Evolution of the water cluster in pore condensation

Pore condensation enables vapor-liquid transitions below saturation humidity, yet the microscopic dynamics of the embryo formation and cluster growth within the pore remain unresolved. Through molecular simulations on tunable-wettability surfaces ((Formula presented.) – (Formula presented.)), we discover that wettability influences condensation kinetics: reducing contact angles from (Formula presented.) to (Formula presented.) decreases the molecular displacement by (Formula presented.) 60% and the molecular potential energy by (Formula presented.) 10% for the condensed water molecules, increasing vapor capture tenfold. Pores enhance nucleation on hydrophobic surfaces ((Formula presented.)) by restricting molecular mobility, an effect attenuated with increasing wettability. Specifically, we identify four distinct cluster evolution modes: intra-pore (confined growth), on-plane, tumble (pore-to-pore migration), and bounce. Analysis of the above modes reveals that spatial confinement accelerates initial nucleation but suppresses later-stage coalescence. As a result, the cluster growth rate of the intra-pore mode can be initially higher than that of the flat reference but later drops below. This work establishes a microscopic mechanism for pore condensation.