Two significant problems are present which impede the widespread utilization of many implantable devices with great potential: 1) the lack of availability of an efficient energy source suitable for long-term operation, and 2) the lack of a robust, low-power communication path which does not rely on wired connectivity. The creation of a feasible solution to these two power and communication issues is critical to the success of many future implantable devices. This foundational work details the development of a general solution for the above issues, in a power and communications platform technology for implantable devices. The platform is developed based on the volume conduction technology explored in our laboratory. Ultimate devices are small in size, with the incorporation of a rechargeable battery and electrodes used for interfacing with external components through the skin. An external patch, or "energy pad," containing low-profile electrodes and circuitry, is used as the external interface for recharging and communicating with implanted devices. System design focuses on reliability and ease of integration into a variety of implantable systems, making them feasible for clinical application. Because this is the first system that uses volume conduction for both power and communication purposes, a novel "X-Δ model" of the system is created for use in analyzing the energy transfer of such systems to assist in engineering design. The model, which incorporates components to represent actual current pathways in the skin, is also used in finding theoretical maximum limits of volume conduction energy transfer efficiency for specific skin-electrode setups, proving the technology as a viable option for practical implanted devices.
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