Real-Time Frequency Tuning of Kinetic Energy Harvesters via System Mass Adjustment

This research presents a method for real-time frequency tuning of piezoelectric kinetic energy harvesters through system-mass adjustment. Custom 3D-printed proof masses with cavity arrays were used to redistribute solid or liquid mass, enabling controlled modification of resonant frequency. Experimental studies using microparticles and liquids—including water, silicone oil, and sodium polytungstate—demonstrated an achievable tuning range of 115. 27 Hz with sub-hertz resolution (< 0. 1 Hz), confirming precise and repeatable frequency control. Finite-element modeling guided design optimization, while a microfluidic channel system enabled automated liquid filling for real-time operation. A MATLAB-based EHTuning application was developed to visualize and predict frequency responses. The combined computational and experimental results establish a scalable, energy-efficient approach for adaptive piezoelectric harvesters suited for Internet of Things and wireless sensor network applications.