Flexible optical smart skin with high-density tactile sensing nodes using a single strand of optical fiber via distributed polarization analysis

• We introduce a novel optical smart skin that features a dense array of tactile sensing nodes (up to 100 per cm 2 ) using a single strand of single mode optical fiber sandwiched between a 2D array of touching pads and a flexible substrate. • The optical smart skin demonstrates an excellent linear response, with a high sensitivity enabling the detection of pressing forces below 10 −3 N and a spatial resolution on the order of millimeters. • A key advantage of the optical smart skin is that its data processing time and energy consumption remain constant regardless of the number of sensing nodes, enabling its use in high density tactile sensing applications. The tactile information is critical for enhancing robot intelligence and human-robot interactions. Here, a novel optical smart skin (o-skin) featuring a dense array of tactile sensing nodes (up to 100 per cm²) using a single strand of single-mode optical fiber between a 2D array of touching pads and a flexible substrate is introduced. This design addresses the prevalent challenges of electronic tactile sensor arrays, such as intricate wiring layouts, high energy consumption, inter-sensor crosstalk, and susceptibility to electromagnetic interference. Our sensor array leverages full Mueller matrix distributed polarization analysis to decode distance-resolved birefringence data along the optical fiber, translating it into precise force information at each tactile node. Experimental validation demonstrates the sensor's excellent linear response and high sensitivity to external pressing force, with spatial resolution optimized to the millimeter scale. Notably, the system's data processing time and energy consumption is independent of the number of sensing nodes, making it attractive for high-density tactile sensing applications. Beyond tactile sensing, the same system can be extended to simultaneously sense temperature and strain, paving the way for multi-functional smart skin. Our work points to a new direction for smart skin research and will prove fruitful for diverse applications involving tactile sensing.