Freestanding Graphene Variable Capacitors for Vibration Energy Harvesting

This study focuses on enhancing the capacitance of freestanding graphene-based variable capacitors for vibration energy harvesting. We first developed a scalable fabrication process using a two-step lithography technique, successfully integrating arrays of capacitors on 20mm x 20mm silicon wafers. In the first step, long trenches terminated by square wells are created, and in the second step, metal traces are formed from each well to its contact pad along the trench and a second contact pad opposite the square well. Building on this foundation, we investigated design optimizations, including increasing the capacitor size and reducing the distance between the graphene membrane and underlying gold plates. These modifications aim to improve device performance by increasing the surface area and enhancing the electric field strength, resulting in higher capacitance values. The fabricated devices were characterized using atomic force microscopy, optical microscopy, and capacitance measurements, demonstrating the potential for improved vibration-based energy harvesting and sensing applications.