Self-cleaning hierarchical thermal cloak.

Abstract

Thermal invisibility has captivated the research interest for decades. Recent theories envisioned the promising schemes for this purpose using the near-wavelength antennas; because it enabled precise control over the radiation for invisibly cooling while preserving the cloaking within detectable band. However, pushing this delicate device to real-world applications raises two essential challenges: large-scale fabrication of the structures featuring nanoscale accuracy and durably safeguarding the function from both erosion and various contaminant intakes. Here, we report a self-cleaning hierarchical thermal cloak using femtosecond laser direct writing. The cloak is engineered with finely configured dynamic superhydrophobic micropillar arrays; on top of the micropillars, the antennas are devised for direct tailoring to ensure the large-area manufacturing scalability and feasibility. We demonstrate that the co-created architecture has superior cloaking performance with boosted mechanical and thermodynamic durability; moreover, it enables self-sweeping of the contaminants through van der Waals forces of an impact bulk droplet, thus completely regaining the excellent thermal cloaking. Notably, both the self-cleaning and cloaking functionalities remain robust even after over 24 hours of harsh treatments, including UV irradiation, water-flow flushing and thermal cycling.