Capillary-driven Interactions at Solid and Liquid Interfaces: Adhesion, Bridging, and Removal

Capillarity governs how fluids interact with interfaces, linking fundamental physics with engineering applications. Although the thermodynamics based on surface tension and Laplace pressure are well established, how these interactions evolve across scales and physical environments remains incompletely understood. In this thesis, I investigate three core aspects of interfacial capillarity: particle adhesion, liquid bridging, and capillary-driven droplet removal, aiming to develop a unified framework that connects microscopic interactions to macroscopic function through integrated experiments and quasi-static modelling.

Starting from the nanoscale, particle adhesion at liquid interfaces is quantified using atomic force microscopy and modelling. The results show that classical thermodynamics remains valid, with adhesion governed by geometry and wettability, while line tension becomes significant below a characteristic length threshold. This insight supports the design of functional nanoparticles that either resist or promote interfacial adsorption. At millimetre scales, I examine capillary bridges across hydrophilic, hydrophobic, and liquid-infused surfaces. Distinct contact line dynamics are revealed, from pinning and hysteresis on solid surfaces to near-frictionless motion on liquid-infused surfaces, yet all systems can be consistently described by interfacial tension and Laplace pressure. On liquid-infused surfaces, enhanced mobility enables lubricant transfer and amplifies gravity-induced geometric asymmetry, providing design strategies for controlled capillary–substrate interactions.

Building on these insights, I introduce a capillary-lifting mechanism for efficient droplet removal. By harnessing high interfacial tension as the driving force for detachment, this approach eliminates the need for surfactants and reduces water consumption. Predictive detachment criteria based on apparent and receding contact angles are validated through agreement between experiments, simulations, and theory. The method is further demonstrated using real-world contaminants and low-additive formulations, highlighting its potential for sustainable cleaning.

Together, this thesis establishes a predictive and experimentally validated framework for capillary behaviour from nanometre to millimetre scales, advancing our understanding of how interfacial geometry and chemistry govern capillary forces and liquid morphology. More importantly, this work demonstrates how subtle yet powerful interfacial capillarity can be harnessed to control solid–liquid interactions, direct droplet motion, and achieve efficient liquid removal, opening new opportunities in liquid manipulation, functional materials, and sustainable surface technologies.