Three Types of Condensation in Open Wedges

We investigate capillary condensation in open wedges formed by two nonparallel walls of finite length connected to a bulk gas reservoir. In contrast to infinitely long wedges, where filling occurs continuously, condensation in open wedges is always first-order and exhibits remarkably rich phase behavior controlled by the wedge opening angle, aspect ratio, and Young contact angle. Using a macroscopic thermodynamic description based on meniscus geometry and free-energy minimization, we identify three distinct condensation states: single-pinning (SP), semi-double-pinning (SDP), and double-pinning (DP). These states differ in the configuration and pinning of the menisci separating the condensed liquid from the surrounding gas. We derive Kelvin-like equations governing each condensation regime, determine the conditions for transitions between them, and construct global phase diagrams revealing reentrant behavior and continuous higher-order depinning transitions between condensation states. The analysis further provides asymptotic scaling laws in several important limits, including narrow wedges, very long systems, and the approach to the condensation threshold.

• J. Janek, A. Malijevský: Three Types of Condensation in Open Wedges. Phys. Rev. E 111, 045507, 2025. DOI