Status report, part II: It's gonna be a bright orange Christmas...

19 Apr 2011

As promised, here's the second half of the BioBoard GGHC 2011 project:

At yesterday's meeting, our two chemists really got their act together to show off some truly awesome skills - Sean's long-awaited ruthenium catalyst for the dissolved oxygen sensor had finally arrived, and Otute brought in what initially appeared to be some rather odd Christmas decorations, but turned out to be one of the coolest hacks I've ever seen: home-made pH sensors from glass baubles! It turns out that the glass in those things is thin enough to be permeable to hydrogen ions (H+), which is what we want to measure when we're talking pH, so all you have to do is strip off the metal coating, remove the little hanger, and you have the makings of a rather large, but perfectly functional glass pH electrode. Take a look at this:

Isn't that just the coolest thing ever?! Only one problem - they're huge (approx. 2 inch diameter), and in order to work, they need to be filled with potassium chloride (KCl), and attached to a reference electrode in a separate, also KCl-filled chamber, so any pH probe built using these is going to be seriously bulky. Obviously, Otute had already figured that one out, so he's gone ahead and built a second variety based on the paper we referenced in last week's update - this one made from disposable pipettes using a PVC matrix membrane instead of permeable glass. We managed to at least get a response when we measured them with a voltmeter (although it's rather far off the mark), so with a little more research on the current flow between the electrodes, and a little more tinkering with the pH amplifier circuit that Rolf is trying to create using the pHduino as a model, we might actually end up with a real pH probe. I managed to get a quick shot of Otute himself holding up one of the pipette prototypes filled with KCl and silver wire in place:

Meanwhile, Sean has been waiting for three weeks for the elusive ruthenium complex catalyst for his dO sensor to arrive - and at long last, it has! So he was very excited last night, and understandably so - finally, we got to test whether the basic theory actually held. The idea is that the ruthenium complex is excited by blue light (approx. 470nm), and glows a bright orange in the presence of oxygen, the concentration of which can then be extrapolated from either the intensity or the lifetime of the flourenscence. In order to do this with any accuracy, we need to be able to correct for background light, so the ruthenium complex is layered between mylar (oxygen permeable) and vinyl (impermeable) and irradiated two different LEDs, one blue and one red, and the flourenscence is then meaured with a broad-spectrum photoresistor. It sounds complicated - and it is - but not quite as bad as one might fear...no lab required, so you can do this on your kitchen counter, as long as you clean it thoroughly afterwards. None of the ingredients are toxic, but your food might taste funny. Anyhow, we managed to capture some shots of Sean playing around with the chemicals, and a beatiful shot of the Ru glowing brightly orange under blue light:

That's all for this time, folks. Hope you'll stay tunes as we forge ahead on this last mad rush to get all the sensors built, tested, wired up, talking to the Arduino and transmitting all their lovely lovely data to our database. Whether or not you do, just don't forget: Be excellent to each other, dudes!