(221a) Janus Spheres At a Fluid-Fluid Interface

Janus spheres are asymmetric particles with polar and apolar hemispheres. In this work, we study the interactions and assembly of Janus spheres – bubbles and solid particles – at a fluid-fluid interface.  Janus spheres are prepared using the selective deposition of gold onto one hemisphere of a monolayer of spheres.  Ultra-stable bubbles that can withstand drying are used for the Janus bubble preparation.  These bubbles are prepared using air-in-oil-in-water compound bubbles as templates, which allow for the control of bubble dimensions.  Both the Janus bubbles and the Janus particles have strikingly different interfacial behaviour compared to their homogeneous counterparts.  Janus spheres at a fluid-fluid interface interact with one another via long-ranged attractions. We show that the attractive interactions between interface-trapped Janus spheres are induced by the presence of diffuse boundary between the two hemispheres. Three phase contact line anchored around the rugged Janus boundary deforms that the fluid interface leading to attractive interactions between the spheres.  The orientation and fluid deformation caused by Janus spheres are directly observed using a gel trapping method.  We also show that the surface chemistry of Janus spheres plays a critical role in determining their interfacial behaviour.