Professor Chemical Engineering CCNYAreas of Expertise:
Interfacial and biomembrance phenomena: fluid mechanics and hydrodynamic stability; visoelasticity.
EducationB.S.(Ch.E.), 1976, M.S.(Ch.E.), 1978, D.Eng.Sc., 1980, Columbia University
Career HighlightsIn the area of multiphase flows in capillaries, our group is studying two periodic flow regimes experimentally and theoretically. The first is the two-phase motion of wetting liquid lenes separated by gas segments; the second is the three-phase motion of an alternating train of gas and liquid segments moving over an annular film of a wetting liquid. Our experimental objectives are to measure the pressure drop required to move the segmented stream and the thickness of the annular wetting film present on the inside surface of the capillary. Theoretically we are developing numerical and analytical asmptotic solutions for the pressure drops, film thicknesses and interfacial shapes realized.
Investigations of mass transfer from fluid droplets moving in a continuous liquid phase focus on the influence of adsorbed surfactant monolayers on the rate of interphase transfer. When surfactants adsorb onto the surface of a moving droplet, the surfactant molecules are convected to the trailing pole of the droplet where they form a compressed monolayer. The question of interest to us is how this monolayer affects mass transfer of solute molecules from the drop to the exterior phase. Evidence exists that the compressed monolayer offers an obstruction to interphase transfer. Thus solute molecules which diffuse from the droplet into the continuous phase must diffuse around the layer. This circumvention significantly reduces the rate of transfer. Currently we are attempting to solve the mixed boundary value problem to predict the extent of reduction as a function of the interfacial properties of the adsorbing surfactants. Thin film instability problems which we are studying include Marangoni driven instabilities in a viscoelastic film and capillary and viscosity stratification induced instabilities in annular wetting films. With respect to the Marangoni instabilities, our research focuses on how the film's viscoelastic properties influence its oscillatory instability states.
Chemo-mechanical mechanisms can explain how chemical reactions can cause biomembrane deformations. One mechanism which we have suggested postulates that chemical transformations of molecules present on the surfaces of biomembranes cause local changes in the surface area of one face of the membrane. Examples include transconformational reactions of proteins and antigen-antibody complexing. Such differential area changes induce bending moments which can deform the membrane. We have developed bending equations which account for this mechanism and are now using nonlinear stability theory to develop expressions for the membrane deformation patterns as a function of adopted chemical kinetic schemes.
BooksDekker Encyclopedia of Nanoscience and Nanotechnology
Important ArticlesIsland Surfaces: Fabrication
By this Researcher