Abstract <p>The rapidly advancing field of piezoelectric and triboelectric nanogenerators (PENG and TENG), which convert mechanical energy into electrical power, is set to play a pivotal role in the age of the Internet of Things, big data, and artificial intelligence. This review provides a critical analysis of material selection processes for TENGs and PENGs, highlighting core principles, key performance metrics, and optimal materials selection/modification to enhance electrical output. Emphasizing an interdisciplinary approach, the review showcases collaborative efforts across materials science, engineering, biology, and environmental science that drive the development of novel materials and fabrication techniques. Innovative approaches to sustain specific environmental challenges, such as extreme temperatures, high humidity, and mechanical stress, are presented. The review also underscores the significance of biocompatibility and biodegradability for medical applications, alongside flexibility and mechanical resilience for wearable electronics and environmental sensors. Future perspectives and emerging materials are discussed, emphasizing the transformative potential of optimized material selection strategies to expand applications in energy harvesting, biomedical devices, and other cutting-edge technologies.</p> Graphical abstract <p></p>