Author: Karl Smith

We’ve been wondering for some time just how the thinness of our membrane will affect the concentration polarization behavior of solutes. Because solutes with sieving coefficients less than 1 are (by definition) moving slower than the solvent around them, in the area before the membrane their concentration increases. In the case of proteins, this so-called…

I’ve been on a Sepcon assembly binge, and I thought I would post my assembly statistics. On 12/15/13 (assembly “L”) I broke 28 chips out of wafer 1070. 3 chips were visually damaged by the break-out process, 1 was already defective. After inserting the chips into the sepcon housing, testing with 5 psi nitrogen revealed…

The Wiesner lab at Cornell (whom you may remember as the discoverer of the neutrally charged but highly fluorescent “C-dots” Jess used for her charged-based separation work) are about to publish Asymmetric Organic-Inorganic Hybrid Membrane Formation via Block Copolymer-Nanoparticle Co-Assembly in Nano letters. Building upon their previous work on block copolymer self-assembling films, they have added titanium dioxide nanoparticles…

EDIT – 2/10/14 – Adding 1 mM phosphate buffer fixes the problems outlined in this post. I’ve been having some trouble taking consistent pH measurements with the new pH probe. Prior to Thanksgiving I made a spectrum of 10 mM KCl buffers (at 4, 6, 7, 8, and 10 pH units) for use in my…

My streaming potential device is now working consistently. It turns out that the problem was the concentrations of salt that I was using. The Debye Length (the distance over which charge-charge interactions are important in an electrolyte) is given as , where   is the debye length in nm and  is the molar concentration of…

After last week’s post detailing the problems I’ve been having with my streaming potential setup, Jirachai was kind enough to come by the U of R last friday to look at my device. We banged our heads into the wall for a good two hours, but the drifting potentials and apparent insensitivity of the streaming…

A few weeks back I had finished my streaming potential/electro-osmotic pump setup. It looks like this: For streaming potential measurements, we pressurize a tube filled with 100mM KCl that connects to the membrane and measure the voltage drop across the membrane. When I first applied a pressure to the setup, the voltage drop did seem…

Back when I first joined the lab I did some experiments where I varied the pressure driving a gold filtration experiment. The critical plot was this:   It seems unlikely that the sieving coefficient could change so dramatically with applied pressure, so I would like to repeat the experiments. Because the larger gold particles on…

I’ve been working on building a streaming potential/EO device for a while now. This was Yaron’s prototype: Which itself was based on Jess’s design: I didn’t like that the device needed to twist together, and also that it was designed for the old circular 2-slot sepcons. My first prototype used the machine vise downstairs for structural…