title: Inductive and ultrasonic multi-tier interface for low-power, deeply implantable medical devices.
abstract: We report the development of a novel multi-tier interface which enables the wireless, noninvasive transfer of sufficient amounts of power as well as the collection and transmission of data from low-power, deeply implantable analog sensors. The interface consists of an inductive coupling subsystem and an ultrasonic subsystem. The designed and experimentally verified inductive subsystem ensures that 5 W of power is transferred across 10 mm of air gap between a single pair of PCB spiral coils with an efficiency of 83% using our prototype CMOS logic gate-based driver circuit. The implemented ultrasonic subsystem, based on ultrasonic PZT ceramic discs driven in their low-frequency, radial/planar-excitation mode, further ensures that 29 μW of power is delivered 70 mm deeper inside a homogenous liquid environment-with no acoustic matching layer employed-with an efficiency of 1%. Overall system power consumption is 2.3 W. The implant is intermittently powered every 800 msec; charging a capacitor which provides sufficient power for a duration of ~ 18&nbsp;msec; sufficient for an implant μC operating at a frequency of 500 KHz to transmit a nibble (4 bits) of digitized sensed data.
authors.affiliation: Electrical and Electronic Engineering Department, Centre for Bio-inspired Technology, Imperial College London, South Kensington Campus, London SW7 2AZ, UK. a.sanni08@imperial.ac.uk
authors.forename: Ayodele
authors.initials: A
authors.lastname: Sanni
authors.forename: Antonio
authors.initials: A
authors.lastname: Vilches
authors.forename: C
authors.initials: C
authors.lastname: Toumazou
mesh_terms: D001698:Biomedical Engineering; D003201:Computers; D011211:Electric Power Supplies; D004581:Electronics; D004867:Equipment Design; D006801:Humans; D019736:Prostheses and Implants; D012815:Signal Processing, Computer-Assisted; D012867:Skin / Q000473:pathology; D014465:Ultrasonics; D059015:Wireless Technology