Re: [DIYbio] Electronic requirements for redesign of Arduino PCR thermal cycler

The reaction mixture will condense on the coldest part of the pcr tube, for instance, any surface not enclosed in the main heated block and exposed to ambient air.

One solution is to establish a temperature gradient from the top of the cap to the block by touching the cap with a second hot surface, preferably hotter than the main block such radiative and conductive heat transfer from the heated lid raises the temperature of all surfaces of the pcr tube exposed to air above the current temperature of the block. 

But you don't need s Peltier to do this. You just need a heat source you can keep at a constant temperature guaranteed to be hotter than any of the pcr temps.

It would be interesting to explore a hybrid design combining dynamic conductive heating in the tube block with constant radiative heating from a lamp or hot air flow positioned at just the right distance, instead of a heated lid in constant contact with the cap. Can the radiative heat source be set up to always add +20C to the exposed cap and 5-10 C to the reaction mixture? If so, perhaps such a design could lead to faster ramp times, by switching the radiator off during cooling.

Does the transparent plastic most pcr tubes are made from absorb IR?

Or maybe all that matters is if the reaction mixture absorbs the radiative energy. Not sure. Would pcr work in a transparent Quartz vessel in a freezer that was pulsed by a powerful IR source? Or would that be condensation city?

Cheers

Mac