Janus particles at an oil-water interface

We study the behaviour of Janus particles at an oil-water interface. Amphiphilic Janus particles exhibit attractive interactions at the fluid-fluid interface. The attractive interactions are likely due to the pinning of contact line around the diffuse boundary between the two hemispheres. The undulation of the three-phase contact line around Janus particles leads to quadrupolar capillary interactions, which we confirm by measuring the interparticle forces. We also show that Janus particles with two negatively charged-hydrophilic hemispheres show repulsive interactions.