Shape-sensing sheet digitally tracks its own movement as it bends and twists

Researchers at MIT developed a flexible, stretchable shape-sensing sheet that digitally reconstructs its 3D form as it bends and twists. Rather than using rigid, stitched sensors, the design embeds multiple soft optical waveguides - clear rubber cores with dyed rubber cladding - throughout a silicone sheet in a zig-zag pattern. Each fiber is intentionally roughened on one side so bending toward the rough or smooth face produces distinct light-scattering signatures. LEDs inject light and photodetectors read outputs; an algorithm converts the per-fiber light changes into local curvature estimates and fuses them into a near-real-time surface reconstruction.

Simulations identified the optimal fiber layout; physical prototypes tracked folding and twisting motions smoothly and tolerated partial fiber cuts without losing overall accuracy. Quantitative tests using 3D-printed molds yielded reconstruction errors under 0.4 cm, versus typical 1-2 cm errors for rigid-sensor systems. Current fibers are about 1 mm thick but fabrication methods can shrink them to tens of micrometers to allow denser arrays and finer detail. Practical applications span wearable motion capture for virtual reality and gaming, teleoperation, and objective, continuous tracking of patient range of motion in physical therapy.