Smart internet of things (IoT) sensor nodes require continuous power Mechanical energy can be converted into the electrical energy in daily life. Mechanical energy harvesting can play a critical role for microgrid to operate wireless smart sensor platforms. 

The operating frequency plays a crucial role in determining the energy conversion efficiency of mechanical energy harvesting devices. To achieve continuous and sustainable power supply from irregular motions in nature, we have investigated a mechanical strategy for developing a frequency regulating system that effectively aligns device operation with optimal frequency conditions. 

To design a mechanical conversion system, computer-aided engineering (CAE) and multibody dynamics are essential tools. Finite element method (FEM) simulations serve a pivotal role in constructing a digital twin of the system, enabling accurate representation of its physical behavior. Through CAE analysis, contact forces and torques can be precisely estimated for each model, allowing the system to be optimized under realistic operating conditions. 

In nature, the mechanical energy of water droplets, such as raindrops, can be effectively converted into significant electrical signals through the formation of an electrical double layer (EDL). Consequently, extensive research has been devoted to developing high-performance droplet energy generators, particularly by leveraging advanced surface treatment technologies.