Microparticle Propulsion for in vivo Navigation

Microscale propulsion impacts a diverse array of fields, with simplistic microrobots allowing for novel innovations in microscale surgery and drug delivery. Propulsion at the microscale is constrained by physics, with time-reversal and geometric symmetries limiting available propulsion mechanisms. However, certain fluid environments and surface coatings allow for the propulsion of microparticles through externally applied magnetic fields. Presented here is a detailed analysis of microparticles propelling using spontaneous symmetry breaking, flagella surface coatings, and multi-modal actuation mechanisms. Spontaneous symmetry breaking in nonlinearly viscoelastic fluids is presented for the first time in literature, with two equal and opposite propulsion states existing along a microparticles rotation axis. Flagellated microparticles suspended in Newtonian fluids are demonstrated to have diverse behavior in response to rotating magnetic field frequency and direction. Finally, catalytic Janus particles were developed which could exhibit catalytic propulsion and swimming propulsion interchangeably. The continued exploration of these propulsion mechanisms will be used to further circumvent restrictions on propulsion, helping to revise notions of microrobotic design and control, drug delivery, microscale pumping, and locomotion of microorganisms