Designing piezo- and pyroelectric energy harvesters

The recent development of the "Internet of Things" suggests the growing importance of the development, integration, and system design of multifaceted wearable devices. The demand for maintenance free, clean, and green renewable energy sources with recharging options, which are independent of weather conditions and fossil fuels and which provide long-term energy supply is becoming more and more urgent. Piezo- and pyroelectric nanogenerators have been demonstrated to have excellent potential to harvest electricity from ubiquitous and abundant mechanical and thermal motions respectively. In this chapter, ongoing advances in nanogenerators based on piezo-, pyroelectricity, and hybrid mechanisms are introduced and discussed from the perspective of material selection, geometrical features, and device design configuration. In addition, future strategies and possibilities of this technology are also concisely discussed.