Polyaniline grown into pores of polycarbonate membrane has been shown to behave like a microelectrochemical transistor. The nature of the polycarbonate membrane results in a fraction of the polyaniline growing in an ordered and compact fashion along the walls of the pore. The switching properties of polyaniline grown into such pores changes significantly when the polycarbonate membrane is treated with a surfactant like Triton X 100. The polyaniline obtained in this case is largely disordered and open, with room for changes in conformation. This disordered material therefore shows larger changes in conductivity, about a factor of 10(2) larger, than the ordered material on switching from insulating to conducting state.