Miniaturized Wirelessly Powered and Controlled Implants for Multisite Stimulation

Abstract

This article presents a miniaturized implant with a diameter of only 14 mm, which houses a novel system on chip (SoC) enabling two-voltage-level stimulation of up to 16 implants using a single transmitter (Tx) coil. Each implant can operate at a distance of 80 mm in the air through the inductive resonant link. The SoC consumes only 27- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> static power and enables two channels with stimulation amplitudes of 1.8 and 3.3 V and a timing resolution of 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> . The SoC is implemented in the standard 180-nm complementary metal–oxide–semiconductor (CMOS) technology and has an area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.75\times1.6$ </tex-math></inline-formula> mm. The SoC comprises an RF rectifier, low dropout regulator (LDO), error detection block, clock data recovery, finite-state machine (FSM), and output stage. Each implant has a printed circuit board (PCB)-defined passcode, which enables the individual addressability of the implants for synchronized therapies. The implantable device weighs only 80 mg and sizes 20.1 mm3. Tolerance of up to 70° to angular misalignment was measured at a distance of 50 mm. The efficacy of bilateral stimulation was further verified by implanting two devices on two sides of a pig’s neck and performing bilateral vagus nerve stimulation (VNS) while monitoring the heart rate.