I tested four membranes with different porosities today, including one that had been carbonized. Here are the pore size distributions with TEM micrographs. I ozone treated all the samples prior to running the experiments, including the carbonized sc 582. I expected some of the carbon ring to oxidize, which TEM confirms: It would appear that…
Last week, I finished up an initial experiment to investigate whether pnc-Si membrane geometry affects cell morphology. To do this, I used a mask with 2×2 arrays of different size squares and also samples with 4 slits of different lengths and widths. A lot of the samples broke before I got the wafer, so this…
I did two tests using water straight out of the Barnstead and with water from the cleanroom in Hopeman. I was able to maintain high permeability using the same membrane for at least three successive trials with both. It looks like the culprit is the Nalgene container used to store the water. For any sensitive…
Hi all! Above is an image of the bioreactor made from the square, 5-slit pnc-Si chip and a PDMS structure. Fused-silica capillary tubings were inserted into the bioreactor to form the inlet and the outlet for the transfer of the cells into the lower compartment, which is made entirely out of PDMS. Note that the…
I’ve become increasing suspicious of the membrane clogging during the hydraulic permeability experiments. I ran an experiment where I took three fresh samples (sc 582) and pushed water through for 5, 10, and 20 minutes. Ideally, the permeability would be the same for all three time points. However, I observed a decrease at each increasing…
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…