We present a microfluidic platform for the generation, characterization and optical manipulation of monodisperse oil droplets in water with equilibrium interfacial tensions on the order of 0.1-1μN/m. An oil-in-water emulsion containing the surfactant Aerosol OT, heptane, water and sodium chloride under conditions close to the microemulsion phase transition was used. Through active control of the emulsion salinity and temperature, our microfluidic platform offers the unique capability of tuning the interfacial tension of droplets in the range of 1μN/m to few mN/m according to the operation required. Upon collection in a separate observation chamber, droplets were characterized by using video microscopy-based measurement of thermally-induced capillary waves at the droplet interface. Holographic optical tweezers were used to manipulate the droplets and construct 3D nanofluidic networks consisting of several droplets connected by stable oil threads a few nanometers across.

Date Published: 1 June 2015
PDF: 11 pages
Proc. SPIE 9520, Integrated Photonics: Materials, Devices, and Applications III, 95200B (1 June 2015); doi: 10.1117/12.2178964

Published in SPIE Proceedings Vol. 9520:
Integrated Photonics: Materials, Devices, and Applications III
Jean-Marc Fédéli, Editor(s)