Integrable elastic fiber-optic tactile sensors for fingertip stress perception

Tactile sensors with high softness and multiplexing are highly desirable for applications in humanoid robotics and smart prosthetics. Current tactile sensors face bottlenecks in multi-channel dynamic sensing based on miniaturized and economical signal demodulation devices especially for manipulator grasping motion. Integrating tactile sensors into the manipulator fingertip and developing multi-channel chip scale optoelectronic demodulation device are promising to overcome previous limitations. Here, an integrable elastic fiber-optic tactile (IEFT) sensor enabled by a fiber-optic Sagnac interferometer is reported. The tactile sensor is fabricated by encapsulating a macro-bending fiber-optic Sagnac interferometer in an elastomeric silicone fingertip structure. The finger body is made of photosensitive resin, which fits perfectly with the fingers of a mechanical hand. Through optoelectronic signal demodulation integration, the tactile sensors array is able to distinguish different finger actions such as pressing, sliding, pinching, and gripping motion. Five-channel finger tactile sensors show an excellent stress sensing detection limit of 0.05 N and a response time less than 300 ms. Such tactile sensing system achieves miniaturized, economical dynamic measurement. The developed sensors array may pave the way for perception of surface shape and hardness, as well as robot hand motion recognition.