Ultra‐Durable High‐Performance Dropwise Condensation Heat Transfer Enabled by a Solid‐State Super‐Slippery Surface With Nanoscale Through‐Thickness Compositional Gradient

ABSTRACT The durability of micro/nano‐structured superhydrophobic surfaces and slippery liquid‐infused surfaces remains a great challenge, due to irreversible flooding‐driven failure and the drainage loss of lubricants, respectively, for enhanced condensation heat transfer. Here, we propose a strategy for designing a nano‐gradient solid‐state super‐slippery (NSS) coating, with a nanoscale through‐thickness compositional gradient, applicable to substrates of different roughness levels and materials, as fabricated via plasma‐enhanced chemical vapor deposition, to enable highly‐efficient dropwise condensation. Enabled by the low thermal resistance (only ∼300 nm thick in total), high droplet shedding frequency, and small initial sliding diameter, we achieve a stable 20% higher condensation heat transfer coefficient (HTC) on the NSS surface than that on a superhydrophobic surface over a wide subcooling range from 2 to 8 K, and a >100% HTC enhancement compared to that of filmwise condensation on a hydrophilic surface. With the nano‐gradient functional design, the NSS surface also exhibits ultra‐high thermal and mechanical durability under harsh conditions, surviving rigorous heating tests with only a 20% HTC deterioration after being heated at 250°C for 240 h, and maintains stable condensation performance over a 2‐month continuous test. This facile yet effective strategy enables ultra‐durable high‐performance dropwise condensation heat transfer for industrial applications.