Coil-shaped multimode polymer optical fibers for robotic tactile perception

Optical fiber tactile sensors capable of measuring contact forces are emerging as potential components for intelligent robotics. The demand for innovative fiber sensor designs and effective fabrication techniques to enhance tactile sensing performance is growing. In this study, we propose and demonstrate a robotic tactile sensor utilizing the coiled multimode polymer optical fiber (POF). The fiber coils are formed by winding commercial polymethyl methacrylate (PMMA) optical fibers around a steel needle and applying heat to maintain the coil configuration. The polymer fiber coil is then integrated into polydimethylsiloxane (PDMS) substrates for mechanical support and protection. Under external pressure, the fiber coil deforms, leading to a reduced bending radius and an increase in bending loss. Experimental results show that sensitivity and dynamic range can be adjusted by varying the number of coils. A resolution of 0.024 N and a dynamic range of 0-10 N for the detection of normal force were achieved with a coiled POF featuring a coil diameter of 1.125 mm and a coil quantity of 8.5. Ultimately, we integrated a coiled fiber tactile sensor array onto the finger of a robot manipulator to enhance grasping capabilities, demonstrating its potential for practical applications. The proposed coiled fiber sensor may potentially inspire new sensing devices and find use in smart homes and healthcare.