Triboelectric nanogenerators (TENGs) have attracted much attention because they not only efficiently harvest energy from the surrounding environment and living organisms but also serve as multifunctional sensors toward the detection of various chemical and physical stimuli. In particular, biodegradable TENG (BD-TENG) represents an emerging type of self-powered device that can be degraded, either in physiological environments as an implantable power source without the necessity of second surgery for device retrieval, or in the ambient environment to minimize associated environmental pollution. Such TENGs or TNEG-based self-powered devices can find important applications in many scenarios, such as tissue regeneration, drug release, pacemakers, etc. In this review, the recent progress of TENGs developed on the basis of biodegradable polymers is comprehensively summarized. Material strategies and fabrication schemes of biodegradable and self-powered devices are thoroughly introduced according to the classification of plant-degradable polymer, animal-degradable polymer, and synthetic degradable polymer. Finally, current problems, challenges, and potential opportunities for the future development of BD-TENGs are discussed. We hope this work may provide new insights for modulating the design of BD-TNEGs that can be beneficial for both environmental protection and healthcare.

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There is an increasing need for structural flexibility in self-powered wearable electronics and other Internet of Things (IoT), where adaptable triboelectric nanogenerators (TENGs) play a key role in realizing the true potential of IoT by endowing the latter with self-sustainability. Thus, in this review, the topic was restricted to the adaptive design of TENGs with structural flexibility that aims to promote the sustainable operation of various smart electronics. This review begins with an emphatical discussion of the concept of flexible electronics and TENGs, and continues with the introduction of TENG-based self-powered intelligent systems while placing the emphasis on self-powered flexible intelligent devices. Self-powered healthcare sensors, e-skins, and other intelligent wearable electronics with enhanced intelligence and efficiency in practical applications due to the integration with TENGs are illustrated, along with an emphasis on the design strategy of structural flexibility of TENGs and the associated integration schemes. This review aims to cover recent achievements in the field of self-powered systems, and provides information on how flexibility or adaptability in TENGs can be adopted, their types, and why they are required in promoting advanced IoT applications with sustainability and intelligence algorithms.

Currently, significant advances have been made in the field of high-performance energy storage technologies, such as Li-ion batteries and supercapacitors. However, the limited lifespans, as well as the frequent charging or replacement requirements, pose a set of challenges for their application in the Internet of things (IoTs), because the full power of the IoTs can only be realized by the sustainable operation of physical objects, especially embedded sensors, for the purpose of connecting and exchanging data with other devices and systems continually in real-time. A viable option for achieving the sustainability of the IoTs may be the combination of renewable energy harvesting technologies such as triboelectric nanogenerators (TENGs) with electrochemical energy storage technologies, where TENGs can harvest mechanical energies from ambient environments and transform them into electricity for charging electrochemical batteries and supercapacitors (SCs) conveniently, thus developing a new type of TENG-based uninterrupted power supply (TENG-UPS). In this review, we begin from a brief description of the operating mode of TENG and the integration strategy of TENG-UPS. The latest advances in the TENG-UPS are then thoroughly discussed from the perspective of structural design and system integration. Cutting edge developments of the as-designed self-powered sensing systems are then concisely illustrated to disclose the application potential in the IoTs. The main obstacles and future prospects for developing TENG-UPS-based intelligent systems are also highlighted in terms of design and manufacture at the conclusion. We expect this review will appropriately shine a light on the understanding of the key role of electrochemical energy storage devices in the development of TENG-based energy harvesting technology as well as the self-powered intelligent systems.

Nowadays, self-powered wearable biosensors that are based on triboelectric nanogenerators (TENGs) are playing an important role in the continuous efforts towards the miniaturization, energy saving, and intelligence of healthcare devices and Internets of Things (IoTs). In this review, we cover the remarkable developments in TENG−based biosensors developed from various polymer materials and their functionalities, with a focus on wearable and implantable self-powered sensors for health monitoring and therapeutic devices. The functions of TENGs as power sources for third-party biosensors are also discussed, and their applications in a number of related fields are concisely illustrated. Finally, we conclude the review with a discussion of the challenges and problems of leveraging TENG−based intelligent biosensors.