BIOMEDICAL ENGINEERING

Abstract: There are approximately 11,000 new cases of spinal cord injury (SCI) each year in the United States resulting in impairment of various functions. Implantable functional electrical stimulation (FES) devices are able to restore some function after SCI through artificial electrical stimulation of the nervous system. FES devices require electrical power for operation obtained from either batteries implanted along with the device or from external transcutaneous power sources. Replacement of depleted batteries requires frequent, costly surgeries with increased risk of complications. Transcutaneous power sources have external equipment that can be damaged, are burdensome to carry, are cosmetically unappealing and cannot be used in a wet environment. Under development is an implantable piezoelectric generator driven by electrically activated muscle as a self-replenishing power source that could augment or replace FES power systems. The generator concept is based upon the hypothesis that more electrical power can be generated from stimulated muscle than is needed for muscle stimulation, which has not been previously demonstrated. With such a generator, the lifetime of implanted batteries could be extended, reducing or possibly eliminating replacement surgeries. Internally generated power could allow for periods of FES use without external transcutaneous power system equipment during which a shower or other types of daily activities could be performed independently. A software model of the concept was developed, mechanical testing was performed to verify the accuracy of the model and software simulations were performed to predict output power and to define system parameters. The predicted output power was compared to the theoretical power necessary for muscle stimulation. Results demonstrated the feasibility of the concept. A prototype generator system, including a low power stimulator, piezoelectric material within a mechanical holding device and load circuitry was built based on the software simulation results. Generator operation was demonstrated with rabbit quadriceps muscle in acute animal experiments.

Host: Kenneth Gustafson, Ph.d.