Multipolar capillary interactions: Self-assembly and Manipulation

Capillary interactions drive the aggregation of floating objects at fluid interfaces.
This thesis demonstrates that multipolar capillary interactions can be encoded purely through geometry, both within floating elements and across the liquid interface, to enable programmable complexity in mesoscale self-assembly and controlled micromanipulation.

A multipolar discrete-charge framework is developed to model anisotropic interface deformations and their interactions.
We first show that the tilt of a pinned contact line induces dipolar deformations that modify short-range attractions and extend pairwise interaction rules beyond linear superposition.
Saddle-shaped particles are then designed and modelled as quadrupolar elements, establishing explicit relations between geometry and orientation-dependent interaction potentials.

This geometric encoding is further extended to flexible chains of connected elements.
Energy landscape analysis demonstrates that the capillary sequence controls folded configurations and metastable states, providing a mesoscale analogue of molecular folding.

In a complementary approach, complexity is encoded at the interface level.
Arrays of 3D-printed spines generate curved liquid landscapes beyond the capillary length, enabling controlled particle guidance.
Dipolar Capillary Actuators introduce dynamic landscape reconfiguration, achieving trapping, directed transport, and non-reciprocal motion.