Three-dimensional skin-type triboelectric nanogenerator for detection of two-axis robotic-arm collision

Triboelectric nanogenerator (TENG)-based sensors afford the advantages of high sensitivity, high reaction speed, and self-powering capability. This study presents a flexible two-axis force triboelectric nanogenerator (TF-TENG) capable of collecting and sensing mechanical energy using a PolyJet 3D printer. The proposed TF-TENG comprises a mixture of the Agilus30 and digital acrylonitrile butadiene styrene (ABS) filament to produce a structure that can be easily compressed under the action of a small force. The positively charged material was prepared in the form of a cylinder using nitrile rubber and stainless steel (SS) ropes, while its negatively charged counterpart was prepared by mixing copper wool with silicone rubber. The proposed TF-TENG operates based on the contact-separation mode mechanism and obtains electrical output based on electrostatic induction and the triboelectric effect. In addition, when manufactured as a module that does not require a separate gap for the insertion of triboelectric cylinders into the 3-dimensional (3D) structure, the TF-TENG can be used in different applications without restrictions in terms of space or location. Because the triboelectric cylinders are cross-inserted in cathode-anode pairs, two-axis sensing can be performed by determining the vertical and horizontal forces. The proposed TF-TENG achieved an output of 160 V and 5.5 μA at an operating pressure of 3.5 kPa. In addition, an emergency robot-arm stop system has been developed using an appropriate circuit. By attaching the TF-TENG as a skin to a robot arm, the skin can be utilized as a collision-detection sensor that stops motion upon collision with a worker or another object.