(713c) Exploring the Size Limit of Lateral Capillarity in Interfacial Assembly Processes

Capillarity-induced self-assembly behaviors at the air-water interface are critical to the design and fabrication of large-scale complex structures. Microscale and mesoscale particles with high horizontal-to-vertical aspect ratios have recently drawn attention as building blocks of self-assembled structures thanks to the well-defined curvature fields when they are pinned at fluidic interfaces. Nevertheless, the underlying kinetics of the lateral capillary interaction between particles at such length scales are still not thoroughly understood. Herein, we present an analytical model that quantifies the geometric, hydrophobic, and meniscus-undulation-induced attractive potential to describe the interfacial interactions between sub-millimeter disk-shaped micro-particles; we systematically reduce the horizontal and vertical dimensions of the micro-disks and experimentally probe the predictive Bond number limit of the classical two-dimensional theoretical treatment for lateral capillarity, and demonstrate the geometric and hydrophobic regimes where attractive interactions that stem from topographical fluctuation-induced meniscus undulations can no-longer be ignored. These insights are important for guiding system design as researchers steadily downscale the dimensions of constitutive parts and leverage lateral capillarity for materials assembly at fluidic interfaces.