Flexible piezoresistive strain sensors have received significant attention due to their diverse applications in monitoring human activities and health, as well as in robotics, prosthetics, and human–computer interaction interfaces. Among the various flexible sensor types, those with microstructure designs are considered promising for strain sensing due to their simple structure, high sensitivity, extensive operational range, rapid response time, and robust stability. This review provides a concise overview of recent advancements in flexible piezoresistive sensors based on microstructure design for enhanced strain sensing performance, including the impact of microstructure on sensing mechanisms, classification of microstructure designs, fabrication methods, and practical applications. Initially, this review delves into the analysis of piezoresistive sensor sensing mechanisms and performance parameters, exploring the relationship between microstructure design and performance enhancement. Subsequently, an in-depth discussion is presented, focusing on the primary themes of microstructure design classification, process selection, performance characteristics, and specific applications. This review employs mathematical modeling and hierarchical analysis to emphasize the directionality of different microstructures on performance enhancement and to highlight the performance advantages and applicable features of various microstructure types. In conclusion, this review examines the multifunctionality of flexible piezoresistive sensors based on microstructure design and addresses the challenges that still need to be overcome and improved, such as achieving a wide range of stretchability, high sensitivity, and robust stability. This review summarizes the research directions for enhancing sensing performance through microstructure design, aiming to assist in the advancement of flexible piezoresistive sensors.

Smart sensors are becoming one of the necessities for connecting and detecting surrounding stimuli with tremendous convenience, especially when exploiting a single powerful sensor with multifunctionality. To successfully accomplish the design of a self-powered sensor, serving power is becoming a critical issue because of its continuously consumed energy required by electronics. A variety of nanogenerators aiming for the rational design of self-powered system are reviewed and compared, followed by their recent advances with polymer nanocomposites for self-powered sensors. More importantly, the proposed conceptual design of a self-powered unit/device with triboelectric nanogenerator has been emphasized to eventually realize the practical activities towards multiple detections and human–machine interaction. Finally, challenges and new prospects of rational design of self-powered polymer composite sensors in achieving human–machine interaction/interface are discussed.