A Wirelessly Powered, Battery-Less, and Miniaturized Microchip for Implantable Biopotential-Monitoring Applications

This article presents a low-power, battery-less biopotential-recording integrated circuit (IC) designed for implantable leadless cardiac monitoring applications, addressing full autonomy based on wireless energy harvesting and closed-loop control. A key technical feature is the closed-loop capability with integration of a dual-band radio frequency (RF) energy harvester and communication system utilizing industrial, scientific, and medical (ISM) bands at 40.68 MHz for downlink and 915 MHz for uplink, ensuring efficient wireless power transfer and robust bidirectional data communication. The RF harvester achieves a peak conversion efficiency exceeding 40%, a critical design challenge in maintaining consistent performance under variable power conditions. Also, the proposed IC overcomes the need for a local oscillator (LO) by utilizing an externally provided clock, reducing system complexity and power consumption. Operating with a clock frequency of 100 kHz, the IC consumes only $8.8~\mu $ W, a major achievement in energy efficiency for wireless, battery-less systems. Fabricated in a 180-nm complementary metaloxidesemiconductor (CMOS) process, the IC successfully demonstrates cardiac signal measurement and heart rate (HR) extraction under a fully battery-less environment with air medium, providing a promising solution for next-generation leadless cardiac monitoring systems.