Surface entrapment of micromotors by a background temperature field

Abstract

The fabrication of self-propelling micromotors and the study of their propulsion strategies have gained attention due to their wide range of applications in the medical, engineering, and environmental fields. The role of a background temperature field in the precise navigation of a self-thermophoretic micromotor near an insulated wall has been investigated by employing exact solutions to the energy equation and creeping flow. We report bound states for half-coated micromotors appearing as steady-state sliding, damped, and periodic oscillations when the dimensionless external temperature gradient (S) is in the range of 0.15≤S<0.26. The sliding height is lower with S but remains insensitive to the thermal conductivity contrast. Moreover, the stationary states for the self-propelled, asymmetrically coated micromotors transform into scattering trajectories. We highlight the combinations of S and coating coverage needed for guided swimming up or against the field along with a broad spectrum of counter-intuitive temporal variations of its navigating locations. These unique observations have been ascribed to a confinement-mediated dynamic coupling between the passive and active propulsion mechanisms.