From 2007.igem.org

Bio-diode: The diode, one of the most significant parts in the electric integrate circuit and electronic equipment, functions as allowing the current get through when the diode is positive-biased, and cut off while it is negative-biased. When the negative voltage increases to a threshold, the diode tends to be negatively broken down. In this project, the molecular signal AHL is considered as the current of electric circuit, the generator, amplifiers, blocks and detector cells are constructed with the parts provided by MIT and then are equipped in series in order to achieve the cellular and molecular biological diode.