Biomedical Implants require a clean and medically safe source of energy to perform their operations. Early implants such as pacemakers sourced their power from small lithium ion batteries. While this solution allows for the operation of the implantable device without a wire connecting the internal and external circuitry, limited battery life causes the impracticality, health risks and expense of operating on patients for the mere purpose of replacing the battery. The use of wireless power technology in implantable devices led to a more flexible range of applications which were not otherwise possible.