We will discuss the principles of microscale engineering of dynamically reconfigurable and motile assemblies from multiple classes of colloidal particles. Examples of such assemblies include reconfigurable gel networks, shape-changing clusters, and self-propelling microbots. The making of such structures requires techniques for creating flexible bonds and directing particle-field and particle-particle interactions. In the first part of the talk, we will present magnetically-responsive and self-repairing gel networks and inks for 3D printing based on multiphasic liquid/liquid/solid systems. These are made of superparamagnetic nanoparticles dispersed in water, magnetically assembled into filaments, and bound by nanocapillary liquid bridges. The capillary binding allows for easy particle rolling and sliding, resulting in ultra-high filament flexibility and responsiveness. In the second part of the talk we will describe 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. They can be designed to be self-motile in media with non-Newtonian rheology. We analyze the propulsion dynamics of these active clusters based on a "coupled scallop" model and showcase their ability to grab and transport target micro-objects, hence serving as prototypes of microbots and colloidal origami. Finally, we will describe how electric fields can be used to introduce further levels of functionality in powering and controlling motile circuit-containing particles of complex shape, structure, and internally programmed response.

Field-driven assembly, manipulation, and propulsion of dynamic structures made of particles

256th National Meeting (2018)

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