UPDATE: A look at long and short crystal dimensions (9/1/10): DLS vs. Crystal Sizes – Newest version 8/30/10 Here is a comparison of sieving curves using DLS or estimated crystal dimensions of proteins. DLS: 24 hours sieving curve. 48 hours…

These are cross sections of my comsol diffusion model.  Each chip has 6 square wells terminated in a membrane.  This cross section cuts across the two middle wells.  Concentration contours are in 0.025 intervals. 6 hours: 12 hours: 18 hours:…

This figure is a potential response to Reviewer’s 1 question about the difference between pore discovery and transmembrane resistances and Reviewer’s 2 question about membrane vs. well resistance. a.  Resistances for an ultrathin membrane with large pores.  The pore discovery…

One of the reviewers for the diffusion based separations paper was concerned that there would be osmotic pressure which would cause convection across the membrane.  Previously we have been aware of osmosis in the DNA experiments by Paul Black and…

You can use any electrokinetic phenomena to determine zeta potential since they’re all related.  Here I’ve determined the zeta potential of untreated (non), plasma oxidized (ox), and silanized (asi) samples using both streaming potential measurements and electroosmotic flow rates. These…

I dug out some of my old data and found this comparison for 3x and 6x window flow rates at different voltages (minimal repeats, error bars not included): This shows that as voltage goes up, the flow rate increases for…

Pnc-Si membranes have a high rate of EO pumping, but what is the best way to compare to other pumps?  The initial figure we used is an updated version of a figure found in a paper about alumina EO pumps…

Narrow pore EO theory In narrow pores that have a significant Debye length, we need to use the same corrections on surface potential in streaming potential theory that we used in electroosmosis theory (click on link above for EO theory).…

During my previous derivations of electroosmotic theory, I described the electroosmotic velocity using the classical Helmholtz-Smoluchowski equation: where ε is the permittivity, E the electric field, ζ the zeta potential, and η the viscosity.  This equations basically says the velocity…

In the soon to be submitted paper on diffusion models, we list two contributions to membrane resistance.  The first is due to the steric and frictional hindrance a molecule encounters as it enters and diffuses through a pore (Renkin, Deen).…