Magnetically-powered implantable Doppler blood flow meter

Implantable active devices use batteries for power, requiring expensive and unwieldy metal enclosures. Some such devices are re-charged via magnetic fields, but require external coils to be close to and well aligned with internal coils. We show here a different method: powering a device using segmented Helmholtz coils, allowing much greater leeway in internal coil location; and transmitting magnetically wide-bandwidth data. A proof-of-concept experiment demonstrates practicality.