Droplet formation and regulation under microfluidic control
We analysed the operating principles for digital microfluidics regarding droplet generation, fusion and transport using immiscible fluids. For experimental evaluation several microreactors were fabricated in micromolded PDMS (polydimethylsiloxane) or bonded silicon to glass. The devices were prototyped and investigated for self-regulated two-phase container manipulation.
When two immiscible liquids (e.g. water and oil) are introduced to the microfluidic T-junction, a droplet phase flow can be obtained as a result of the high surface tension between the water-phase and the hydrophobic phase. We extended previous work in our lab and other groups to allow both continuous droplet generation as an artificial soft compartment and autonomously regulated serial droplet fusion (upper movie).
The formation of soft containers at defined locations, and the manipulation of their contents (e.g. fusion shown here) will allow chemical reactions to be performed in complex local volumes en route to the artificial cell.
Aqueous droplets in specific carrier fluids can easily obtained using the segmented-flow design (see above). We sought to extend these results to amphiphilic lipids, in order to later exploit their richer phase properties including vesicle formation, and make contact with the micellar protocell design. First experiments aiming at droplet generation of lipids in aqueous solutions remained unsuccessful in PDMS based microfluidic devices, but proved successful in silicon-glass microstructures [1].
REFERENCES
[1] P.F. Wagler, U. Tangen, M. Heymann, T. Maeke, S. Chemnitz, M. Juenger, T. Palutke, J.S. McCaskill in The Ninth International Conference on Miniaturized Systems for Chemistry and Life Sciences (μTAS), Boston, 2005, 1134-1136.