Multimodal Wireless-Powered Flexible System for Closed-Loop Neuromodulation

This article presents a wirelessly powered closed-loop neuromodulation system, containing both implantable and wearable parts. The implantable part is an implantable neuromodulator tag that contains a customized application specific integrated circuit (ASIC) for neurostimulation and recording, an off-the-shelf near-field communication (NFC) proximity integrated circuit card (PICC) chip, and one coupling coil for communication and power transferring. There is a wireless monitoring device, an NFC reader, electroencephalogram (EEG) electrodes, and near-infrared spectrum (NIRS) modules in wearable part. Intracranial neural recorder and wearable EEG/NIRS modules are able to provide multimodal biological information, such as local field potentials (LFPs), EEG, and cerebral tissue oxygen saturation (StO $_{{2}}{)}$ for algorithms to propose a more precise closed-loop stimulation strategy for better treatment effect. The ASIC chip is fabricated in a 0.18- $\mu \text{m}$ CMOS technology. The stimulator has a limited size of 0.027 mm ² . Its stimulation current ranges from 0 to 0.6 mA with a bandwidth of 10 Hz–8 kHz, which is able to support precise neuromodulation. The recording channel features a bandwidth of 0.5–100 Hz with a noise floor of $0.93 \mu \text{V}_{\text {rms}}$ . The entire neuromodulator tag has a small footprint of $20\times 24\times1.4$ mm, and its weight is only 0.25 g.