An FBG-Based Flexible Force Sensor for Stable Grasping in a Grow-and-Twine Gripping System

Soft robotic grippers are highly suitable for delicate object manipulation; however, the absence of integrated force sensors reduces precision and increases the risk of slippage. To address this challenge, we introduce a compact and flexible Fiber Bragg Grating (FBG)-based force sensor for accurate contact force measurement. The sensor features a 3D-printed Thermoplastic Polyurethane (TPU) casing with a localized bump to concentrate contact force and a uvula-inspired structure for highly sensitive lateral force sensing. It exhibits good repeatability with low hysteresis over 100 loading–unloading cycles, high force sensitivity (~913.5 pm/N), and effective temperature compensation. When integrated with a grow-and-twine gripper, the sensor demonstrated improved grasp stability and feedback control during pick-and-place tasks with various objects. The sensor can be deployed in manufacturing, agriculture, and healthcare (like prosthetic hands) where precise force measurement and operational efficiency are crucial.