(151h) Self-Assembly of Thermoresponsive Colloidal Clusters of Patchy Particles Via Capillary Binding

Authors: 
Bharti, B., North Carolina State University
Rutkowski, D. M., North Carolina State University
Hall, C. K., North Carolina State University
Velev, O. D., North Carolina State University
Janus and patchy particles are emerging as models for studying complex directed assembly patterns and as precursors of new structured materials and composites. Here, we introduce lipid induced capillary bridging as a new and nonâ??conventional method of assembling patchy particles into ordered structures. We used the selective wetting of iron oxide surface patches on latex microspheres to drive the patchy microsphere assembly into 2D and 3D clusters via interparticle capillary bridge formation. The liquid nature of the bridges allows local reorganization of the particles within the clusters and assists in forming true equilibrium configurations. The temperature driven fluid-to-gel and gel-to-fluid phase transition of the fatty acids within the bridge acts as a thermal switch for cluster assembly and disassembly. By comparing our experimental data to Monte-Carlo simulations we show that the equilibrium cluster morphology is determined by the patch size, number, and shape. The results demonstrate the ability of capillary bridging as a unique tool to assemble thermoresponsive clusters and aggregates. This simple method of binding particles is very robust and generic, and it can be extended further to assemble particles with non-spherical shapes and complex surface chemistries leading to the realization of colloidal clusters of sophisticated structure.