Micro-power implantable telemetry device for the study of micro-package technology for chronic biomedical micro-systems

This paper reports the micro-power telemetry unit that can sense pressure, humidity, and bio-potentials, for the study of micro-package techniques for implantable biomedical micro-systems used in research, diagnosis and therapy. The micro-package study is aimed to develop and demonstrate the micro-package technology for micro-implants to have an implant life of 0.2 to 2.0 years. The telemetry device consumes <; 1.0 μA at 3 volts, with a volume <; 0.2 cm³ including lithium rechargeable battery, and has RF links to charge Li battery and to receive external on-off commands. The device output pulse width changes with a capacitive pressure sensor; and the pulse period changes with an external resistor as the humidity sensor or the bio-potential signals in series with the resistor. The first model of telemetry units, packaged with silicon and epoxy only, lasted more than 70 days in 40°C saline solution. The RF recharging and on-off control circuits was tested, and the lifetime of second generation telemetry unit are being evaluated.