Abstract
Transformation theory, succeeding in multiple transportation systems, has enlightened researchers to manipulate the field distribution by tailoring the medium’s dominant parameters in certain situations. Therefore, the science community has witnessed a boom in designing metamaterials, whose abnormal properties are induced by artificial structures rather than the components’ characteristics. However, a majority of such meta-devices are restricted to the particular physical regimes and cannot sense the changes taking place in the surrounding environment and adjust its functions accordingly. In this article we propose a multi-physics bi-functional “intelligent” meta-device which can switch its functions between an invisible cloak and a concentrator in both thermal and DC electric conduction as the ambient temperature or voltage varies. The shape memory alloys are utilized in the design to form a moveable part, which plays the crucial role in the switching effect. This work paves the way for a practicable method for obtaining a controllable gradient of heat or electric potential, and also provides guidance for efficiently designing similar intelligent meta-devices by referring to the intriguing property of shape memory alloys.
Highlights
Controlling the spatial distribution of the physical fields at will is an exciting challenge for human beings, which leads to vital progress in understanding the underlying mechanism of specific phenomena and to great values of applications in improving our daily life
One may find the values of the κ/σ of different metals are not strictly equivalent as implicated by Wiedemann-Franz law, and due to the mismatch of the thermal and the electrical conductivities one may worry about that the device consisting of these materials cannot perform perfectly in both thermal and electric fields
This fact has been mentioned by Yang et al [28] before. They point out a method to solve the problem by mixing another material with a higher value of κ/σ on the interface
Summary
Controlling the spatial distribution of the physical fields at will is an exciting challenge for human beings, which leads to vital progress in understanding the underlying mechanism of specific phenomena and to great values of applications in improving our daily life. In 2006, Leonhardt and Pendry et al [1,2] propose a concept named transformation theory, which implies a practicable method to build an invisible cloak based on the fact that Maxwell equations can retain their forms invariant under a coordinate transformation This advancement has shed a light on the design of metamaterials, which are a sort of artificial materials possessing intriguing properties originating from their special structures rather than their intrinsic characteristics and has been rapidly theoretically generalized and applied to different physical fields such as electromagnetic [3,4,5,6], and acoustics [7]. Through this manipulation we can produce a unique class of intelligent thermal or electrical metamaterials which permit the device to automatically alter from a thermal/electrical cloak to a concentrator or vice versa, as the ambient temperature varies
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