Directional control of near-field energy transfer enabled by ultra-thin carbon nanotube films

Single-walled carbon nanotube films (CNFs), as ultra-thin and transdimensional material platforms, exhibit anisotropic electromagnetic modes in wave vector space, offering potential for directional control of energy transfer. In this work, we construct a heat exchange system consisting of nanoparticles (NPs) and a semi-enclosed cavity composed of two single-walled CNFs, and systematically investigate how to control the directionality of energy transfer through CNFs. We find that due to the excitation of cavity modes, the radiative heat transfer (RHT) between NPs in the presence of the semi-enclosed cavity is more than twice that of a single-layer CNF, and significantly higher than that of other cases. Also, through the study of the chiral index and the separation spacing between nanotubes, we find that RHT can be greatly regulated by rotating CNFs. When the rotation angles of the two CNFs are $16.5°$ and $163.5°$, respectively, the enhancement ratio of RHT can surpass four orders of magnitude. In addition, a multi-terminal radiative thermal router for energy splitting is proposed based on CNFs. By rotating CNFs, the RHT between the heat source and different receiving terminals can be directionally controlled. When the angular misalignment is fixed at $147°$, the thermal router can achieve a splitting ratio of 86% and the total RHT is higher than that of other cases. These findings may provide practical solutions for directional control of contactless energy transfer between thermal elements in functional thermal devices.