Nature Commun.http://doi.org/hxh (2012)

Most organic electronic circuits designed to interface with biological systems have to balance electrical connectivity with stability because the ion-rich electrolyte that such systems contain generally degrades device performance. Ionic bipolar transistors, which are based on ion-conducting polymers, could in principle circumvent these challenges. Because conduction in these devices is intrinsically ionic, they can be operated in electrolytes, and can even modify the composition of their environment, albeit rather slowly. Ionic bipolar transistors are based on two cation- or anion-selective electrodes, a channel from a neutral polymer electrolyte, and a base electrode with complementary ion selectivity that controls the salt concentration in the channel and thus the conductivity. Magnus Berggren and colleagues have now integrated such devices in unipolar and complementary inverters and NAND gates. The circuits have a signal range of 10 V and low energy consumption. Such gates form the basis for more complex logic circuits and could be used to gate and distribute chemical signals in biological and medical applications, the researchers suggest.