Recent Advances in Nanomaterial-Based Flexible Piezoresistive Sensors for Robotic Tactile Sensing
The expansion of industrial automation has underscored the critical role of robotic systems, where pressure sensors serve as essential interfaces for tactile feedback and precise manipulation. Flexible piezoresistive pressure sensors have become especially attractive because of their simple design, straightforward operation, and scalable fabrication. Recent progress in conductive nanomaterials such as carbon- and metal-based fillers, and engineered microstructures, including surface and porous designs in both single and hierarchical configurations, has significantly improved sensor sensitivity and broadened their operational range, demonstrating how material choice and structural engineering directly shape device performance. This review introduces the underlying physics of piezoresistivity and discusses the metrics commonly used to characterize sensor behavior, including sensitivity, gauge factor, and response time, before examining advances in nanomaterial integration and structural strategies that enable enhanced functionality. Applications highlight their integration into robotic fingertips and joints, where they provide force regulation, object recognition, and motion tracking, underscoring their importance in robotic control. Remaining challenges such as uniformity, reproducibility, and large-scale manufacturability continue to hinder widespread adoption, yet ongoing improvements in material systems and fabrication methods promise to address these limitations. Through the integration of material design, structural engineering, and performance evaluation, this work establishes a comprehensive link between fundamental principles and robotic applications, offering insights that can guide the development of next-generation tactile sensing technologies and opening pathways toward next-generation robotic systems empowered by highly sensitive and reliable pressure sensors.