I performed separations using C-dots from Hybrid Silica, a silica based particle with an internal fluorescent core.  The particles are coated with a PEG layer of unknown length, but the idea would be that they’d be less affected by electrostatics than gold.  I used two sizes.  One is marked <10 the other <30, but I…

There has been some experimentation recently on trying to form very large pores in thick membranes.  We have found that a high temperature anneal (1000 C) along with a fast ramp rate (100 C/s) w/o the susceptor can create these large voids. It seems that the distribution widens as we push the cut-off up.  The…

For the last three weeks, we have increased the substrate bias power from 25 W to 32 W (for both oxide and a-Si) to adress some film quality issues.  I have found that it is “harder” to open pores in a film deposited at higher bias.  Below are micrographs showing the difference in porosity for…

I have been working on using the membranes to trap blood cells so that I can take force measurements with the AFM.  It is impossible to perform AFM on blood cells resting on a coverslip because the water displaced by the tip on the approach pushes them away, so I am trying to use a…

Dave gave me some carbonized samples several weeks ago to test stability/discoloration.  I measured the contact angles right after I got the samples (posted here) and then started the discoloration.  These are SC141 chips.  Controls were untreated (1st column) and RTP’ed only (2nd column) chips.  Two carbonization conditions were tested – 5 minutes of 1…

I have observed that in some cases the rate of EO can go up or down over the course of an experiment.  Often the initial burst in the first 5 minutes is high, then the rate may stabilize or drop.  I have observed that the rate of EO seems closely related to the current.  Here…

I got some new data on the pnc-Si capacitive sensor that has not been published on the blog yet. All of the results are summarized in the Spring MRS Proceedings paper mrsspring09_kavalenka. I also uploaded presentation that I made on MRS in “Presentations ” section of the blog. I will talk more about this data…

This is a short review of a few experiments that Tom had set up this morning. Carbonized membranes: A few carbonized membranes that were used for permeability measurements were tested in EO.  The membranes were left in the sepcon, which was filled and placed in a reservoir.  Electrodes went inside the sepcon and the reservoir. …

Previously, I had data showing that 5nm gold in 10mM salts went diffused through pnc-Si membranes.  I was able to achieve this twice, although the second time took two days before the gold signal was intense enough to observe via absorption. Here’s what has happened recently: 5nm gold will not pass through untreated SC 168,…

Here are the results of diffusion based protein separations at different salt concentrations and 50kD Microcons: We see a sharp cutoff between 31 and 45kD.  Separations look like they have progressed further in 10mM salts rather than 100 mM (this is the opposite of what we see in pnc-Si).  The 100kD data may also support…