(312a) Microscale Engineering of Responsive, Flexible and Reconfigurable Particle Structures

We will discuss the principles of microscale engineering of novel classes of flexible and dynamically reconfigurable assemblies from colloidal particles. Examples of such assemblies include magnetically reconfigurable gel networks, shape-changing microbots, and inks for 3D printing. The key to making such structures is the engineering of directional interactions and of flexible inter-particle bonds. In the first part of the talk, we will discuss how complex magnetic polarization patterns on metallo-dielectric microcubes lead to multidirectional interactions and assembly of reconfigurable microclusters. These sequence-encoded clusters can be reversibly actuated and spatially transported by magnetic fields and can be designed to be self-motile in non-Newtonian media. In the second part of the talk we will describe new types of multiphasic capillary gels from particles bound by liquid bridges. The first gel system is made of filaments from magnetically responsive iron oxide nanoparticles suspended in water-oil systems. The nanocapillary binding results in ultra-high filament flexibility. The second multiphasic system that we introduced is a new class of 3D printing inks consisting of PDMS microbeads, liquid PDMS and water. Owing to the capillary binding, such Homocomposite Thixotropic Pastes (HTPs) can be extruded and shaped on a 3D printer. The curing of the liquid bridges in the HTPs results in remarkably elastic and flexible porous silicone materials, which can be 3D printed under water and find applications such as direct printing of bio-scaffolds.