for a single physical system. In this letter we made an unprecedented experimental attempt to show a multidisciplinary framework designed on the basis of two different physical equations. The proposed structure has the exceptional capability to simultaneously control two different physical phenomena according to the predetermined evolution scenarios. As a proof of concept, we implemented an electric--thermal bifunctional device that can guide both electric current and heat flux "across" a strong 'scatter' (air cavity) and restore their original diffusion directions as if nothing exists along the paths, thus rending dual cloaking effects for objects placed inside the cavity. This bifunctional cloaking performance is also numerically verified for a point--source nonuniform excitation. Our results and the fabrication technique presented here will help broaden the current research scope for multiple disciplines and may pave a prominent way to manipulate multiple flows and create new functional devices, e.g., for on--chip applications. The state and evolution of one physical phenomenon (wave or flux) are fundamentally determined by their manner of interaction with surrounding matters abiding different physical theorems or laws, mathematically described by different characteristic equations, such as Maxwell's equations for electromagnetic (EM) waves or conduction equation for current/heat flow. According to Einstein's theory of general relativity, these differential equations representing basic physical laws will experience formality invariance (but with their parametrical coefficients changed) if transformed among different coordinate systems [1,2]. The covariance of free--space Maxwell's equations successfully explains the constant nature of light velocity in different inertia systems [3] and also led to the important conclusion that wave behaviors in curved empty geometries are equivalent to electromagnetism in a medium [4,5]. In 2006, Pendry and Leonhardt developed this important conception on coordinate mapping with their independent proposals that light could be bent to realize invisible cloaking [6,7], which was quickly verified in the experiment [8]. This scientific milestone on cloaking has triggered enormous research enthusiasm on transformation optics (TO) and their technological applications associated with the development of metamaterials [9,10], which has greatly contributed to the advancement of modern electromagnetism [11]. In past years people working in this field were mostly endeavored to improve the practicality of EM cloaks with various versions of designing algorithms and have successfully demonstrated the cloaking effect covering nearly the whole frequency range from static to visible light [12--21]. In addition to EM cloaks, other instrumental EM devices with functionalities deemed impossible ...

Room-temperature broadband quasistatic magnetic cloak

“…17,18 The efficiency of the bilayer approach proposed by the first group was quickly verified and applied to other Laplace equations governing the evolutions of different physical phenomena. [25][26][27][28][29][30][31] In practice, a magnetic cloak that is able to perform under alternating currents will be more meaningful, as one usually relies on EM induction to uncover hidden metallic or magnetic objects. The same group extended their original two-dimensional bilayer design to A.C. fields and indicated a technical possibility within a frequency range of several hundred Hertz.…”

Invisible Sensors: Simultaneous Sensing and Camouflaging in Multiphysical Fields

“…This multiphysical invisible sensor has three features that distinguish it from conventional DC and thermal metamaterial devices, especially different from the bifunctional cloak for an air cavity. [ 40 ] First, we allow the sensor to "see through and behind" the cloaked region in multiphysical fi elds. As a result, the sensor is invisible and receives proportional incoming signals at the same time, and it is able to "open its eyes" behind the cloak to receive information from the outside multiphysical When a sensor is used to probe a physical fi eld, it intrinsically disturbs surrounding environment, introduces perturbation and unwanted noise in the measurement.…”

“…Later, the fi rst experiment was carried out to simultaneously cloak an air cavity in the electric and thermal fi elds. [ 40 ] This sample was fabricated through a sophisticated man-made metamaterial structure with many holes drilled in a silicon plate that were, then, fi lled with poly(dimethylsiloxane) (PDMS). In our work, we found that natural materials with simple structure can also simultaneously manipulate multiphysical fi elds.…”

Temperature-Dependent Transformation Thermotics: From Switchable Thermal Cloaks to Macroscopic Thermal Diodes

“…This process allows us to design switchable thermal cloaks and then macroscopic thermal diodes. The former serve as an extension of the extensively investigated cloaks without switches [16][17][18][19][20][21][22][23]31]; the latter are actually a useful application of the former in this work. We proceed as follows.…”

“…The cloaking originates from the fact that the thermal conduction equation remains form-invariant under coordinate transformation. So far, the theoretical proposal of steady-state thermal cloaking [16] and its extensions (say, bifunctional cloaking of heat and electricity [17] or nonsteady-state thermal cloaking [18]) have been experimentally verified and developed [19][20][21][22][23]. The theoretical treatment based on coordinate transformation [16][17][18][24][25][26][27][28], which is called transformation thermotics (or transformation thermodynamics), has a potential to become a fundamental theoretical method for macroscopically manipulating heat flow at will.…”