Fig. 1

Schematic diagram of the piezoelectric stimulation (pES) experiment setup. The setup includes an external ultrasound energy transmitting system and implanted receiving and piezoelectric current generation module. A signal generator produces 200 μs bursts (1 MHz carrier frequency) of sinusoidal signal and feeds it into a power amplifier to drive an ultrasound probe to produce acoustic energy. With the aid of ultrasound gels, the acoustic energy was then transferred through the skin and was received by the piezostimulator implant. The implant contained a rectifier and filter circuit to convert the sinusoidal piezoelectric signal into a monophasic stimulation pulse for pES. This pES pulse was then delivered to the lumbosacral spinal cord (L2 and S1 levels) via Teflon-coated stimulation wires to activate the neural circuits