From 2007.igem.org

Figure 1: The positive-biased condition of biodiode. Cell number in all three picture refer to the cell density of generator cells (4L). The middle graph indicates the concentration of AHL rises quickly to a high level after the amplifier cells are activated by the enviromental AHL signal (input signal). The biodiode could reach to the condition of positive-biased under a high cell density of 4L or a slow flux rate.(right graph)

Figure 2: The negative-biased condition of biodiode.