A Dual-Layer Janus Mesh–Wedge Microgroove Surface for Spontaneous Departure and Directional Transport of Condensate

Sustainable dropwise condensation technology is crucial for applications in high-performance thermal management, energy conversion, and desalination. However, conventional condensation surfaces often suffer from low droplet departure efficiency and gravity dependence, limiting their practical application in advanced heat exchangers. Here, we report a dual-layer composite surface, composed of a slippery Janus copper mesh and a wedge-shaped microgrooved substrate (SJM-WM), which enables gravity-independent droplet departure via interfacial transport. This design spatially decouples vapor condensation on the upper Janus mesh and droplet transport in the lower substrate, leveraging synergistic wettability gradients and Laplace pressure-driven directional flow. By tailoring mesh pore size, the Laplace pressure and droplet coalescence dynamics are effectively regulated, achieving a small droplet departure diameter of 98 ± 2 μm, which is comparable to the bouncing-off behavior on superhydrophobic surfaces. The SJM-WM surface enhances condensation heat transfer by 23.1% and 102.4% compared to state-of-the-art hydrophobic-superhydrophilic wedge-grooved surfaces (HB-SHL) and hydrophobic copper mesh-wedged microgroove composite surfaces (HBM-WM), respectively. This work provides a promising strategy for advancing high-performance thermal management systems in power-dense electronics.