Low-Frequency Sub-0.5 mm Magnetoelectric Antenna for Wireless Power Harvesting in Injectable Deep-Tissue Implants

Wireless battery-free implants can harvest power from externally applied waves, yet powering deep-tissue implants remains complex. Although optical waves undergo absorption in dense tissue structures and acoustic waves encounter interference from impedance mismatch, kilohertz radio frequency (RF) waves achieve superior tissue penetration. However, miniaturizing RF antennas is challenging. Our study introduces a solution via an ultraminiaturized magnetoelectric (ME) antenna, $\mathrm {\mathbf {200 }} {\mu }\mathbf {m}$ in diameter, operating at the low-frequency (LF) band. This antenna relies on the ME effect, converting incident magnetic waves into electric charges through a mechanical coupling between magnetostrictive (MS) and piezoelectric (PE) thin films of 250 nm in thickness. Our device has an ME coupling coefficient of $\mathrm {\mathbf {768 V\cdot }}{\mathbf {cm}}^{\mathrm {\mathbf {-1 }}}\mathbf {O}\mathbf {e}^{\mathbf {-1}}$ at 109.3 kHz, showcasing its efficacy even in regions deep inside the body. Moreover, our device fabrication is VLSI-compatible, promising potential integration with CMOS circuitry and positioning it as a prospective frontrunner for minimally invasive bioelectric applications.