I have observed that in some cases the rate of EO can go up or down over the course of an experiment. Often the initial burst in the first 5 minutes is high, then the rate may stabilize or drop. I have observed that the rate of EO seems closely related to the current. Here…
I got some new data on the pnc-Si capacitive sensor that has not been published on the blog yet. All of the results are summarized in the Spring MRS Proceedings paper mrsspring09_kavalenka. I also uploaded presentation that I made on MRS in “Presentations ” section of the blog. I will talk more about this data…
This is a short review of a few experiments that Tom had set up this morning. Carbonized membranes: A few carbonized membranes that were used for permeability measurements were tested in EO. The membranes were left in the sepcon, which was filled and placed in a reservoir. Electrodes went inside the sepcon and the reservoir. …
Previously, I had data showing that 5nm gold in 10mM salts went diffused through pnc-Si membranes. I was able to achieve this twice, although the second time took two days before the gold signal was intense enough to observe via absorption. Here’s what has happened recently: 5nm gold will not pass through untreated SC 168,…
Here are the results of diffusion based protein separations at different salt concentrations and 50kD Microcons: We see a sharp cutoff between 31 and 45kD. Separations look like they have progressed further in 10mM salts rather than 100 mM (this is the opposite of what we see in pnc-Si). The 100kD data may also support…
Since the last post we have been working on obtaining replicates with wafer 101 chips. The goal was to show salt dependent filtration changes. These chips were different from the ones originally used in that the pores were much smaller (7-15nm diameter) and did not exhibit any merging. It was suggested that we perform an…
The retrial on cellulose (100kD) gold separations gave similar results to the first study (results from Tecan scans): particle salt results 5 0mM no au in filtrate, retentate concentration 15 0mM no au in filtrate 5 10mM no au in filtrate, retentate concentration 15 10mM no au in filtrate I took the membranes and rinsed…
Inspired by JP’s work with the Veeco Wyko, I attempted to fit pressure-displacement curves with the equation for thin film deformation (Vlassak and Nix 1992) for two membrane geometries: 100um x 100um and 1000um x 1000um. The relationship between displacement and pressure is: P = pressure, d = displacement, C1 and C2 are geometric coefficients,…
This is just a little update on the results of the pnc-Si, cellulose, and pes separations. When I added up the retentate and filtrate, it didn’t always equal the intensity of the starting sample (keeping in mind that I was unable to collect filtrate from PES and should re-try that separation). I took the percent…
Can viscosity be determined by dynamic light scattering? Dynamic light scattering in essence measures the diffusion of particles and calculates the hydrodynamic radius using the Stokes-Einstein relation, D = kT/(6πηr). To find a size using dynamic light scattering, you need to input the viscosity so it can perform the calculation. If we don’t give the…