Single Janus particles in a complex plasma environment

Abstract

In the present work a never explored field is experimentally investigated: active particles in a complex plasma environment. Janus particles belong to a special category of particles that are active in aqueous solutions because of their intrinsic asymmetry. The aim is to discover if they are also active when suspended in a low-temperature weakly-ionized plasma. The forces which can potentially act as propulsion mechanisms in a plasma environment are investigated both theoretically and experimentally. The Janus particles used are 9.27 um diameter melamine-formaldehyde spheres half covered with 10 nm of platinum. The result of the present work is that they are active in a complex plasma environment. The propulsion mechanism is the thermophoresis due to different accommodation coefficients on the particle surface in case non-strong light source is used. In the case a laser light is used to illuminate the Janus particle, the net force acting on the particle as self-propulsion is due to a combination of thermophoresis due to different accommodation coefficients, photophoresis due to a temperature gradient on the particle surface and alternating radiation pressure force.