Collaborative Research: The Role of Monolayer Structure on Interfacial Hydrodynamics

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ABSTRACTPROPOSAL NO.: CTS-0340768 AND 0340736PRINCIPAL INVESTIGATORS: AMIR H. HIRSA AND JUAN M. LOPEZINSTITUTION: RENSSELAER POLYTECHNIC INST./ARIZONA STATE UNIVERSITY THE ROLE OF MONOLAYER STRUCTURE ON INTERFACIAL HYDRODYNAMICSThe goal of this research program is to advance fundamental understanding of surfactant monolayer hydrodynamics. Applications of monolayer hydrodynamics are numerous. Technology examples include material and food processing, liquid atomization, and coating systems. An example of a natural system dominated by monolayer hydrodynamics is the lung. In the absence of surfactant monolayers, the surface tension of the aqueous film covering the lung tissue would close the passages and make respiration impossible. This research is intended to provide fundamental insight into the nature of interfacial hydrodynamics by developing new theories, and numerical and experimental techniques to test these theories. In particular, the role of monolayer mesoscale structure on interfacial transport processes will be elucidated, as will the effect of flow on the monolayer structure. Use of simple constitutive relations in interpreting experimental data in the past has led to the conclusion that many monolayers have an apparent negative surface dilatational viscosity. This is not physically consistent with the second law of thermodynamics. In this project, contributions from non-equilibrium monolayer concentration and phase morphology will be considered, and these may provide an explanation for the observed enigma of apparent negative surface dilatational viscosity. This issue is of fundamental significance and will have a broad impact on a wide range of fields as the drive to miniaturization leads to small-scale open fluidic systems in which the viscous contributions to the interfacial stresses dominate over the elastic contributions. Better understanding of monolayers is expected to have a significant impact on the industrial and biomedical communities working on designer surfactant monolayers. Also, the multidisciplinary nature of this project will provide an excellent opportunity to educate graduate and undergraduate students in both science and engineering.*co-funded jointly by the Fluid Dynamics & Hydraulics, and Interfacial, Transport and Thermodynamics programs, and Math Sciences Priority Area.