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…

Previously I had posted a chart depicting the permeabilities of SepCon membranes from w310. I went back and noticed some errors in the equations. Here is an updated version of that chart. Also included is a sample where I used the ultracentrifuge to clarify the protein right before the experiment, which should remove any larger…

Last week I performed spins with SepCons from w310. I tracked permeability and tried to perform some separations with proteins. w310 had high air permeability (link), but from my diffusion data it looked looked like the cutoff was possibly between beta-galactosidase and phosphorylase b (link). Myosin definitely did not make it through these membranes, but…

I ran the same 100K microcon system through numerous pressure ranges and put together the spread of hydraulic permeability results.These results show that the hydraulic permeability of the microcon membranes decrease with increasing pressure. Once I finished running the tests at these pressures I reran a test at 19.52psi (3800RPM) to see if we would…

I think the consistently low flow rates are a real bottleneck for all our fluid based experiments and must be overcome. On the production side, we are really pushing the limits of our capabilities to produce the current membrane geometry, which I consider to be crazy big at 0.1 x 2 mm!! Considering the 15…