A Miniature Batteryless Bioelectronic Implant Using One Magnetoelectric Transducer for Wireless Powering and PWM Backscatter Communication

TL;DR

This work tackles the challenge of wireless powering and bidirectional telemetry for millimeter-scale bioelectronic implants by leveraging magnetoelectric (ME) transduction. It introduces a pulse-width modulated (PWM) ME backscatter uplink enabled by a switched-capacitor energy extraction (SCEE) interface and a high-order ME impedance model to capture multi-mode dynamics. The authors demonstrate a mm-scale implant with an integrated SoC and a portable transceiver, achieving 17.73 kbps uplink, 0.9 pJ/bit energy, BER below 1e-4 at several centimeters, and continuous wireless LFP recording in vitro. The combination of SCEE-driven PWM, high-order transducer modeling, and low-power peak detection enables efficient, low-disturbance wireless communication essential for next-generation bioelectronic implants with reduced form factor and improved safety and reliability.

Abstract

Wireless minimally invasive bioelectronic implants enable a wide range of applications in healthcare, medicine, and scientific research. Magnetoelectric (ME) wireless power transfer (WPT) has emerged as a promising approach for powering miniature bio-implants because of its remarkable efficiency, safety limit, and misalignment tolerance. However, achieving low-power and high-quality uplink communication using ME remains a challenge. This paper presents a pulse-width modulated (PWM) ME backscatter uplink communication enabled by a switched-capacitor energy extraction (SCEE) technique. The SCEE rapidly extracts and dissipates the kinetic energy within the ME transducer during its ringdown period, enabling time-domain PWM in ME backscatter. Various circuit techniques are presented to realize SCEE with low power consumption. This paper also describes the high-order modeling of ME transducers to facilitate the design and analysis, which shows good matching with measurement. Our prototyping system includes a millimeter-scale ME implant with a fully integrated system-on-chip (SoC) and a portable transceiver for power transfer and bidirectional communication. SCEE is proven to induce >50% amplitude reduction within 2 ME cycles, leading to a PWM ME backscatter uplink with 17.73 kbps data rate and 0.9 pJ/bit efficiency. It also achieves 8.5 x 10 -5 bit-error-rate (BER) at a 5 cm distance, using a lightweight multi-layer-perception (MLP) decoding algorithm. Finally, the system demonstrates continuous wireless neural local-field potential (LFP) recording in an in vitro setup.

Figures (29)

• Figure 1: Conceptual diagram of a magnetoelectric (ME) implant using a single ME transducer for power and bidirectional data transfers.
• Figure 2: Existing uplink technologies for ME implants, including (a) the hybrid scheme charthad_mm-sized_2015; (b) active driving of an ME transducer hosur_short-range_2023hosur_magsonic_2023; (c) ME backscatter with load-shift-keying yu_wireless_2022.
• Figure 3: Principle and waveforms of the proposed PWM ME backscatter.
• Figure 4: (a) electrical and (b) simplified impedance model of a ME transducer.
• Figure 5: Impedance fitting of an ME film and the corresponding model parameters, where $f_{sc}$ and $f_{oc}$ are the short-circuit and open-circuit resonance frequency calculated from the impedance model parameters.