CNTs-coated stretchable fabric as ultrasensitive e-skin for rotational motion monitoring in humanoid robots

Highly stretchable and sensitive strain sensors are immensely desired for motion detection in human-like robots. Here, we report an extremely facile fabrication of carbon nanotubes (CNTs) based ultrasensitive strain sensors. CNTs are coated on a flexible and stretchable commercial fabric using the spray-coating method. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirm that the CNTs are effectively embedded into fabric fiber frameworks where these act as conducting channels among the individual fibers. A strain sensor is fabricated using the CNTs coated fabric by simply stitching the copper wires along its two opposite edges. The strain is employed systematically and response of the sensor is recorded. The sensor shows an ultrasensitivity of 113,129% for an applied strain of 50% with a notable response and recovery time of 78 ms. The sensor also shows remarkable cycling stability for 5,000 stretching cycles. Moreover, the sensor is evaluated for rotational motion detection in robotics. The sensor with electrode length up to 10 cm can tolerate the rotational motion up to ~ 12,600° (~ 35 rotations), and delivers a stable response. The results show that the demonstrated sensor can act as e-skin for human-like robots where it can effectively monitor the robot motion particularly which involves large random and rotational movements.