Abstract: A mechanism to harvest the mechanical energy available during prosthetic leg use for the purpose of charging an electric battery operating a vacuum pump for a prosthetic leg residual limb mounting socket is disclosed. The present invention is intended to be applied with variations of leg prostheses equipped with prosthetic feet constructed with flexible heel and/or forefoot members in the sole. The present invention utilizes one or more electric generators to convert the mechanical energy occurring as bidirectional movement in the foot sole flexible members to electrical energy. The electrical energy is harvested by storage in capacitors, then subsequently used to charge the vacuum pump battery. The objective is to extend the useful operating time of the vacuum pump supporting vacuum socket mounting of the residual limb.