Textbook in PDF format This book provides a combined effect and an in-depth exploration of how advanced materials and energy-harvesting technologies create smarter and more adaptive sensing device. Self-powered gas sensors have become a cornerstone of modern technological innovation, finding critical utilities in various sectors ranging from medical and environmental monitoring to industrial safety and smart agriculture. The future demands of gas sensors not only depend on its efficiency and sensitivity but also lie in the fabrication of devices that are flexible, environmental friendly, and self-powered