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 sieving curve. Estimated longest crystal dimension: 24 hours sieving curve. 48 hours sieving curve.
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: 24 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 resistance is larger than the transmembrane (steric/frictional) resistance for small molecule sizes. The total resistance…
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 Bill Bernhard, although their results were due to a salt imbalance if I recall correctly….
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 measurements seem to follow the same trend, although the EO is lower in all cases….
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 each of the active areas shown here. Obviously if we were to publish this we’d…
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 (original figure bottom of this post). In this figure we show flow rate normalized to…
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). In essence, the equation for streaming potential (E) becomes: where , P is the applied…
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 of electroosmosis is dependent on the electric field across the material and the zeta potential….
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). The second is due to the time that it takes for the molecule to diffuse…