(647b) Controlling Active Particle Dynamics at Lipid Bilayer Interfaces

In this talk, we discuss the development of an active colloidal system with controllable interactions with an artificial lipid bilayer membrane as a model for investigating the interplay of membrane mechanics and the transport of particles during adhesion and wrapping. We use polystyrene microspheres coated with a hemispherical platinum cap as particles whose active motion is initiated by hydrogen peroxide addition. Two classes of particle-membrane interactions and particle swimming direction are assessed. For the former, carboxylated particles are used to passively interact with the membrane through electrostatic interactions, while neutravidin coated particles are used with biotinylated lipid membranes for bound particles. Active particles are designed to be “pushers”, which swim toward their metal face into the bilayer, or “pullers”, which swim away from the membrane. We find that gravitaxis causes the steady movement of unbound pullers away from the membrane with increasing H₂O₂. When the particles are bound, a threshold H₂O₂ concentration is needed before overcoming the strength of the biotin-neutravidin bond and releasing the particles from the interface. For the puller system, as the H2O2 concentration increases the particles become increasingly wrapped in the membrane. We monitor their translational and rotational dynamics and apply active Brownian models to characterize the nature of the particle-membrane interactions and also particle pair interactions. These results show promise for the potential to combine active colloidal systems with model lipid membranes to understand active transport in cellular contexts.