In the past, we have seen allyl alcohol treatment on silicon chips helps retain a low contact angle longer than a purely plasma treated sample does. This helps us maintain gold flow in a sepcon format for a longer period of time compared to untreated or a purely plasma treated sample. Untreated samples also will…

In this post I look at our membrane resistance and compare it to the best performing alumina membrane. Here is the resistance figure I made for the paper: This figure shows the device resistance with and without a membrane.  The membrane resistance would be the difference between the white and grey bars.  We would like…

We ordered quantum dots from Invitrogen.  These QDs have a PEG coating that terminates in COOH and should cause the dots to be negatively charged.  They are about 12.6 nm in diameter: They exhibit a -40mV zeta potential by zetasizer measurements, however the particles appear to aggregate a great deal (under microscope and visibly turn…

Small DNA oligomers behave like stiff cylindrical rods.  They have both rotational and translational diffusion, and this is of interest when considering how such a rod will diffuse through a nanopore.  In this post I briefly consider the effects of rotational and translational diffusion of cylinders of different lengths. The rotational diffusion coefficient can be…

The paper that came out from Shigeru’s laboratory earlier this year in Analyitical Chemistry (Ishimatsu et al. 2010 downloadable here) demonstrated that the permeability of pnc-Si membranes to small monovalent ions in 0.1 M salt is predictable from membrane geometry alone. The paper also shows that multivalent and/or large ions do not follow theory as…

PhD Dec. 15, 2010 Thanks for Everything!

In continuation of work on ultrathin metal electrodes on pnc-Si, I tried changing metal thicknesses at different positions inside the chamber.  In this experiment, on the front side of the 30 nm thick membrane the 22 nm metal layer was deposited from three different positions in the same run. The back sides of all the…

This is an update of the research on the on-chip EO pump. Due to a mistake in determining the direction of particle flow, it now looks like the particles in this post were moving by electrophoresis rather than electroosmosis.  The particles were negatively charged (-40 mV zeta potential) because of a COOH group on the…

Using fresh tips, I re-ran the scans of amorphous Si films deposited at different biases. Recall that our theory states that interface roughness between the Si/SiO2 is an important determinant for ultimate pore morphology. A rough interface will suppress nucleation, which is why we observe low porosity with zero bias. The 05 W condition decreases…

In my last post, I introduced the concept of pore size dependent carbon growth on alumina coated membranes. Here, I have plotted a Gaussian fit of the tail of the pore size distribution of carbonized membranes (with and without an alumina coating). I am only showing the tail of the distribution to highlight the sharpness…