Full‐Parameter Omnidirectional Thermal Metadevices of Anisotropic Geometry

Abstract

Since the advent of transformation optics and scattering cancelling technology, a plethora of unprecedented metamaterials, especially invisibility cloaks, have been successfully demonstrated in various communities, e.g., optics, acoustics, elastic mechanics, dc electric field, dc magnetic field, and thermotics. A long-held captivation is that transformation-optic metamaterials of anisotropic or noncentrosymmetric geometry (e.g., ellipsoids) commonly come along with parameter approximation/simplification or directional functions. Here, a synthetic paradigm with strictly full parameters and omnidirectionality is reported simultaneously to address this long-held issue for molding heat flow and experimentally demonstrate a series of noncentrosymmetric thermal metadevices. It changes the usual perception that transformation thermotic/dc/acoustic metamaterials are just a direct and simplified derivatives of the transformation-optic counterpart. Instead, the proposed methodology solves an intriguingly important and challenging problem that is not possibly achievable for transformation-optic metamaterials. The approach is rigorous, exact, robust, and yet elegantly facile, which may open a new avenue to manipulating the Laplacian and wave-dynamic fields in ways previously inconceivable.

Transformation Omnithermotics: Simultaneous Manipulation of Three Basic Modes of Heat Transfer

“…Transformation theory does not restrict shapes, so these omnithermal devices can be extended to other complex shapes such as ellipses. 16,17 Certainly, the present theory can also deal with any combination of the three basic modes of heat transfer as long as the transformation rules are satisfied. As experimental demonstrations, one may resort to the heat transfer in aerogels.…”

“…Transformation theory, as a general and powerful methodology, has already been extended from wave systems (e.g., electromagnetic propagation 6 ) to diffusion systems (e.g., heat conduction 7,8 ), thus yielding the rapid development of thermal metamaterials or metadevices, 9 such as cloaks, [10][11][12][13][14][15][16][17][18] concentrators, 10,[18][19][20][21] rotators, 10,18 camouflaging, [22][23][24][25][26][27][28] and guiding. [29][30][31] However, these thermal metamaterials take only conductive effects into consideration.…”

Non-Singular Homogeneous Polyhedral Heat Cloak and Its Realization

“…The bilayer strategy was then extended to the design of full-parameter omnidirectional elliptical cloaks. 34 These authors advanced significantly this field. The bilayer method they proposed is direct and easy to realize with natural materials.…”

“…[23][24][25][26] Researchers have then made great achievements on heat manipulation with various thermal metadevices. [27][28][29][30][31][32][33][34][35][36] The pioneering works mainly focused on regular shaped cloaks, i. e. cylindrical and spherical cloaks. Cloaks with more complicated boundaries were then studied in the field of electromagnetism and acoustics.…”

Three-Dimensional Illusion Thermotics with Separated Thermal Illusions

“…In transformation thermotics, the isotropic virtual space is transformed into the anisotropic real space with maintaining the heat conduction governing equation from Ñ Ñ Ñ Ñ (κ• T ) = 0 to '(κ'• ' T' ) = 0, giving rise T to the transformed thermal conductivity κ' = ΛκΛ /det(Λ), where Λ is 14 the transformation Jacobian matrix as Λ = . Based ∂(x', y', z')/ ∂(x, y, z) on transformation thermotics, people have extended to the illusion thermotics to design the related illusion devices to move the target, or to change the target shape, or to design the equivalent elements, or to cloak the target, while maintaining the same temperature field outside 5,8,[16][17][18][19][20][21][22][23][24][25][26][27] the device.…”