Paddlebots: Translation of Rotating Colloidal Assemblies near an Air/Water Interface

Abstract

Microbot propulsion requires unique strategies due to the dominance of viscosity and the reversible nature of microscale flows. To address this, swimmers of specific structure that translate in bulk fluid are commonly used; however, another approach is to take advantage of the inherent asymmetry of liquid/solid surfaces for microbots (μbots) to walk or roll. Using this technique, we have previously demonstrated that superparamagnetic colloidal particles can be assembled into small μbots, which can quickly roll along solid surfaces. In an analogous approach, here we show that symmetry can be similarly broken near air/liquid interfaces and μbots propelled at rates comparable to those demonstrated for liquid/solid interfaces.

MicroTracker.jl: A Julia package for microbot research

“…Multiple publications that make use of tools in MicroTracker.jl are available, each unique in their scientific contribution and independent of this package. These include studies of microbots for use in the vasculature(C. J. , lungs(Coy J. , gastrointestinal system (Osmond et al, 2023), and at the air water interface (Wolvington et al, 2023).…”

Reversible Microwheel Translation Induced by Polymer Depletion

“…With advantages of in situ assembly and magnetic control, we have focused on using microwheels (μwheels) − where, upon application of a planar rotating magnetic field, micrometer-scale superparamagnetic beads reversibly assemble into disklike shapes that roll along available surfaces. Unlike conventional wheels that grip the surface, μwheels use wet friction to gain traction through a tens-of-nanometers scale fluid gap between the μwheel and the surface .…”