The quality of life of patients relying on electrically powered artificial organs is currently restricted by the limited energy availability provided by portable batteries. As these patients become increasingly ambulatory, and are developing more active lifestyles, this limitation grows more apparent. Coincidentally, these patients may themselves be capable of generating electrical power as a consequence of their physical activity. Extraction of this latent autologous energy could, in turn, be used to augment charging of internal batteries—thus untethering the patient from external power for extended periods of time. In this study, the viability of deriving energy associated with natural human ambulation has been evaluated. The kinematic components of gait were evaluated to identify the largest useful forces and moments that may be harnessed as an energy source, while presenting minimal “perceived” work for the patient. It was found that the ground reaction forces associated with the heel strike and toe-off phases of the gait represent the greatest potential for usable energy. This study uses a piezoelectric array within the midsole of the shoe for the conversion of mechanical to electric energy. This power could then be easily coupled in tandem with existing transcutaneous transformers for augmenting or temporarily replacing external power sources.
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