Fig. 6From: Development of a battery-free ultrasonically powered functional electrical stimulator for movement restoration after paralyzing spinal cord injuryExperimental setup for in vivo stimulation. A 1 MHz sinusoidal signal was amplified to drive the external ultrasound probe. The ultrasound signal captured by the implanted piezoelectric stimulator to stimulate hindleg muscles. Force exerted by the muscle contraction was captured by a custom force sensor and then amplified and digitized for display on a computer screenBack to article page