The saga of the space plates

Here is a conundrum. Suppose you want to measure growth rates of bacterial cultures in an aerobic environment, on LB, in 96-well plate format. So, you buy some plates from your favorite supplier, and program them dispense some LB into the wells with a multichannel pipetter, inoculate from whatever your source is, and pop it into your plate reader and start the program.

Now, what do you do if your plate reader was installed upside down? Your media will spill out and get all over the expensive bits inside the machine, and your PI will become sad and despondent. You could perhaps put the plate in upside down too, and that might solve the problem. What if the instrument randomly changes its orientation as the experiment proceeds? Or worse yet, what if the instrument is permanently in free fall? What then, kemosabe?

One would think, I suppose, that NASA has a thing for that. And you would be correct, to a point. The problem is that the thing in question is not ready yet, and the experiment is going ahead without the thing. So, here is your mission, should you choose to accept it : Design a cup that doesn’t spill when it is open.

I must admit I toyed with the idea of 3D printing an array of Klein bottles, but settled on fabricating plates out of acrylic and PDMS. I’m relying on the strong hydrophobicity of PDMS to prevent liquid from entering the ventilation ports.

The International Space Station needs to maintain very strict controls on volatile compounds off gassed from they bring aboard, which means rules out a lot of useful things, like pretty much every glue you can think of. So, another advantage of PDMS is that it is food safe. In fact, it is an ingredient in many cosmetics and foods, including McDonald’s Chicken McNuggets. Now, the idea of eating silicone elastomer, the same material used in the front shock absorber on my mountain bike, may not sound appetizing, but it there is pretty good evidence that it is at least not demonstrably harmful. So, that should hopefully keep us well clear of toxicological issues.

I’ll wrap up with a poem from my childhood.

Three jolly sailors from Blaydon-on-Tyne
They went to sea in a bottle by Klein.
Since the sea was entirely inside the hull
The scenery seen was exceedingly dull.
The Space Child’s Mother Goose, Frederick Winsor & Marian Parry

Posted by Russell Neches

on 29/04/2013 at 04:30 under a Creative Commons Attributuion License.

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