I used the transwell track etched membranes for these permeability experiments.  I first looked at 5nm gold in 10mM KCl.  After 24 hours the retentate and filtrate had just about equilibrated: We can compare these scans to the stock 5nm stock solution and see that the height of the 525nm peak is related to the…

Last week, we ran a series of wafers with three different Si thicknesses (15 nm, 30 nm, 50 nm).  We wanted to explore how morphology shifted with film thickness.  Below are three membranes that were annealed at 800 C with no susceptor and a ramp rate of 100 C/s. As expected, as film thickness increases…

So I think I have confirmed that PDMS is at least one of if not the major contributor to the contact angle problems in the UV-ozone system. Control image before any treatment: I then dried the chip and placed it in the UV-ozone system with two slides that each had two strips of PDMS. Since…

Nakul and I noted last week that the UV-ozone system was not performing. We took pictures of control and treated samples (2x) to measure contact angles on Amorphous, pnc-Si, Oxide and Nitride TEM grids. Our results were pathetic – most samples had less than a 10 degree decrease in contact angle, staying near 60 degrees….

I wanted to have 3 repeats of the previous salt-tuned separations.  I’ve gone through and performed the densitometry on a couple more gels and compiled the results. 100mM: The first two experiments were from the two experiments set up on the same day.  The third (yellow triangle) was set up a different day and does…

One of Christine’s projects was to determine if pinholes affected electrical resistance (TEER) measurements.  She summarized her work here.  I collected her data and did some negative controls to finish this work up.  Here’s the graph: The “no membranes” data is from Sepcon transwells with pnc-Si chips but without membranes (I broke them before assembling…

Separations were performed at 2 different salt concentrations with equal volume filtrate and retentate (to avoid dilution problem). Separation time was 40hrs rather than the usual 24. The lower salt concentration run has a lower cutoff – which is just like what we see in the DNA separations. Remember though that proteins have different charges…

Christine and I have been looking into whether the O-ring position affects transport through pnc-Si transwells.  The hypothesis was that the unstirred water layer under the Sepcon might be diminished by switching the O-ring from its normal position (“O-ring bottom”) at the bottom of the Sepcon to above pnc-Si (“O-ring top” or “pnc-Si bottom”).  This…

UPDATED: More sizing characterization (see chart and figure below). We recently purchased our own gold ladder, and today I’ve done some of the initial characterization.  Particles come in 5, 10, 15, 20, 30, and 40nm.  Here are the absorbance scans in both water and 10mM KCl: The scans look similar, so none of these particles…

Anant and I have been doing long-term discoloration experiments for the past few weeks.  We set up samples in “ideal” conditions – pnc-Si in transwells with pnc-Si side down, autoclaved samples and in the incubator (lower OH-).  The only non-ideal component is the use of DMEM+10%FBS with high NaHCO3 (3.7 mg/mL).  Chips were RTP’ed at…