Looking back at production over the last year, I noticed that our porosity has dropped considerably.  Now that we have a good handle on controlling pinhole density, it is time to focus on controlling morphology again.  Below are two examples of a 15 nm and 30 nm pnc-Si film produced this month and one year…

In a first attempt to reduce the electrostatic drag that might be slowing water transport, I ran an experiment with 1x PBS.  The membranes were first ozone treated and then assembled into the SepCon inserts. From these first trials, it appears that PBS does pass through more quickly than DI water.

In this post I will describe recent streaming potential measurements for PES membranes and the calculated apparent zeta potentials from these measurements. Setup: 1. Fabricate Ag/AgCl electrodes: Silver wire at the anode in 1M KCl at 1mA current for 20 minutes. 2. Assemble streaming potential device: Electrodes are inserted into silicone chord o-rings and chamber…

In an attempt to help wet the pores prior to permeability experiments, I’ve started soaking assembled SepCons in a %50 ethanol solution.  Each SepCon is inserted into an eppendorf so that the membrane side is fully submerged.  I realized that in my last post, I was soaking multiple samples in a beaker which did not…

In the next paper that I’d like to publish, I will compare protein separations for two membranes with different pore distributions to a single membrane at two salt concentrations (basically a redo of this post).  My most recent trial with this had less than stellar results. I chose two wafers for movable cutoffs – SC…

I’ve recently been exploring hydraulic permeability using the pressure cell.  As you may recall, the majority of our permeability measurements have been done in the centrifuge (EQ format or closed bucket).  The pressure cell allows for a more accurate measurement of permeability because it is not affected by changing water levels or variable driving pressures….

I’ve updated by 3D separations figure by using actual DLS sizes rather than the dimensions roughly obtained from crystal structures.  I have run into a snag with reporting the data however – use sizes by intensity or sizes by number.  The difference is due to the fact that the raw DLS data is from intensity,…

In the previous post, I discussed how we could evaluate the flux of molecules through the membrane and alluded that this method could be used similarly to our effective diffusion coefficient manner of evaluating membrane impact.  Here are results of the full comparison. Standard setup: 15nm membrane, 1 hour time point, 1mm fluid wells, 5%…

In this post I take a look at the flux of molecules through the 1-D membrane simulations.  I will then use this flux to compare to systems lacking a membrane. First off, how to find the flux.  Inside the membrane, the Flux = -Dm dc/dx.  Unfortunately this is extremely hard to calculate because of the…

To identify how much of an effect the membrane has on particular simulations, we originally came up with the idea of using a phenomenological effective diffusion to view the membrane impact (see this post).  Here is the most up to date version of the figure, which was slotted for use in the simulated diffusion paper:…