Research Progress of Acoustic Energy Harvesters Based on Nanogenerators

In the wake of the rapid development of the Internet of Things (IoT) and artificial intelligence (AI) technology, a huge amount of wireless sensing nodes (WSNs) is urgently in demand in all aspects of daily production and living, such as smart cities, smart transportation, and intelligent monitoring. However, it has become one of the crucial challenges in the development of IoT technology to fulfill the requirements of energy consumption for enormous amounts of WSNs. Therefore, it not only possesses great potential to realize in situ power supply of WSNs by harvesting environmental energy but also can address the problems of durability, maintenance, and cost that exist in battery power supply. In particular, acoustic energy is ubiquitous in the environment but not efficiently utilized. Meanwhile, piezoelectric nanogenerators (PENG) and triboelectric nanogenerators (TENG) are capable of accomplishing efficient conversion of broadband, high entropy, and weak energy as the new energy conversion technology. Therefore, the basic principle of acoustic energy harvester based on nanogenerators (NGs) is firstly discussed. Then, the advances of acoustic energy harvesters based on NGs in the viewpoint of acoustic energy resonator structures are systematically reviewed for the first time. This review not only covers the working mechanism, structural design, and application scenarios of acoustic energy harvesters but also explores the advances in ultrasonic energy harvesting based on NGs. Finally, existing challenges and prospects for future development are systematically discussed, which will facilitate the development of acoustic energy harvesting based on NGs.