Full Control and Manipulation of Heat Signatures: Cloaking, Camouflage and Thermal Metamaterials

Abstract

Thermal camouflage and cloaking can transform an actual heat signature into a pre-controlled one. A viable recipe for controlling and manipulating heat signatures using thermal metamaterials to empower cloaking and camouflage in heat conduction is demonstrated. The thermal signature of the object is thus metamorphosed and perceived as multiple targets with different geometries and compositions, with the original object cloaked.

Thermal cloak-concentrator

“…So far, the steady-state thermal cloak [8] and its theoretical extensions [9,10] have been experimentally realized or developed [11][12][13][14][15]. Meanwhile, researchers also designed a lot of thermal metamaterials with novel thermal characteristics beyond cloaking [9][10][11][16][17][18][19][20][21][22][23][24], such as concentrators [10,11,16]. The concentrator helps to focus heat flux in a particular region, and thus yields a higher temperature gradient inside the region, which can be used to improve the efficiency for thermal-to-electrical conversion (the Seebeck effect [25,26]).…”

“…Unfortunately, the existing thermal metamaterials published in the literature [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] don't have the essential feature of intelligence, namely, they lack the ability to automatically sense and respond to the change of environmental temperature. The reason is that within the framework of transformation thermotics (or thermodynamics as also named by some other famous scholars) [8,10], the property of thermal metamaterials can influence the temperature field, but not vice versa due to temperature-independent thermal conductivities under consideration.…”

Converting the patterns of local heat flux via thermal illusion device

“…As a result, much attention has been paid by theorists and experimentalists, [2][3][4][5][6][7][8] and there come out a lot of thermal metamaterials with novel thermal properties beyond cloaking, 6,10-13 such as concentrators (which are used to enhance the temperature gradient in a specific region), 3,14 inverters (which allow heat to apparently flow from a colder to a warmer region without violating the second law of thermodynamics), 1,15 rotators (which can rotate the flow of heat as if the heat comes from a different direction), 3,15 and camouflage. 16 Controlling the flow of heat enlightens us to design an illusion device for thermal conduction. As known to us, by using some special approaches one can replace object A's scattering pattern by object B's, which is the basic of optical illusion.…”

Broadband Acoustic Cloaking within an Arbitrary Hard Cavity

“…More recently, the research on cloaking has been extended to flexural waves, where also reduced cloaks have been proposed [13] and experimentally reported [14]. The theoretical tool of coordinate transformation also has been extended to other areas of physics, such as heat flux, where thermal cloaking and thermal camouflage have been proposed [15,16] and experimentally realized [16,17].…”