Design and Application of Fully Flexible Capacitive Three-dimensional Force Sensor Based on Liquid Metal

Abstract Flexible three-dimensional (3D) force sensors have received extensive attention from researchers due to their characteristics of being able to detect both normal forces and tangential forces. However, most current flexible 3D force sensors still use metal electrodes, which have posed challenges such as low bending and stretching properties, easy fracture, and larger mass. Herein, this paper proposed a fully flexible 3D force sensor utilizing liquid metal directly as the electrode to achieve full flexibility. Besides, a dielectric layer with a porous pyramid array structure was adopted to improve the properties of the sensor. The influence of the square and triangular electrode shapes on the performance of sensor was verified through theoretical deductions and experiments. The results show that the triangular electrode sensor exhibits higher sensitivity. The maximum sensitivity of the triangular sensor in the normal +Z direction is , and the maximum sensitivities in the tangential +X and +Y directions are and , respectively. Moreover, the sensor possesses rapid response performance (143ms), low hysteresis (3.61%), high resolution, small temperature and humidity drift, satisfactory dynamic stability, and long-term stability. Finally, the sensor was installed on a manipulator for object grasping, verifying its ability to detect 3D forces and its potential in non-destructive grasping.