(163a) Janus Particles Swimming Along Solid and Liquid Boundaries

Janus particles are asymmetrical particles with different surface compositions on each hemisphere, giving each side a different surface property. The Janus particles in focus are silica particles half coated with platinum. When these particles are placed in a solution of hydrogen peroxide, the platinum reacts with the hydrogen peroxide and produces water and oxygen, which acts as a fuel to propel the particles forward in the solution. This self-motile, chemical motorized particle has potential applications for use in drug delivery, wastewater treatment, surface imaging techniques and sensors.

To fabricate these particles, monolayers of silica are place in a physical vapor deposition machine. Platinum is evaporated and deposited directly on top of the monolayers. During the deposition, the top of the silica particles acts as an umbrella, shielding the bottom half of the particles, rendering one side silica and the other side platinum. These Janus particles are then placed in a hydrogen peroxide solution and their trajectories are traced and quantified.

Next, the movement of Janus particles is observed around the perimeter of an oil droplet. A hexadecane oil droplet is pinned onto a glass slide using hydrophobic tape as an anchor. A larger Teflon ring is placed outside the perimeter of the oil droplet forming an observation cell. Then, a solution of water, hydrogen peroxide and Janus particles is pipetted inside the Teflon ring, creating a swimming basin around the oil droplet. The trajectories of Janus particles of different sizes are traced and compared as they swim along the oil droplet. Additional experiments with Janus particles of varying size are in progress to elucidate the effect of Janus particle size on its affinity to the oil-water interface.

Understanding the fundamentals of active colloid swimmers opens more opportunities for academic and industrial researchers to apply these devices to their work. Observing Janus particles’ behavior in different environments and on different types of boundaries, provides insight on how boundaries can be used to control Janus particles motility.