Verified working Lightbulb PCR!

L to R: ladder, neg control, neg control, positive, positive, ladder (diff conc)

L to R: ladder, neg control, neg control, positive, positive, ladder (diff conc)

Lightbulb PCR has been kind of pipe dream of diybio.  Today, I finished off the build started at Bosslab, and confirmed the results via gel electrophoresis on a torn-down GELIS box.  What you see above in the right-most red lanes are the real deal- amplified DNA (ladders with blue dye on outside, red with no dna is negative control.  Technical details will follow soon but I really need to hit the hay.  In lieu of documentation, here is what is known about the concept of lightbulb pcr.

There has been, to my knowledge, only one confirmed working build, which was done by Brian Blais.  You can see the work here. The title of the work is “A Programmable $25 Thermal Cycler for PCR”, in case that link goes dead.  It was done back in the day when the hardware was an Intel 486 with 8 M of ram!  With a parallel port!

This style of PCR machine was resurrected circa 2011 when Russel Durrett did a build using PVC, a computer fan, and a lightbulb all controlled by an arduino.  Theoretically it was a good build, but I never saw actual results, which discouraged me from building it, due to the physical constraints of the system.  The issues stem from the use of air as a conductor of heat to the samples, a lack of heated lids and a lack of sub ambient cooling.

Using air as a conductor is really a killer, since heat distribution can be influenced by the lightbulb sitting at an angle, or air currents in the room.  Air is really not a good conductor, and this means that the feedback sensor is at a different temperature than the sample, which is no good.

At the same time, it is a brilliant build because literally all the parts can be found either at a hardware store, or at a hobby electronics type store.  And it works.  Maybe not reliably, but it works and it is cheap, so that is a good start on a tool, if someone is willing to invest the time.

Anyway, a post tomorrow will have a rough BOM, electrical schematics, and code.

Posted in: ENG

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