SUBJECT: Ph.D. Proposal Presentation
BY: James Black
TIME: Wednesday, February 29, 2012, 4:00 p.m.
PLACE: Love Building, 109
TITLE: Compound Droplets for Lab-On-A-Chip
COMMITTEE: Dr. G. Paul Neitzel, Chair (ME)
Dr. G. P. "Bud" Peterson (ME)
Dr. Marc K. Smith (ME)
Dr. Michael Schatz (PHYS)
Dr. David Quéré (ESPCI ParisTech)


The development of a novel method of droplet levitation to be employed in lab-on-a-chip (LOC) applications relies upon the mechanism of thermocapillary convection (due to the temperature dependence of surface tension) to drive a layer of lubricating gas between droplet and substrate. The fact that most droplets of interest in LOC applications are aqueous in nature, coupled with the fact that success in effecting thermocapillary transport in aqueous solutions has been limited, has led to the development of a technique for the controlled encapsulation of water droplets within a shell of inert silicone oil. These droplets can then be transported, virtually frictionlessly, resulting in ease of transport due to the lack of friction as well as improvements in sample cross-contamination prevention for multiple-use chips. Previous reports suggest that levitation of spherical O(nL)-volume droplets requires squeezing to increase the apparent contact area over which the pressure in the lubricating layer can act allowing sufficient opposition to gravity. The proposed research is designed to explore thermocapillary levitation of O(nL)-volume single-phase oil droplets and O(nL)-volume oil-encapsulated water droplets as well as show how the vigorous internal thermocapillary convection can aid in droplet mixing if two levitated samples are allowed to coalesce, an added benefit to LOC processes.