Energy harvesting holds great potential to achieve long-lifespan self-powered operations of wireless sensor networks, wearable devices, and medical implants, and thus has attracted substantial interest from both academia and industry. This paper presents a comprehensive review of piezoelectric energyharvesting techniques developed in the last decade. The piezoelectric effect has been widely adopted to convert mechanical energy to electricity, due to its high energy conversion efficiency, ease of implementation, and miniaturization. From the viewpoint of applications, we are most concerned about whether an energy harvester can generate sufficient power under a variable excitation. Therefore, here we concentrate on methodologies leading to high power output and broad operational bandwidth. Different designs, nonlinear methods, optimization techniques, and harvesting materials are reviewed and discussed in depth. Furthermore, we identify four promising applications: shoes, pacemakers, tire pressure monitoring systems, and bridge and building monitoring. We review new high-performance energy harvesters proposed for each application.

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This paper presents a fully enclosed duck‐shaped triboelectric nanogenerator (TENG) for effectively scavenging energy from random and low‐frequency water waves. The design of the TENG incorporates the freestanding rolling mode and the pitch motion of a duck‐shaped structure generated by incident waves. By investigating the material and structural features, a unit of the TENG device is successfully designed. Furthermore, a hybrid system is constructed using three units of the TENG device. The hybrid system achieves an instantaneous peak current of 65.5 µA with an instantaneous output power density of up to 1.366 W m−2. Following the design, a fluid–solid interaction analysis is carried out on one duck‐shaped TENG to understand the dynamic behavior, mechanical efficiency, and stability of the device under various water wave conditions. In addition, the hybrid system is experimentally tested to enable a commercial wireless temperature sensor node. In summary, the unique duck‐shaped TENG shows a simple, cost‐effective, environmentally friendly, light‐weight, and highly stable system. The newly designed TENG is promising for building a network of generators to harvest existing blue energy in oceans, lakes, and rivers.

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Since their debut in 2012, triboelectric nanogenerators (TENGs) have attained high performance in terms of both energy density and instantaneous conversion, reaching up to 500 W m −2 and 85%, respectively, synchronous with multiple energy sources and hybridized designs. Here, a comprehensive review of the design guidelines of TENGs, their performance, and their designs in the context of Internet of Things (IoT) applications is presented. The development stages of TENGs in large-scale self-powered systems and technological applications enabled by harvesting energy from water waves or wind energy sources are also reviewed. This self-powered capability is essential considering that IoT applications should be capable of operation anywhere and anytime, supported by a network of energy harvesting systems in arbitrary environments. In addition, this review paper investigates the development of self-charging power units (SCPUs), which can be realized by pairing TENGs with energy storage devices, such as batteries and capacitors. Consequently, different designs of power management circuits, supercapacitors, and batteries that can be integrated with TENG devices are also reviewed. Finally, the significant factors that need to be addressed when designing and optimizing TENG-based systems for energy harvesting and self-powered sensing applications are discussed. Integrated Self-Powered Systems