IoMT-Enabled Smart-Cap-Powered Ultrawideband Brain Implant for Multichannel Epilepsy Monitoring Applications

Abstract

Multichannel neural monitoring systems are crucial in the accurate diagnosis and treatment of epilepsy by continuously recording neural activity, allowing precise identification of epileptic zones. These systems demand an ultrawideband (UWB) antenna with wireless power reception capability to facilitate high-data-rate communication and battery-free operation for the development of compact and long-lasting neural devices. This articel introduces a compact ( $9\times 11\times 0$ .25 mm3) battery-free implantable UWB system with an integrated rectifier for multichannel epilepsy monitoring, wirelessly powered by a novel 2.4 GHz smart cap-based transmitter (Tx) antenna. Extensive simulations and measurements are conducted to analyze the system's performance. The implantable system exhibits a measured ultrawide bandwidth of 6.8 GHz (1.2-8 GHz) with peak gain values of -16.5, -23, and -24.1 dBi at 2.4, 4.8, and 5.8 GHz, respectively. The proposed wearable smart cap-based Tx antenna efficiently transfers power to the UWB implant system in various scenarios, including lateral and rotational misalignments, achieving a measured transmission coefficient $(|S_{21}|)$ of -20.06 dB at a 15 mm distance while ensuring user comfort and mobility. Moreover, the compact rectifying circuit achieves a maximum conversion efficiency of 78.4% at a low input power of 6 dBm across a 2 k $\Omega $ load. In addition, the safety of the system was validated using a realistic human head model to ensure compliance with the IEEE specific absorption rate limits. The features and performance metrics demonstrate that the proposed UWB implant system, powered by a wearable smart cap, offers a promising solution for safe, continuous, and battery-free multichannel epilepsy monitoring applications.