So one thing that has been a back burner project which might suddenly become a high priority one due to work with a professor, would be DIY
microfluidic devices.
Now I'm wondering, what kind of devices would sciencemadness.org members find useful.
As a general rule - no organic solvents, the materials involve won't handle them typically (as a large proportion of the reaction mixture, an aqueous
solution with organic components is quite fine).
Keep in mind, at such low volumes, they are mostly diagnostic/qualitative. Separations occur very quickly in microfluidic devices, so a small
chromatography device comes to mind. Also reactions proceed relatively quickly, and in some cases very high yield, due to the fine mixing and lack of
diffusion rate limiting in such a small volume (which can reduce yield to some degree).
So probably the devices would fall into 2 categories:
1. Reaction vessels (mix reactants together, can possibly be heated)
2. Separation devices (chromatography, electrophoresis)watson.fawkes - 18-1-2010 at 06:54
The chlorate-and-perchlorate crowd here has use for this kind of technology. pH detection is difficult in a chlorate cell because electrochemical pH
probes are attacked by the liquor. A microfluidic titration rig would do nicely. A second application is nitrite detection in a lead dioxide plating
bath of lead nitrate.aonomus - 18-1-2010 at 07:25
Hm, that might be a bit trickier, plain microfluidic devices are easy enough to make by etching out a brass metal master, then using PDMS silicone
resin to cast the form. Microelectrodes are harder to make apparently from what literature I have done.
I'm not very familiar with chlorate/perchlorate processes, what would the actual chemistry behind finding the pH be? Electrochemical or titration with
an indicator?12AX7 - 18-1-2010 at 08:31
Electrochemical pH = measure the voltage of any reaction that depends only on [H+]. You're measuring the Nernst potential, -59.2mV/decade, not so
much any cell reaction.
I understand most probes are sintered glass, which is a fine barrier but will allow diffusion, and I suppose if they're using an Ag/AgCl/saturated KCl
electrode, it might be affected by the chlorine in solution. An H+ porous membrane would be better, as long as it isn't chewed up by the corrosive
solution (PTFE, PVDF, ???).
Microelectrodes are harder to make apparently from what literature I have done.
I'm suggesting not using an
electrode at all, but rather a titration with a visible pH indicator. You'd use separate electronics to sense color change, so there would be no need
to integrate wiring into the fluidic processor as such.
