FOCWS: A High Sensitive Flexible Optical Curvature Sensor Inspired by Arthropod Sensory Systems

Flexible sensors for joint angle measurement play a crucial role in various human-robot interaction applications. In previous studies, sensors with various sensing mechanisms have been developed. Among them, optical waveguide sensors exhibit high resistance to environmental factors (such as temperature and humidity) and low sensitivity to electromagnetic interference. Researchers have enhanced the sensitivity of optical waveguide sensors to tensile strain by doping other substances (such as graphite) into the optical core material of the optical waveguide. However, the sensitivity of measuring joint angles based on tensile strain principles remains relatively low. In nature, arthropods utilize crack-like structures near their leg joints to perceive minute mechanical stress changes. Here, we propose a curvature sensor based on a Flexible Optical Crack Waveguide Structure (FOCWS) inspired by the arthropod sensory systems. By cutting the optical core, we increase its light power loss during bending strain, thereby enhancing the sensor’s sensitivity to angle measurement. The characteristics of light propagation and geometric parameters were studied through simulation, and experiments were designed to validate the simulation results. The average sensitivity is 0.068 dB/<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup>, which is nearly 300 times higher compared to uncut optical waveguide.