Most of the emerging electronic devices are wearable in nature. However, the frequent changing or charging the battery of all wearable devices is the big challenge. Interestingly, with those wearable devices that are directly associated with the human body, the body can be used in transferring or generating energy in a number of techniques. One technique is triboelectric nanogenerators (TENG). This chapter covers different applications where the human body is used as a triboelectric layer and as a sensor. Wearable TENG has been discussed in detail based on four basic modes that could be used to monitor the human health. In all the discussions, the main focus is to power the wearable healthcare internet of things (IoT) sensor through human body motion based on self-powered TENG. The IoT sensors-based wearable devices related to human body can be used to develop smart body temperature sensors, pressure sensors, smart textiles, and fitness tracking sensors.
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The current major issues of the world are related to energy transportation, generation, and conservation; moreover, the serious life threating environmental issues are also caused by standard energy resources like nuclear, biomass, and fossil fuels (coal, oil, and natural gas), etc. Implementing stable, enduring and innovative energy policies are crucial for economic and social development globally. Renewable energy technologies such as solar, geothermal and wind energies have an important role in lowering Carbon dioxide CO2 emissions which is the major cause of increased global warming. Therefore, these technologies also known as clean and green energy sources. (Panwar, Kaushik, & Kothari, 2011) On the other hand, with the ever-growing development of nanotechnology-based devices, power consumption is the major issue in these devices(Hussein, 2015; S. Wang, Lin, & Wang, 2015). Moreover, self-powered and sustainable devices are more popular than systems with standard batteries. At the smaller scale, energy is required to power small electronics that should be self-powered, wireless, and maintenance-free for the small sensor networks, that is known as the Internet of Things (IoT) (Gope & Hwang, 2016; Saravanakumar et al., 2015; Sodhro, Pirbhulal, Luo, & de Albuquerque, 2019). Reduction in the size of microprocessor, sensor, and even portable/wearable personal small electronic devices are the main reason for the self-powered systems(A. Ali, Hwang, Choo, & Lim, 2018a). In the near future, these devices can modify the method tend to control the air/water quality, environmental conditions, organic structure, and structural health. However, because sensors and devices are increasing day by day, there is a huge challenge of powering these devices and sensors. (Lara & Labrador, 2013). Figure 1 shows an overview of wearable and flexible health-monitoring sensors to detect physical activity and a variety of biosignals from the human body as well as user interaction and communication systems for practical applications. (Ha, Lim, & Ko, 2018). The human body generates different types of signals they are categorized here in main three signals i-e Physical signals (pressure, motion, tactile and vibration), thermal signals which are (fever and hypothermia) and Electrophysiological signals (Brain wave, cardiac activity, and muscle movement). Figure 1 illustrates the different sensors are attached to the human body like a smartwatch, smart textile, smart band, thermometer, electroencephalogram (EEG), electromyography (EMG), and electrocardiogram ECG. These all sensors are connected to the user interactive system via wireless communication systems like Bluetooth, near-field communication (NFC) and radio-frequency identification (RFID). The user interactive system contains remote medical services, self-diagnosis, and healthcare. Over the years, great developments have been made in nanofabrication with different functionalization and integration, in addition to that great cutting edge materials have been prepared with skin-like properties like, flexibility/elasticity and stretchability for empowering wearable devices (A. Ali, Hwang, Choo, & Lim, 2018b; Rogers, Someya, & Huang, 2010). Therefore, together with the Internet of Things (IoT), and Artificial Intelligence, wearable devices have been growing day by day. The worldwide market of wearable devices innovation is expected to grow over $150 billion by 2026 and predicted to develop at a yearly rate of 23% from 2019 to 2023(X.-S. Zhang et al., 2018). Broadly speaking wearable devices are practically applicable to every field of life, from individual wellbeing to versatile correspondence, personalized medicines, security, safety, and numerous other areas. However, there are some challenges that need to be addressed for any practical application. The first major challenge is how to power the wearable device for a long period of time, the other issues are related to biocompatibility and ergonomics(Miotto, Wang, Wang, Jiang, & Dudley, 2017; Sodhro, Li, & Shah, 2016). For power batteries are the classical choice, however, they suffer from many problems such as, constantly recharging, limited life and the replacement with the time.