  We demonstrate the realization of (laterally) optically bounded colloidal
structures on a liquid-liquid interface of an emulsion droplet. We use DNA
tethers to graft the particles to the droplet surface, effectively confining
them to a quasi-2D plane with minimum constraints on the lateral movement even
when optically trapped in a common single-beam configuration. We show that
relatively weak interactions such as depletion can be measured in the optically
bounded crystals by video-microscopy imaging and analysis. This illustrates the
possible use of our system as template to study optically controlled quasi
two-dimensional colloidal assembly on liquid-liquid interfaces.
