Sustainable Energy Harvesting in IoT Devices: A Review of Piezoelectric and Triboelectric Nanogenerators

Abstract

Internet-of-Things (IoT) deployments now span wearables, smart infrastructure, biomedical implants and industrial monitoring—yet they still rely heavily on batteries that add cost, maintenance overhead and e-waste. Piezoelectric and triboelectric nanogenerators (PENGs and TENGs) have emerged as ultra-compact transducers that convert ubiquitous mechanical vibrations, bending, pressure, acoustic waves and even raindrops into usable electrical energy. In the past five years both technologies have matured from laboratory curiosities to components integrated in commercial sensor nodes and printed circuit boards. This review critically surveys the state of the art in nanogenerator-powered IoT, beginning with fundamental transduction mechanisms and moving through materials engineering, device architectures, power-management circuits and real-world case studies. Market intelligence reveals a nanogenerator industry worth USD 39.5 billion in 2024 and projected to exceed USD 84 billion by 2033, while the population of connected devices will surpass 25 billion in 2025, underscoring the urgency of self-powered designs. We analyse benchmark figures-of-merit—open-circuit voltage, current density, power density and mechanical robustness—across leading material systems such as ZnO, BaTiO₃, PVDF, PTFE, MXenes and cellulose nanofibrils. Integration strategies, including hybrid PENG–TENG stacks, micro-supercapacitor buffering and MPPT-enabled power-conditioning ASICs, are compared. Finally, we map outstanding challenges—fatigue under cyclic strain, charge leakage, standardised testing, cybersecurity of energy-harvesting nodes and end-of-life sustainability—and outline future research vectors such as stretchable 3-D printed nanogenerators and AI-assisted topology optimisation.