Miniature Implantable System Dedicated to Bi-Channel Selective Neurostimulation

This paper concerns the design and implementation of a Bi-channel Selective Neurostimulator (BSN). It is dedicated to demonstrate the efficiency of bilateral sacral roots stimulation during chronic experiments in small animals (rats). The complete BSN implant has been highly miniaturized. It is powered and controlled by an inductive RF link and includes two channels. Even though they are meant for simultaneous operation, the channels outputs are synchronized to avoid drawing high stimulation currents at the same time. In addition, an alternating monophasic stimulation is used to reduce charge injection while keeping the advantage of charge balancing of the biphasic stimulation. The BSN prototype has been assembled on two circular printed circuit boards of 2-cm diameter each. With a total rms power consumption of less than 15mW, the BSN can provide a stimulation current up to 2mA, with maximum pulse width of 210μs and a maximum frequency of 2kHz.