After all the nafion-coated pnc-Si chips that Jirachai gave me broke during my last attempt to filter salt water, Jirachai was kind enough to supply me with a new batch of chips, this one a mix of SiN and pnc-Si,…
Author: Karl Smith
Karl is the 'separations czar' for NRG. As a Biophysics Ph.D. Candidate, Karl has the responsibility of characterizing new membranes, modeling the unique physics of nanomembrane separations, and finding ways to apply pnc-Si technology to protein purification, nanofluidic transistors, and human hemodialysis. Karl graduated from Allegheny College in 2011 with a double major in English and Physics.
Effect of Membrane Morphology on System Capacity During Normal Flow Microfiltration (review)
pdf of Zydney Paper This paper tackles the concept of membrane capacity – the amount of fluid a membrane can pass before it’s flux declines (due to pore blockage or the buildup of a cake) to some arbitrary fraction of…
Posted in NRG
Attempting to use Nafion-coated chips for salt water filtration
Jirachi has been working to make thin nafion films using our membranes as a support structure. Nafion is polymer that contains a sulfonate group, and as a result acts as a proton wire, allowing for cations (+) to be transported across a…
Posted in NRG
Figure drafts for upcoming separations/fouling paper
Figure 1. A) A TEM image of a SiN nanomembrane. Circles with a rim are pores that span the thickness of the membrane, while grey patches are pits in the surface. B) A pore size histogram generated using image processing…
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Fouling Mechanism in Josh’s 20 nm, 100 nm SepCon data
These fits are done using the math outlined in this previous post. We assume an average pore size of 50 nm and an approximate number of pores in the membrane of 1E9. 20 nm particles: 100 nm particles: …
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Derivation of an Analytic Solution to the Problem of Flux Decline and Fouling in a Centrifuge Tube
In my previous post, I derived a formula for the time-dependent flux decline in a centrifuge-driven membrane separation, assuming that the resistance of the membrane was held constant. The problem with that approach is that, as Josh discusses in this…
Posted in NRG
Modeling Resistance in Josh’s Separation Data
In Josh’s forthcoming paper about clogging in forward and reverse configurations using 20 nm and 100 nm sepcons, we thought there was reason to discuss how the data agrees with the already existing models of membrane fouling. In this post,…
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Conductivity and pH measurements of aggregated gold solutions
After the disaster with the fridge freezing our gold nanoparticles and causing them to irreversibly aggregate, I figured that it would be a shame to waste the ruined gold solutions and so I took some conductivity and pH measurements with…
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Adding a Compressible Cake Layer to the Theoretical Model
In a previous post (linked here), I discussed a naïve way to incorporate concentration polarization into our theoretical model of the sieving of charged nanoparticles. Essentially, I considered the particles to be uncharged point particles that were subject to a…
Posted in NRG
Negative Data for Nanofluidic Transistors, Dielectic ‘Flowers’, and an Interesting Gold Filtering Behavior
I’ve been trying for a year now to make a nanofluidic transistor – a nanomembrane with a thin layer of metal coated in dielectric that allows for the dynamic modulation of the sieving characteristics of the chip. Beginning with the…
Posted in NRG
