A Soft Optical Waveguide Coupled With Fiber Optics for Dynamic Pressure and Strain Sensing

As the use of soft robotics and soft actuators becomes more popular, there is also an increased need for soft sensors that can perform robustly under various extreme conditions. While some applications find ultrathin flexible sensors sufficient, like electronic skin and wearable devices, there is still a critical need for robust sensing under extreme deformations. Previous work in highly stretchable sensing modalities commonly uses liquid conductors that couple a change in measured electrical resistance with applied stress. However, liquid conductors are expensive and difficult to encapsulate, leading to leakages that can damage machinery. As an alternative, this letter proposes an elastomeric waveguide coated with a thin reflective metallic layer that reflects internally propagating light. Upon deformation, microcracks in the reflective layer modulate the intensity of the light at the photodetector, leading to decrease in optical power. This letter describes the design, fabrication, and characterization of the proposed optical soft sensor. A prototype was created and characterized for pressure and strain up to 110 kPa and 30% strain, respectively.