Speleothem-Inspired Copper/Nickel Interfaces for Enhanced Liquid–Vapor Transport by Marangoni and Soret Effects

Geological formations have superior wickability and support the absorption of water and oils into narrow spaces of Earth's crust without external assistance. In this study, we present speleothem inspired heterogeneous porous and wicked copper (Cu)/nickel (Ni) interfaces for enhanced nucleate boiling of water/ethanol mixtures for energy-efficient separation processes. The incorporation of Ni strands within the copper particle matrix significantly enhanced heat transfer. Compared to plain copper, the Cu/Ni speleothem surfaces exhibited a 61% increase in the heat transfer coefficient for water/ethanol mixtures and a 332% increase for water, with a 58% faster onset of nucleate boiling. This enhancement was attributed to Marangoni and Soret effects at the Cu/Ni interfaces, driven by surface tension and concentration gradients. Furthermore, the synergistic wicking action of the Ni strands facilitated rewetting of the surface, replenishing liquid to the porous nucleation sites and preventing surface dry-out, thereby improving the overall heat transfer performance.