DNA computing is a branch of computing which uses DNA, biochemistry, and molecular biology hardware, instead of the traditional silicon-based computer technologies. A brief introduction of the field can be found on the site of the Qian Lab:
How can we rationally design and synthesize molecular systems with programmable behaviors? Life is full of amazingly sophisticated programs encoded in genomes, orchestrating molecules to sense, to compute, to respond, and to grow. One approach to interpreting the molecular programs that nature creates is to explore and re-realize the principles of information processing in biology, for example by rationally designing and synthesizing molecular systems that exhibit programmable behaviors. As much as electronics has changed our lives, at a much smaller scale computer science in its new form as molecular programming will change our lives with nanomachines, smart drugs and diagnostic devices.