Date: Tuesday, January 31, 2012. 4:00 PM.
Location: Bldg. 300 Room 300
Stanford Fluid Mechanics Seminar (E298) Tuesday, January 31, 2012 4:15pm – Building 300, Room 300 Prof. Hsueh-Chia Chang Dept. of Chemical & Biomolecular Eng., Notre Dame Univ. Micro-Vortex "Turbulence" and Other Anomalous Electrikinetic Dynamics due to Non-equilibrium Ion Transport Across Ion-Selective Membranes and Nanopores Intra-pore and external electrolyte depletion/enrichment of an ion-selective medium, like a charged nanoporous membrane or a single synthetic nanopore, by a transverse electric field is shown theoretically and experimentally to be responsible for many non-linear ion-current dynamics like rectification, excitability, hysteresis, oscillation and self-similar fluctuations, which cannot be described by Onsager-type near-equilibrium ion transport theory. Mixed electro-osmotic/pressure-driven flow through the medium, in particular, is shown to be responsible for ion current oscillations and fluctuations in weakly selective media under asymmetric driving forces that are theoretically delineated. External depletion at high voltages can produce an extended surface charge layer, which suffers from an electrical version of the Rayleigh-Taylor vortex instability that leads to a period-doubling (vortex pairing) cascade to broadbanded two-dimensional vortex turbulence at a small diffusion layer near the membrane surface/pore entrance. Analogous to shear-flow turbulence, localized vortex injection events are observed at surface polarization singularities, which interact with each other dynamically like coherent structures, and the infra-red cutoff of the self-similar power spectrum is determined by viscous dissipation at the boundaries. While these nonlinear ion current dynamics originate from mechanisms different from their protein ion channel counterparts on biological cell membranes, we show how they can still be exploited for biosensing and molecular delivery applications. Hosted by: Ali Mani, Professor Mechanical Engineering, alimani@stanford.edu Refreshments served starting 4PM.
Location: Bldg. 300 Room 300
Stanford Fluid Mechanics Seminar (E298) Tuesday, January 31, 2012 4:15pm – Building 300, Room 300 Prof. Hsueh-Chia Chang Dept. of Chemical & Biomolecular Eng., Notre Dame Univ. Micro-Vortex "Turbulence" and Other Anomalous Electrikinetic Dynamics due to Non-equilibrium Ion Transport Across Ion-Selective Membranes and Nanopores Intra-pore and external electrolyte depletion/enrichment of an ion-selective medium, like a charged nanoporous membrane or a single synthetic nanopore, by a transverse electric field is shown theoretically and experimentally to be responsible for many non-linear ion-current dynamics like rectification, excitability, hysteresis, oscillation and self-similar fluctuations, which cannot be described by Onsager-type near-equilibrium ion transport theory. Mixed electro-osmotic/pressure-driven flow through the medium, in particular, is shown to be responsible for ion current oscillations and fluctuations in weakly selective media under asymmetric driving forces that are theoretically delineated. External depletion at high voltages can produce an extended surface charge layer, which suffers from an electrical version of the Rayleigh-Taylor vortex instability that leads to a period-doubling (vortex pairing) cascade to broadbanded two-dimensional vortex turbulence at a small diffusion layer near the membrane surface/pore entrance. Analogous to shear-flow turbulence, localized vortex injection events are observed at surface polarization singularities, which interact with each other dynamically like coherent structures, and the infra-red cutoff of the self-similar power spectrum is determined by viscous dissipation at the boundaries. While these nonlinear ion current dynamics originate from mechanisms different from their protein ion channel counterparts on biological cell membranes, we show how they can still be exploited for biosensing and molecular delivery applications. Hosted by: Ali Mani, Professor Mechanical Engineering, alimani@stanford.edu Refreshments served starting 4PM.