Here is a look at all our water permeability through nanomembranes to-date. There appears to be subtle trends showing increasing permeability with radial position (r – values) and a not-so-subtle trend showing decreasing flow with protein (cyt and albumin). Note that with the more recent membranes we’ve been able to do repeats. The permeabilities are…
Wafer 302 appears to have no pinholes and held up pretty well in the centrifuge, up to 5psi for many hours in a wet-wet format. Here are some quick numbers on flow rate over 2 hours, 3.3psi, including radial position:1x PBS (no protein)68 uL (r=4.1)91 uL (r=4.1)99 uL (r=4.5) Using Jim’s new equation. 99uL of…
I derived the governing equation for the volume transfer from SepCon devices in the wet/wet (EQ) format. It is … where the equilibrium volume for the cup can be calculated apriori using the cross sectional areas of the cup and the surrounding annulus … with the total volume of interest given by and the time…
This is probably not of general interest, but for the sake of full disclosure, I have spent considerable time working with our wafer supplier (Virginia Seiconductor) to resolve some issues regarding the surface quality of their wafers. It would have been much more productive to simply switch suppliers, but unfortunately, they are the only place…
After the w310 series being beautiful (few pinholes, reasonable strength, high yield), we have retreated somewhat with a return of the copper-related piholes. Here is an SEM image and EDX scan from the well wall: Here is a pic of a pinhole on the membrane with a telltale copper silicide particle attached to the edge:…
SepCon EQ reaches Equilibrium in 2 1/2 hours!w310 (no pinholes)1x PBS (no protein)2 hours @ 1000rpm (3.3psi) -> 103 uL passage (56 uL/(min-cm2-psi) )2 1/2 hours @ 1500 rpm (5 psi) -> 204 uL passage (>74 uL/(min-cm2-psi) ) In the second case, the sample visibly reached what looked like equilibrium. It was not quite exact,…
last week I ran some tests using a single 100K microcon filter; this week I preformed essentially the same tests but instead of testing one filter over the entire pressure range I used a new filter at each pressure. I tested the permeability at 1.35psi, 21.63psi, 118.7psi, and 267.1psi; each pressure was tested using three…
Permeability data first:Wafer 310r = 4.3 units from centern = 32.0 mg/mL cytochrome C in 1x PBSmean permeability = 27-33 uL/(min-cm2-psi) *** corrected to account for (2) 115x2014um slits[The range is due to variations in measurement and total accounting for initial uL]Wrapping with parafilm resulted in only a mean of 13uL of 1000 initial uL…
Jim’s post inspired me to think about wetting of nanochannels. We raised this question before – Do we wet the channel in our membrane when water is applied to only one side? My guess was yes because of our success in diffusion and convection when we expose both sides of the membrane to water. The…
The following contribution comes from Jan Hoh – a Professor of Physiology at Hopkins, an invited speaker to BME in December, and a potential future collaborator. Jan sent his thoughts on why it is impossible to get flow through our membranes in a wet-dry format. The bottom line is that surface tension theory says that…