Focused Project: High-throughput measurement of interfacial
tension
Introduction
Interfacial tension: an important
property of formulations
Based on NCMC member interest, this project was initiated in
Sept. 2003. Properties of interest
Efficacy of surfactant, e.g., for detergency or emulsification.
Equilibrium and dynamic tension
Surfactant sorption isotherm and dynamics. Strategy
Microfluidics and real-time automated image analysis. Objectives
Develop a high-throughput measurement technique for interfacial
tension in polymer formulations.
s ranging from 0.1 to 70 mN/m.
Few percent accuracy.
Focus on systems: Oil/water/air/surfactant/ cosurfactants/other
additives, e.g., viscosifiers.
Efficiently measure a range of compositions.
Also, integrate with materials synthesis and/or other measurements.
Experimental
Real-time image analysis: directly measures: Drop position,
speed, size and deformation, fluid extension rate, with over
100 data points / s
Determine s, knowing hd, hc
Droplet formation and deformation in microfluidics.
Experimental setup
LabVIEW interface
Results
Microfluidic devices are designed
to include droplet formation, mixing, acceleration and deformation
stations. They are fabricated using contact photolithography
and PDMS elastomer replication
A model system of water/oil mixtures
with and without added surfactant (here a Pluronic P65) is investigated
This microfluidic system obtains measurements in several
seconds and is accurate within a few percent.
The instrument design is amenable to efficient adjustment
of formulation composition.
Water in oil mixtures
Rapid device prototyping
Devices are fabricated using UV frontal photo-polymerization
(FPP) contact lithography followed by PDMS replication and sealing.
Light exposure modulation yields complex 3-D structures.
Publications
“Microfluidic analogue of the 4-roll mill” S. D.
Hudson, F. R. Phelan, Jr., M. D. Handler, J. T. Cabral, K. B.
Migler, E. J. Amis, Appl. Phys. Lett., in press.
“Frontal Photopolymerization for Microfluidic Applications,”
J. T. Cabral, S. D. Hudson, C. Harrison, J. F. Douglas, Langmuir,
in press.
“A rapid prototyping technique for the fabrication of solvent-resistant
structures” C. Harrison, J. T. Cabral, C. M. Stafford,
A. Karim and E. J. Amis J. Micromech. Microeng. 14 (2004) 153–158.
“Measuring interfacial tension in microfluidics” S.
D. Hudson et al. in preparation.
Sponsored by:
Combinatorial Methods Group
Polymers Division
Materials Science and Engineering Laboratory
