Applied Physics at Caltech

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Dr. Sandra M. Troian

Professor of Applied Physics, Aeronautics and Mechanical Engineering; Option Representative for Applied Physics

154 Watson
MC 128-95
(626) 395-3362

B.A. - Harvard University, 1980
M.S. - Cornell University, 1984
Ph.D. - Cornell University, 1987

Troian Research Group

Expertise

Micro/nano transport phenomena in liquid films and interfaces including confinement effects, pattern formation, instabilities and phase transitions; biological flows subject to Marangoni stresses; tunable microfluidic and optofluidic devices based on electrical, thermal or acoustic fields; lithographic patterning by thermocapillary or electrohydrodynamic forces.

Field of Study

The Troian group investigates micro- and nanoscale transport phenomena in liquid films and interfaces as occur in many biological, physical and materials-based flows. The flow of mass, momentum and energy in ultra small structures which manifest large surface to volume ratios is highly responsive to interfacial stresses. Such stresses can be generated internally or externally through gradients in electrostatic, thermal, pressure (acoustic) or concentration fields. Nearby solid boundaries can also be modified to influence flow behavior by using modern lithographic techniques for generating substrates with surface energy gradients, complex topologies, and varying adhesion or friction reduction. By tuning normal and tangential stresses at fluid/fluid and fluid/solid interfaces, it is possible to control the flow and response of small liquid-like elements in space and time. Currently, the group is focusing on shape changes, flow instabilities and phase transitions triggered by inhomogeneous force fields. In several systems of interest, infinitesimal disturbances which elicit maximum growth tend to be highly non-normal. To probe these phenomena at several lengthscales, we use a combination of experiment, first principles modeling, and molecular level or hydrodynamic simulations.

Current research projects include:

Biological flows triggered by Marangoni and capillary forces

Interfacial instabilities driven by non-normal disturbances

Characterization of dynamic friction and slip at liquid/solid interfaces

Microfluidics with electrowetting, dielectrophoresis or thermocapillary forces

Confinement effects, layering transitions and instabilities in nanofilms

Evanescent wave based sensors for micro/optofluidic devices

Transport of lipids in nanotubes, vesicles and membranes

Dynamics of free surface films on topologically modified sustrates

Pattern replication by thermolithography in nanoscale polymer films

Special Links

Troian Research Group

images this page:

Top: Interferometric image of an instability triggered by surfactant transport on a 10 µm aqueous film.

Bottom: Microfluidic chip based on thermocapillary actuation. Embedded arrays of Ti microheaters are used to generate thermal surface maps for moving, mixing, splitting and reacting liquid droplets.

last modified 25 February, 2008
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