THP Entry: Polymerase Chain Reaction, Cheaper Than A Hamburger

PCR Invented 30 years ago, polymerase chain reaction , or PCR, is one of the greatest inventions of the 20th century. It’s the technique that allows researchers to map genomes, find genetic causes of diseases, create Jurassic Park, and match crime scene DNA to suspects. When PCR was first invented it was extraordinarily expensive, and even today commercial PCR machines cost about the same as a new car. There is an open source project for a PCR machine that costs about $600, but for his Hackaday Prize entry, [David] is knocking a few more zeros off that cost and building a machine for less than the cost of a fast food meal.

Despite being the work behind a Nobel Prize, PCR is conceptually fairly simple: A strand of DNA is unwound into two strands, an enzyme, or primer, is annealed onto these single strands, and then biochemistry happens, turning those single helix strands of DNA into a complete double helix, ready for the next replication cycle. The key of the PCR technique is getting the enzymes and primers to react. This is only done at a fairly fine range of temperatures, cycling between 90°C, then 60°, then 72°C.

The oldest models of PCR machines used multiple water baths, with newer commercial machines using something that probably justifies their cost. The OpenPCR project uses an aluminum heater block, but [David] is going for a modern twist on the old-school method. He’s trying to figure out how to exploit convection to get local temperature variations in a single vessel. How he’s going to do this is anyone’s guess, but building a PCR machine for $5 is pretty cool.

SpaceWrencherThe project featured in this post is an entry in The Hackaday Prize. Build something awesome and win a trip to space or hundreds of other prizes.


  1. zuul says:


    yes you can just stick your DNA and master mix in a tube and put it in hot water and manually increase the temperature then turn it down and do it again and again like 32 times to do PCR..lager margins of error, tedious and you could possibly lose your whole sample if the tube opens

    he’s probably going to put a servo on the heat control and make it cycle that way..but the entirety of it isn’t going to be less than $5,..he did say he had to up the price so MAYBE $10 or so,… but then you still need reagents if you’re going to do PCR so it’s still
    a little pricy

    the problem with THP posts is that people can make outrageous claims and not have to show anything

  2. Joejoedancer says:

    Hackaday is being troll’d. Here is a thermal cycler for 160$.
    you can also use water baths to do the same thing.

  3. dsioioo says:

    i think we have winner

  4. Shakipu says:

    As Kary Mullis (inventor of PCR and Nobel Prize), this guy ([David]) might have taken some LSD to get his ideas.

    • @Shakipu – I suspect that [David] may be one of the “sour grapes” that are pissed-off at Dr. Mullis for taking his leave from CETUS unexpectedly. I can not understand the interest [David] has in PCR and why he thought we HaD’s would join him in that.

      Of course Dr. Mullis is an odd-ball just like Nikola Tesla was in where you have to question his natural-idea-evolution, or as the anthropologist Paul Rabinow calls the “production of knowledge” or PoK – Paul does question Mullis too in his book “Making PCR”. Tesla claims his PoK came from dreams, portents, and trances. Dr. Mullis claims it was the LSD (lysergic acid diethylamide) and little green glowing raccoon ET at his California cabin (true story by him!).

      So any way DAVID… I’ll be your little green raccoon here… try using an Arduino to regulate your PID from 95° C to whatever temperature you want. As you know TEC’s work quickly and can be electrically controlled with negative to positive voltages. The Arduino can control timing too. It will bring the price up a few dollars but you will get the blessing of the HaD Arduino gods for it. (LOL)

      PCR may have an unexpected future in gene splicing and cloning arena. Who knows we may get to get a piece of Dr. Mary Schweitzer’s very labile skin sample from a arguably 65my extinct animal. Me personally I would love to see a $10 DNA sequencing kit to make forensics a DIY project rather than this (I love San Diego damn it! – LOL):

      • David says:

        Yes it IS arduino based! But no, no TEC’s, as that would blow the budget. Instead, I’m using fixed-temperatures that are generated with cheap ceramic heating elements (Arduino PID controlled of course :)


  5. threepointone says:

    I can’t believe they’re doing it at $600…that’s not too far from some of the low end commercial models, which are probably a bit more trustworthy if you’re trying to get accurate results. I’m also having trouble finding the target audience for this product (it doesn’t seem lab grade at all, too expensive, pipettes you need to accurately prepare the reaction and other equipment will add up to more than the PCR machine, probably not particularly easy to store, handle, and obtain reagents if you’re not an actual lab) Having done some thermal design on these systems, I’d agree with the first poster. Before people had fancy PCR machines, it turns out people like Kary Mullis just did PCR with oil baths at different temperatures…and for the sacrifice in labor, you actually get much higher performance. The ramp rates of most PCR systems is largely limited by the thermal mass of all the unnecessary components (metal block, heater/cooler). If you have multiple uniform (thanks to convection at elevated temperatures) heat baths, you don’t need to quickly heat or cool anything but the plastic tubes (which are admittedly thermally slow) and the solution itself. Usually PCR performance, speed, and accuracy can increase with better thermal speed.

    • I think the introduction of thermostable “Taq polymerase” (from a bacterium that lives in hot springs and hydrothermal vents in our US national parks) changed the PCR process drastically. Now the sample doesn’t get destroyed so easily by high temps. I would think that would drive the expense down rather than up. You just need a supplier of Thermus aquaticus. Most likely from the “black market” as our National Park service closely monitors TAQ collecting now by universities and companies like CETUS. US-NPS wants a share of the money too I guess.

      J Robbins (11/28/2006). “The Search for Private Profit in the Nation’s Public Parks”.(

  6. snow says:

    oh GOD seriously? there’s so many mistake it huts my eyes. how can you confuse a thermocycler with PCR and a primer with an enzyme?? first of all a PCR reaction will always cost about as much as a hamburger because the enzyme,primers and nucleotides are expensive. you use two primers that will anneal on both strands of the DNA and the enzyme “will do the rest”. you use a thermocycler (yes that’s what he’s building) to do PCR but its not a synonym. PCR is the reaction and the thermocycler is the equipment to do it. that being said the project sounds interesting but i somehow doubt it will be as easy as he thinks.

  7. thanatox says:

    I do see a market for low cost thermocyclers in classrooms. As a teacher I would love to have one but the commercial models are way out of price range. However $5 or $10 is comically low. What it means is that you will spend way too much time troubleshooting. I’d MUCH rather see a $100-$200 version that works.

    Also, once upon a time doing a PCR involved switching a rack of tubes between 3 water baths every 30-90 seconds for 3 hours.less than $5, but now you have to decide how much your time is worth.

    • David says:

      Using the design I use works well AND is cheap. With a cas, safety switches and user interface with LCD etc, it would cost maybe $100-$200, but the most basic version will work well for under $10 (and maybe better that commercial machines for 1000x the price). The classroom and DIYers is the target!

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