ELECTROMAGNETIC COMPATIBILITY AND RENEWABLE POWER FOR IMPLANTABLE NEUROSTIMULATORS
Over the last decade, the number of implantable neurostimulator systems implanted in patients has been rapidly growing. Nearly 50,000 neurostimulators are implanted worldwide annually. The most common type of implantable neurostimulators is indicated for pain relief. At the same time, commercial use of other electromagnetic technologies is expanding, making electromagnetic interference neurostimulator function an issue of concern. The susceptibility of six active implantable neurostimulators with lead systems to an electromagnetic field generated by 22 radio frequency identification emitters was investigated. It was found that one implantable neurostimulation system was inhibiting the stimulation pulse during low frequency exposure at close distances. To systematically address the concerns posed by EMI, a test platform was developed to assess the interference from coupled magnetic fields on implantable neurostimulator systems. The lifetime of any active neurostimulator system heavily depends on its battery. Current technology has been able to provide solutions to power up such devices for up to five years. In fact, the latest research in this area showed that, on average, batteries last only three years. When an implantable battery needs to be replaced, a surgical procedure is required during this process. In addition, the current available implantable batteries contain potentially hazardous materials to human bodies and if leaked could cause potentially lethal complications. A system was developed that demonstrates a proof of concept based on cascaded concentration cells that can currently deliver 2 µW of power, capable of powering small scale implantable devices. Ideally, the system could replace or charge an existing battery based on concentration differences that already exist within the human body. The system has several advantages over the current implantable batteries and other proposed technologies. The most important advantage is the use of flexible, biocompatible materials. The system does not use toxic or nuclear materials and does not depend on energy sources outside of the human body or body movement. It does not heat body tissue, or require a cosmetic disadvantage. It makes use of renewable energy sources within the human body.