Programmable Assembly of Responsive Capillary Multipoles

The ability to program inter-particle interactions with well-defined selectivity, directionality, strength, and range remains a central challenge in efforts to realize complex materials by self-assembly of simple building blocks. Capillary attraction or repulsion owing to the geometrical distortion of the three-phase contact line by non-spherical particles has emerged as a powerful means to program two-dimensional assembly. To date, however, the focus has been almost exclusively on assembling rigid particles having shapes of limited complexity, restricting both the types of assemblies and their reconfigurability. We take advantage of the stimuli-responsiveness and the low-energy bending deformation of hydrogel particles, to show stimulus-controlled modulation of shape-induced capillary assembly. We anticipate that such surface tension-driven modification of the capillary interaction will suggest a rich area for fundamental studies and opportunities to further tailor the inter-particle interactions.