title: Implantable RF power converter for small animal in vivo biological monitoring.
abstract: A miniature, long-term, implantable radio frequency (RF) power converter for freely moving samll animal in vivo biological monitoring is proposed. An environment consisting of a laboratory mouse inside a cage is used for a prototype monitoring system design. By employing an inductive coupling network, a prototype implant device with a dimension of approximately 6 m x 6 mm x 1 mm and a weight of 100 mg including medical-grade silicone coating can wirelessly receive an input FR power from an array of external coils positioned underneath the cage. Each coil is designed to be 5 cm x 5 cm, comparable to a typical mouse size for minimizing power coupling variation. The received AC voltage is further rectified by a half-wave rectivier to supply DC current to a 3 k&#969; resistance, representing a typical bio-implant microsystem loading. The proposed RF power converter was implanted in the peritoneal cavity of a laboratory mouse for performance evaluation. With a 5-turn external coil loop separated from a 30-turn internal coil by 1cm distance and centered to each other, an optimal voltage gain of 3.5 can be achieved with a 10 MHz operating frequency to provide a maximum rectified output DC voltage of 21 V. The DC voltage varies at different animal tilting angles and positions with a minimum voltage of 4 V at 60&#176; tilting angle near the corner of the external coil. This variation can be further minimized by overlapping the external loops layout.
authors.affiliation: School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA, Email: nxc35@case.edu.
authors.forename: Nattapon
authors.initials: N
authors.lastname: Chaimanonart
authors.forename: Keith
authors.initials: K
authors.lastname: Olszens
authors.forename: Mark
authors.initials: M
authors.lastname: Zimmerman
authors.forename: Wen
authors.initials: W
authors.lastname: Ko
authors.forename: Darrin
authors.initials: D
authors.lastname: Young