A Metglas-Based Magneto-Triboelectric Energy Harvesting Device for Biomedical Applications

This work proposes a Metglas-based magneto-triboelectric energy harvesting device capable of harvesting energy from both external magnetic fields and mechanical motion. This study particularly focuses on investigating the origin of triboelectric properties in Metglas which is well-known for its giant magnetostrictive nature in various applications. We studied the variation in contact electrification capabilities of commercial Metglas under pristine and elevated temperature annealed conditions, where pristine Metglas demonstrates positive triboelectrification, while annealed Metglas exhibits negative triboelectric properties. With thermal annealing at $500~^{\circ } $ C, the electron affinity of pristine Metglas is observed to increase due to microstructural changes, resulting in a switch in its triboelectric polarity. To employ the unique dual triboelectric properties of Metglas in the application, two hybrid devices consisting of Metglas and PTFE, and annealed Metglas and glass, as triboelectric layers are fabricated. Electromechanical characterization of the two hybrid devices reveals that with an applied pressure of 60 kPa, a peak power of 0.75 and $0.9~\mu $ W are generated, respectively. Due to the inherent magnetostrictive property of Metglas, 2.67 times and 3.67 times improvement in output are observed for the two devices by applying an external magnetic field of 0.4 T in addition to the applied mechanical pressure. Furthermore, the robustness of the devices is confirmed by continuous tapping for five consecutive days, resulting in a maximum variation in output voltage of 4%–6%. Due to the unique working principle of the magneto-enhanced triboelectric device, it can have significant usefulness in wearable and biomedical devices.