A thermal cycler is an
electronic temperature control device used to automate the
polymerase chain reaction. The machine consists of a control system, a block which holds the reaction tubes, and a heating/cooling system. In some early models the temperature control was acheived using a
fan and an electric
heater. More recent cyclers use a
Peltier element (a compact
solid-state heat pump) which is much more
reliable and can actually
cool samples below the
ambient temperature.
Briefly, the polymerase chain reaction involves timed heating/cooling of the DNA and Taq DNA polymerase to achieve exponential amplification of a specific DNA sequence. The thermal cycler does this automatically. It's a far superior system to a graduate student with three water baths, a stopwatch, and three hours to kill.
The polymerase chain reaction was initially patented by Cetus Corporation, and thus anybody using it in research has to buy a licence. Fortunately, any laboratory buying a thermal cycler is also buying a licence, included in the (expensive) purchase price of the machine. Originally, cyclers were only available through Perkin-Elmer, but now many companies sell them.