To: 02/10/2023 18:00
The use of magnetic fields is one of the most efficient means of assembling colloidal structures and manipulating their structure, interactions, and dynamics. More recently, it has become a convenient means of powering and controlling active colloidal structures and microbot prototypes. This talk will discuss a few classes of dynamically reconfigurable, active, and self-propelling magnetic colloidal structures. We will first discuss how the combination of magnetic assembly and nanocapillary liquid binding can be used to make ultraflexibile and responsive filaments from lipid-coated nanoparticles suspended in water. Alternatively, the nanoparticle chains can be assembled and embedded inside silicone microbeads, resulting in a few types of soft micromagnets and microvoxels. These soft magnets can be incorporated into homocomposite thixotropic silicone pastes and can be directly shaped on a 3D printer to enable multiple classes of active magnetically reconfigurable structures. In the second part of the talk, we will discuss the principles of using magnetic assembly and actuation of dynamically reconfigurable active particle structures. We will show how assemblies of Janus polymer-metal microcubes can store energy through magnetic polarization of the metallic facets and release it on-demand by microscale reconfiguration. The reconfiguration pattern of folding and shape changes of the assemblies is encoded in the sequence of the cube orientation. Such structures can be directionally moved, steered, and maneuvered by external magnetic fields, acting as prototypes of microbots, micromixers and other active microstructures. These reconfigurable clusters can also be designed to be self-motile in media with non-Newtonian rheology. Such active assembles can serve as microtools for interfacial studies in liquid crystal and biological systems.