Ionic bipolar transistors can be made from two conical channels with the smallest opening in nano-scaled dimension. By introducing opposite surface charges at each side, it is able to rectify ionic current as an ionic diode. An ionic bipolar transistor is built by combining two ionic diodes and forming a PNP junction along the inner surface of the channel. While the ionic current is from emitter end to collector end, the strength of the current can be modulated by the base electrode. The surface charge at the channel wall can be modified using chemical methods, by changing the electrolyte concentration or pH value.