The following is a plot of rhodamine diffusion for the experimental system at various time point: In this figure, the rhodamine approaches equilibrium, as defined as a filtrate/retentate value of 1.  The 9x well chips have a larger active area…

Due to the discrepancies between the 1D model and experimental runs with rhodamine, I have switched over to using COMSOL to solve for a 3D model.  In this system, 200×200 um membrane squares with a 45 degree etch separate the two…

In order to further test the model, I’ve set up additional rhodamine diffusion assays.  In each case, the setup is similar to the nanoparticle/protein/dna separations –  20 uL of .5 mM rhodamine on the top of a SepCon and 20…

Frustration with the lack of agreement with experimental device has led me to check if the diffusion in the wells within the model is physically relavent.  To do so I’ve solved a partial differential equation pertaining to a concentration of…

In effort to understand the model, I have been studying simple diffusion experiments using rhodamine, a small molecule expected to experience little hindrance.  The model currently expects a small molecule the size of rhodamine to reach equilibrium within 1.5 hours.…

This is an update of my progress with the diffusion model.   Sieving coefficients for standard setup (Renkin only) In this image there’s a strong sigmoidal curve for the 24 hour diffusion.  However, the cutoff (~34nm) is higher than cutoffs…

In an effort to measure the effects of bsa adsorption on pnc-Si, I made some samples from SC 073 (a good wafer for separations) and with the help of Graham Marsh (Waugh Lab), looked at them using AFM.  We did…

Here is the analysis of the wafers used in the pressurized gold separations: SC 199   Stat Result Mean Equiv Diameter 17.84 nm Median Diameter 18.30 nm Porosity 2.2% Weighted Mean Diameter 20.81 nm 90% Diameter 26.64 nm Roundness .782…

This previous post contrasted how gold could be separated by pressure in deionized water, but not by diffusion (w199).  I checked up on that diffusion sample again after 6 days, and while the retentate had mostly evaporated, there was no…

A paper by Munch (from Kodak), Zestar, and Anderson in J Mem Sci (1979) writes that charge has a big effect on albumin separations in track etched membranes.  They show in their paper that they can make the theoretical sieving…