Camouflage thermotics: A cavity without disturbing heat signatures outside

Abstract

Cloaks can protect objects without disturbing heat signatures outside cloaks, and hence, objects are invisible to outside detection. However, cloaks themselves are visible to inside detection because they possess different heat signatures from the outside. This fact limits applications. Here, we solve this problem in thermotics by developing a different theory and then propose the scheme of thermal supercavity, a cavity without disturbing heat signatures outside. We investigate different supercavities with various shapes in two or three dimensions and validate the desired effects by simulations and experiments. We further design the scheme of super-invisibility which makes the cavity itself also invisible to inside detection. Moreover, our scheme simplifies the complicated parameters of non-circle shaped cloaks, which requires only two natural materials with a simple layer structure. Our work is useful for achieving new kinds of thermal devices, including thermal camouflage and designing similar supercavities in magnetostatics, electrostatics, particle diffusion, etc.

Designing effective thermal conductivity of materials of core-shell structure: Theory and simulation

“…In fact, low-dimensional heat transfer at a microscopic scale has been found to have many unique properties, such as the nonconvergence effect and size effect of the thermal conductivity [23]. However, the uniqueness of low-dimensional heat transfer has never been discovered at a macroscopic scale, such as thermal metamaterials including but not limited to thermal cloaks [5][6][7][8][9][10], thermal concentrators [6,[11][12][13][14], and thermal camouflage [15][16][17][18][19][20][21]. Therefore, type C golden touch might open a gate to explore unique properties in low-dimensional heat transfer at a macroscopic scale.…”

“…In this work, we focus on the thermal property of the coreshell structure, i.e., effective thermal conductivity. In fact, * jphuang@fudan.edu.cn research on artificial structures has realized many unique phenomena, such as thermal cloaks [5][6][7][8][9][10], thermal concentrators [6,[11][12][13][14], thermal camouflage [15][16][17][18][19][20][21], etc. Differently from these, we carefully design the anisotropic shell to realize golden touch, especially when the thermal conductivity of the shell is abnormal (κ θθ /κ rr < 0 for two dimensions and κ θθ /κ rr < −1/8 for three dimensions).…”

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.…”

Thermal magnifier and external cloak in ternary component structure

“…Heat energy is everywhere in nature, and hence its effective control is of great significance, especially for easing the energy issues. Fortunately, thermal metamaterials provide powerful methods to explore novel thermal phenomena, such as thermal cloak, [1][2][3][4][5][6][7][8][9] thermal rotator, 5,10 thermal camouflage, [11][12][13][14][15][16][17][18] thermal bending, [19][20][21] thermal lens, 22 etc. Among them, bilayer thermal cloak 7-9 is a representative one which largely simplifies the structure as required by transformation thermotics.…”