Efficient solar-to-thermal management on femtosecond laser composite fabrication of hierarchical Janus plates

Abstract

Photothermal conversion materials can efficiently convert solar energy into directly usable heat energy, thereby reducing carbon emissions. However, most photothermal conversion materials are complex to prepare and have a long cycle, and their photothermal performance is not ideal. These problems limit their practical application. Herein, we propose a simple and controllable strategy for preparing photothermal conversion materials. We fabricated a stainless-steel-based graded superhydrophobic Janus photothermal plate that enhanced solar energy utilization through asymmetric surface engineering. Specifically, the upper surface combines femtosecond laser texturing with nanoparticle embedding of candle soot, achieving exceptional light absorption (∼98.54%) and robust superhydrophobicity (water contact angle: ∼158° and rolling angle: ∼3.5°). The lower surface is laser machined in a single pass to enhance the emissivity (ε = 0.92), facilitating the rapid transfer of heat into the enclosed space. Systematic evaluations revealed that the UL configuration achieved an internal temperature of 54 °C under 1.5 sun illumination. Agricultural trials demonstrated its practical efficacy: pumpkin seeds in the UL chamber showed 80% germination within 5 days, with accelerated growth rates. This research provides a scalable solar thermal management strategy for applications such as precision agriculture, building climate control and wearable technology, helping to advance sustainable energy solutions.