Endowed Distinguished Lecture in Fluid Mechanics

Sandra M. Troian, Ph.D.

“MicroAngelo Technique: 3D Sculpting of Nanofilms by Patterned Thermocapillary Forces For Micro-Optical Applications”

Event to be rescheduled


At age 17, with only a hammer and chisel, Michelangelo sculpted one of the most beautiful marble reliefs ever known, the Madonna of the Steps (1492). The submillimeter variations in thickness he was able to achieve by hand imbue this relief with a sublime, ethereal quality. Modern day electronic “sculpting tools”, such as extreme UV lithography, are also a marvel in their own right, now able to pattern films with feature sizes below 10 nm, although at considerable cost and requiring numerous processes steps. Between these two extremes now lies a number of newer patterning techniques ideally suited to feature sizes at the microscale. Though more and more popular, almost all such concepts or techniques are based on planar forms and due to etching processes, ultimately yield surfaces with considerable surface roughness. Here we explore the foundations and implementation of a new one-step, non-contact technique we have developed and coined MicroAngelo©, which is capable of shaping curved and even hierarchical structures having ultra-smooth surfaces. 3D sculpting of molten nanofilms is achieved by projection of patterned thermal fields which trigger thermocapillary forces that mold liquid into desired fluid shapes. Digital thermal control allows rapid cooling so that the structures can be affixed in-situ and used immediately. We’ll first review interesting theoretical aspects of this concept, which span topics such as linear and nonlinear stability, parametric resonance, self-similar cusp formation and self-focusing, pattern resolution limits and proximity correction for quenching undesirable nonlinear wave interactions. We’ll then review experimental efforts to measure the wavelength and growth rate of the fastest linearly unstable mode, as well as recent success in bypassing the linear instability to fabricate complex and hierarchical micro-optical arrays. In total, we hope our findings spur further development of a new class of lithographic tools generally based on programmable, patterned surface forces. Our efforts indicate that such tools will facilitate design and fabrication of next generation 3D micro-optical arrays and microfluidic circuits. 

Financial support from the NSF, NASA and NSTRF programs is gratefully acknowledged. 


PROF. SANDRA M. TROIAN directs the Laboratory of Interfacial & Small Scale Transport {LIS2T} in Applied Physics at the California institute of Technology in Pasadena, CA. She specializes in the fundamental science and engineering design of micro- and nanoscale liquidic systems. Her work focuses on identification and control of nonlinear wave phenomena involving the transfer of mass, momentum, heat and light along the surfaces of flowing films. Current projects include 3D design of micro-optical arrays by surface electrical and thermal modulation; Micro-propulsion and microfluidic technologies for space surveillance and planetary missions; Spreading of oil sheen after large ocean spills; and Marangoni phenomena pertinent to respiratory distress syndrome. Prof. Troian is also currently exploring breakdown in continuum based modeling of transport phenomena using molecular dynamics simulations. 

DR. TROIAN holds a B.A. in Physics from Harvard University (1980) and an M.S. (1984) and PhD in Physics (1987) from Cornell University. She is recipient of several awards including the François N. Frenkiel Award from the American Physical Society (1999), an Engineering Council Award for Excellence in Teaching from Princeton University (1999), a Moore Distinguished Scholar award from the California Institute of Technology (2004 – 05), American Physical Society Fellow (2005) and a Caltech ASCIT Teaching Award from the Academics and Research Committee (2009). Dr. Troian has also served on a number of editorial and advisory boards including the Defense Sciences Research Council, Annual Reviews of Fluid Mechanics, Physics of Fluids, the Kavli Institute for Theoretical Physics (Santa Barbara, CA), the Microdevices Laboratory of the NASA/Jet Propulsion Laboratory, the Max-Planck-Institut für Dynamik und Selbstorganisation and the Society of Engineering Science, Inc. She has also served as technical expert consultant to DARPA, SRI International and numerous biotech companies.

The Department of Chemical Engineering, part of the Herbert Wertheim College of Engineering, is one of the largest and highest ranked chemical engineering departments in the Southeast region and the premier chemical engineering department in the State of Florida. The department’s faculty and students conduct fundamental and applied research addressing important societal problems while advancing the discipline of chemical engineering in topics such as fluid mechanics, colloid and interface phenomena, biomolecular engineering, nanotechnology, advanced materials, catalysis, and surface science.


2019 Howard A. Stone Princeton University
2017 Harry Swinney University of Texas at Austin
2015 Grae Worster University of Cambridge