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.

Genetic Research on the Cheap

When you think of DIY hardware, genetic research tools are not something that typically comes to mind. But [Stacey] and [Matt]‘s OpenPCR project aims to enable anyone to do polymerase chain reaction (PCR) research on the cheap.

PCR is a process that multiplies a specific piece of DNA a few million times. It can be used for many purposes, including DNA cloning and DNA fingerprinting for forensics. PCR is also used for paternity testing.

The process involves baking the DNA at specific temperatures for the right amount of time. The DNA is first denatured, to split the helix into individual strands. Next, the temperature is lowered and primers are bound to the strands. Finally, another temperature is used to allow the polymerase to duplicate the DNA. This process is repeated to multiply the DNA.

The OpenPCR uses an Arduino to control a solid state relay. This relay provides power to two large resistors that act as heaters. A MAX31855 is used to read a thermocouple over SPI and provide feedback for the system. A computer fan is used to cool the device down.

A milled aluminium sample holder houses and heats the samples during cycling. The laser cut, t-slot construction case features some helix art, and houses all of the components. It will be interesting to see what applications this $85 PCR device can perform.

Via Adafruit