Triboelectric nanogenerators enabled sensing and actuation for robotics

Sensing and actuation systems that are capable of sensing various external stimuli and interacting with outside world are considered to be essential components for intelligent robots. The recent rise of soft robotics has inspired extensive enthusiasm in the development of flexible and soft sensors and actuators. Triboelectric nanogenerators (TENGs), which have been presented as promising power sources to drive actuators and function as self-powered sensors, provide a unique approach for the development of flexible and soft sensors and actuators for robotics. In this review, TENG-enabled flexible sensors and soft actuators, potentially for applications in robotics, especially soft robotics, are presented. We present the theoretical analysis on TENG-based pressure sensors for thorough understanding and rational design to improve measurement sensitivity. Strategies of materials synthesis and device fabrication of TENG-based pressure sensors to achieve high performances in terms of sensitivity, spatial resolution, as well as device flexibility or stretchability, are highlighted as those features are critical metrics of flexible sensory devices. Furthermore, TENG-enabled sensors for displacement, acceleration, vibration, acoustic, and multimodal sensing are discussed in details, demonstrating the capabilities of TENG for multimode sensing. Actuation schemes based on TENGs, particularly those based on dielectric elastomer actuators, electrostatic forces and electroadhesion, are summarized as they can be adopted for locomotion, materials handling and manipulation in robotics. Opportunities and challenges for the applications of TENG-based sensing and actuation in robotics are also discussed.