Space-Time Thermal Binary Coding by a Spatiotemporally Modulated Metashell

The recently proposed space-time-coding electromagnetic metasurface introduces the temporal dimension into artificial structure design, greatly expanding its digital application in information processing. However, the counterpart in thermal digital metamaterial is still lacking but compelling because the absence of temporal dimension prohibits synergetic modulation of thermal signal in time and space, thus limiting the capacity of information storage and the efficiency of information transmission with heat. Here, we introduce the temporal modulation into existing spatially variable thermal coding structures and propose a space-time thermal binary coding scheme. We design a category of coding units with time-dependent metashells so that they can switch their functionalities between cloaking and concentrating in time sequences. Integrating these identical units on a two-dimensional spatial array, we numerically show that this single metasurface can output various digital signal sequences composed of 0 and 1 in time and space dimensions. We further experimentally realize the temporal modulation with a rotatable concentric multilayered structure driven by a time-stepping motor. These results demonstrate a practical space-time strategy for thermal binary coding, provide a feasible prototype for spatiotemporal regulation of thermal signal, and promisingly open an alternative way for realizing information processing in diffusion systems.