When it comes to implantable electronic devices such as pacemakers, biosensors or drug-delivery devices, there are a few options regarding power sources. While batteries could be used in some applications, doing so would require surgically replacing the implant when its battery runs out. Radio wave-based and inductive systems are instead often used, in which power is “beamed” to the device from a source outside the body. According to researchers from Germany’s Fraunhofer Institute for Ceramic Technologies and Systems, however, such systems often have a limited range, and are easily affected by factors such as location, position and movement. Instead, they’ve developed what they claim is a better, more versatile system.
The setup consists of an external transmitter module and a mobile generator module – the generator is part of the implant. The transmitter has a range of about 50 centimeters (20 inches), so it could be worn on the user’s belt or another location on their body.
An electric motor in the transmitter causes a magnet to rotate inside the device, generating a magnetic rotary field. This field can harmlessly travel through human tissue, along with virtually any other non-magnetic material. The generator contains a magnetic pellet, which is set in rotation in response to the transmitter’s magnetic field. Its spinning movements are used to generate electricity, right within the module itself. That electricity in turn powers the implant.
Along with providing power, the transmitter could also be used to pinpoint the location and movements of the generator. This could come in handy if the generator were on a video camera-equipped endoscopic capsule, for instance, as its transmitted images could be matched to specific locations within the intestinal tract.
Because the magnetic field can travel through so many types of material, scaled-up versions of the system could conceivably also be used to power hermetically sealed sensors inside walls or bridges, or to otherwise wirelessly deliver power to unreachable electronic devices.
A prototype of the system is currently in use on a hip implant, in which electrical pulses are being used to stimulate cartilage and bone growth. Other institutions are looking into implants that could draw their power from within the body, via glucose and oxygen, or even the beating of the heart.