Cornell researchers have created a fiber-optic sensor utilizing inexpensive LEDs and dyes that resulted in a stretchable skin-like material able to detect deformations, including pressure, bending, and straining. The sensor could have soft robotic systems applications and could be a game-changer for augmented reality technology. A soft wearable sensor could allow augmented reality users to feel sensations similar to those felt in the real world.
The technology has other applications as well, and the researchers are currently working to commercialize the technology for use in physical therapy and sports medicine. Their work builds on prior stretchable sensor work created in the lab of Rob Shepherd, who also led the team in the new research.
The earlier stretchable sensor was created in 2016 and used light sent through an optical waveguide and a photodiode to detect changes in the beam’s intensity to determine when the material deformed. For the new project, researcher Hedan Bai drew inspiration from silica-based distributed fiber-optic sensors able to detect minor wavelength shifts as a way to identify multiple properties, including changes in humidity, temperature, and strain.
Silica fibers are incompatible with soft and stretchable electronics. The solution was to make a stretchable light guide for multimodal sensing (SLIMS) sensor. That is a long tube that contains a pair of polyurethane elastomeric cores. One core is transparent, and the other is filled with absorbing dyes at multiple locations and connects to an LED. Each core is coupled with a red-green-blue sensor chip able to register geometric changes in the optical path of light.
Using a dual-core design increases the number of outputs the sensor can use to detect a range of deformations, including pressure, bending, or elongation. It indicates deformations by lighting up the dye, which acts as a spatial encoder. The tech is paired with a mathematical model able to decouple the different deformations and pinpoint their exact location and magnitude. A SLIM sensor can operate with small optoelectronics with lower resolution making it less expensive and easier to manufacture and integrate into systems. This sensor could be incorporated into a robot hand to detect slippage or wearable gloves for VR/AR users.