An ultrasonically controlled switching system for power management in implantable devices

In this paper, we present an ultrasonically controlled switching system that can save the battery power for implantable devices by turning the system on and off, on-demand. Ultrasonic control is employed to reduce the device size, increase the penetration depth, and reduce misalignment sensitivity associated with alternative techniques using permanent magnet and RF signal. As a proof-of-concept demonstration, a 665 kHz ultrasonic signal is used to activate a piezoelectric receiver which in turn switches a battery-powered RF system on-and-off. In-vitro tests show a reliable switching functionality at distances of up to 8 cm while consuming 43.5 nW (14.5 nA current consumption with 3 V power supply) when the system is in off-state, a factor of 10–100 times lower than the sleep-mode power consumption of typical RF SoC systems. The dimension of fabricated prototype is 6.3 × 16.7 × 2‍ mm 3 allowing it to be easily incorporated into many existing implantable devices.