Encoding quadrupolar capillary information into saddle-shaped objects for self-assembly

Capillary-driven self-assembly at liquid interfaces, often illustrated by the ``Cheerios effect,'' has been limited to simple configurations. By introducing anisotropic, saddle-shaped particles, we demonstrate how quadrupolar capillary interactions can be encoded to achieve both end-to-end and side-by-side attraction; what we call the ``Pringles effect.'' Our theoretical model and experiments with 3D-printed objects reveal a versatile route to reprogrammable mesoscale assemblies, bridging capillarity and design for complex self-organization.