Capillary-assisted printing of droplets at a solid-like liquid-liquid interface

The droplets could be placed at the solid-like oil-water interface for extended periods of time. Microlitre-sized droplets attracted each other over millimetric scales. System dynamics differed from theoretical predictions for pristine interfaces and were captured by a simple model. This inter-droplet capillary attraction facilitated the printing of self-building droplet structures. Embedding gold nanoparticles in the NPS assembly allowed us to generate local temperature gradients by illuminating the system with a laser and manipulate the droplets via plasmon-assisted optofluidics.