FORGET smartphones, how about a smart arm? Human cells capable of performing simple arithmetic could one day be implanted in your body as a biological computer to diagnose disease, administer drugs or interface with electronic devices.Martin Fussenegger and colleagues at the Swiss Federal Institute of Technology in Zurich created biological versions of two key digital circuits inside two sets of embryonic kidney cells: a half adder and half subtractor. As the names suggest, they add or subtract two binary numbers. These are the most complex biological circuits ever created, and could form the building blocks of more advanced computational circuits.
