Flexible piezoresistive three-dimensional force sensor based on interlocked structures

[Display omitted] •A novel flexible piezoresistive three-dimensional force sensor is developed based on interlocked structures.•Electrospray and laser direct writing technique is utilized for the fabrication of conductive polymer structures.•The sensors have a shear force direction resolution of below 30°, and is demonstrated for robotic grasping. Three-dimensional force sensing has attracted increasing attention due to the rising application requirements from smart robots. Herein, we report a flexible three-dimensional force sensor with an interlocked structure as bionic human skin, which consists of flexible silicone substrate and polymer composite materials. Surface piezoresistive layer is patterned through electrospray and laser direct writing. The sensing mechanism is based on the contact resistance changes from three interlocked hemispheres units from either the normal force or the shear force. Shear force directional detection is rendered through three-axis structural arrangement in-plane. As a result, the sensor displays a normal force sensitivity of 6.33 kPa−1, response time of 59 ms, and shear force angular resolution of below 30°. The manufacturing method is amenable for minimized sensor array fabrication. Further application is demonstrated with a mechanical arm for gripping objects, where the sensor provides in-time feedback for precise grasping.