Thermal theory for heterogeneously architected structure: Fundamentals and application

Abstract

Architected structures have aroused widespread research interest because they possess unique properties in mechanics. However, a fundamental theory describing their thermal properties has not been established. Here, we present a theoretical framework in thermotics to predict thermal properties of architected structures. Then, by experiment and simulation, we show its applications in the field of heat management. By assembling two radically different materials, we design two types of Janus structures. The different rotation degrees of the Janus structures can flexibly control the switch between different functions, such as from partial concentration to uniform concentration and from rotation to concentration. These functions are realized in a structure made of a heterogeneous core plus a homogeneous shell, which is in contrast to the existing structures made of a homogeneous core plus a heterogeneous shell designed according to the theory of transformation thermotics. This work lays a theoretical foundation in thermotics for further research on heterogeneously architected structures, and it proposes the concept of thermal Janus structures for flexible heat control, which may open an avenue for intelligent thermal metamaterials.

Metathermotics: Nonlinear thermal responses of core-shell metamaterials

“…In particular, the nonlinear modulation will be effectively enhanced under the thermal coupling conditions determined by Eqs. (10), (11) and Eqs. (19), (20).…”

“…Equations (10), (11) and Eqs. (13), (14) are two different thermal coupling conditions because they establish the relations among the core, shell, and matrix.…”

“…Figures 2(a1)-2(c1) show the nonlinear modulation under the thermal coupling condition determined by Eqs. (10), (11). According to the theoretical analysis of Eq.…”

“…The nonlinear modulation η can be well manipulated and enhanced under the thermal coupling condition determined by Eqs. (10), (11). Here the word "enhanced" means η > 1, which indicates that χ e (effective nonlinear coefficient) is counterintuitively larger than χ c (the core's nonlinear coefficient).…”

“…Fortunately, thermal metamaterials have provided a powerful method to tailor thermal conductivities with delicately designed structures. Based on thermal metamaterials, a large amount of novel thermal phenomena have been realized, such as thermal cloaks [1][2][3][4][5][6][7][8], thermal concentrators [3,4], thermal rotators [9,10], thermal transparency [11][12][13][14][15][16], thermal camouflage [17][18][19][20][21][22][23], thermal bending [24][25][26][27], etc. To achieve these phenomena, the core-shell structure serves as a typical scheme.…”