Impact of Enhanced Diffusion on Assembly Rate of Magnetic Janus Particles

Janus particles have anisotropic properties that can be exploited in microfluidic systems to enhance transport and mixing processes. Iron oxide-capped Janus particles create a magnetorheological fluid in water and have a dipole offset from their center, pointing tangent to the particle. The shifted dipole allows the application of a torque and control of the particle's orientation. In the presence of a magnetic field, the particles assemble into single-strand, parallel chains, i.e., so-called double chains. If there is a second, platinum cap covering the iron oxide cap and the particle is exposed to a hydrogen peroxide environment, the hydrogen peroxide decomposes on the platinum surface and the particle is propelled through the fluid. This "enhanced diffusion" results in a larger mean squared displacement and can lead to a higher rate of particle collisions and faster assembly. We have studied these systems with particle tracking software and are able to draw statistically significant conclusions about the behavior of autonomously moving magnetic Janus particles.