Powering biomedical devices with body motion.

Energy harvesting from body motion is an alternative power source that can be used to energize miniature electronic biomedical devices. This technology can make it possible to recharge batteries to reduce the frequency of or eliminate surgeries to replace depleted cells. Power availability evaluation from walking and running at several body locations and different speeds is presented. Treadmill tests were performed on 11 healthy subjects to measure the accelerations at the ankle, knee, hip, chest, wrist, elbow, upper arm, and side of the head. Power was estimated from the treadmill results since it is proportional to the acceleration magnitudes and the frequency of occurrence. Available power output from walking was found to be more than 0.5 mW/cm(3) for all body locations while being more than 10 mW/cm(3) for the ankle and knee. Running results were at least 10 times higher than those from walking. An axial flux miniature electric dynamo using electromagnetic induction was evaluated for power generation. The device was composed of a rotor with multiple-pole permanent magnets positioned on an annular ring having an eccentric mass, and stacked planar coils as a stator. A 2 cm(3) prototype was found to generate 117 microW of power from the generator placed laterally on the ankle while walking.

Body motion for powering biomedical devices.

Kinetic energy harvesting has been demonstrated as a useful technique for powering portable electronic devices. Body motion can be used to generate energy to power small electronic devices for biomedical applications. These scavengers can recharge batteries, extending their operation lifetime or even replace them. This paper addresses the generation of energy from human activities. An axial flux generator is presented using body motion for powering miniature biomedical devices. This generator presents a gear-shaped planar coil and a multipole NdFeB permanent magnet (PM) ring with an attached eccentric weight. The device generates energy by electromagnetic induction on the planar coil when subject to a changing magnetic flux due to the generator oscillations produced by body motion. A 1.5 cm(3) prototype has generated 3.9 microW of power while walking with the generator placed laterally on the ankle.