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.