(485f) Influence of Interfacial Forces on the Propulsion of Active Colloids

Active colloidal particles regularly interact with surfaces in applications ranging from microfluidics to sensing. Recent work has revealed the complex nature of these surface interactions for active particles. Our work is focused on the prediction and measurement of how the properties of a nearby interface influences the propulsion of an active particle. This talk will summarize experiments and simulations that show the impact of nanoparticles on the propulsion of an active colloid near a boundary. We found that adding charged nanoparticles decreased the apparent propulsion of a Janus colloid to near zero. Complementary agent-based simulations considering the impact of hydrodynamics for active Janus colloids were conducted in the range of separation distances inferred from experiment. These simulations showed that propulsion speed decreased monotonically with decreasing average separation distance. Although the trend found in experiments and simulations were in qualitative agreement, there was still a significant difference in the magnitude of speed reduction. The quantitative difference was attributed to the influence of charged nanoparticles on the conductivity of the active particle suspension. This talk will also discuss preliminary work on the interactions of active particles with nearby fluid - fluid interfaces.