In an attempt to address the Nano Letters reviewer’s comment (show molecular separation, not just Au), I ran a simple experiment where I tried to pass BSA, Cyt. C, IgG, and β-galactosidase through carbonized membranes in the pressure cell. We have to be careful in calling this a “separation” since the two different species were never…
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…
Last week, I calculated the Young’s modulus and residual stress of several different membranes using the pressure-displacement technique. The measurements were performed on at least three different geometries (square and rectangle) and the results were averaged. Wafer Thick. (nm) Por. (%) Anneal Res. Stress (MPa) Young’s modulus (GPa) 532 15 2.59 1000 sus 4.17 31.67…
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…
I had some extra samples from last week and had been wanting to try SEM on cells, so I went for it this week. Specifically, I was hoping to get images of vacuoles in cells over free-standing pnc-Si. I followed a rather complicated protocol full of dangerous chemicals to fix the cells and then dehydrate…
I’ve been working recently with amyloid-beta (AB) provided to me by some people in Brad Nilsson’s lab. These experiments are related to the HMM diffusion experiments for our collaboration with Harold Smith. Basically, AB fibrils are very long (microns) and we are looking for ways to either prevent their aggregation from smaller peptides/oligos, or to…
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….
One of the other suggestions from Angela Glading at lab meeting a while ago was to quantify the vacuoles on different culture areas. So, I selected images from 3 different experiments (all at day14 of growth) and counted the number of cells which expressed vacuoles on different areas. I then used my mask code in…