An impact sensing platform for spinal cord injury experiments

Real-time measurement of rat/guinea pig spinal cord mechanics during ex vivo experiments remains a nontrivial task due to the small size of the cord and the short impulse duration. To address this issue, we present an inexpensive strain measurement platform. It consists of an array of flexible, Parylene-C-passivated, pointed cantilevers of polyvinyl fluoride (PVDF) that penetrate the wall of an acrylic chamber. When a spinal cord is placed in the chamber and stimulated mechanically, its vibrations translate onto the PVDF cantilevers which in turn generate an electrical signal for recording. Vibrometer experiments of the cantilever reveal a deflection of up to 58 nm at its resonant frequency (~50 kHz). Voltage from a cantilever in a cord phantom has been recorded at two distances from the point of impact, showing 37 mV at 5 mm and 21 mV at 20 mm for a 40 kPa impact pressure.