Flexible Shear Sensor Based on Embedded Optoelectronic Components

Tactile shear stresses play an important role in the medical field and robotics. To monitor these stresses in situ, there is a need for unobtrusive flexible sensors that can be wrapped around curved surfaces or moving body parts. The presented sensor is based on changing coupling of optical power between a vertical-cavity surface-emitting laser (VCSEL) and a photodiode facing each other and separated by a deformable transducer layer. The required optoelectronic components were embedded in a polymer foil of only 40 μm thick, yielding a very thin and flexible total sensor stack of 250 μm thick. In the linear part of the range (between 2 and 5.5 N), the sensitivity of the prototype was -350 μA/N; the maximum measurable force was 5.5 N. However, by selecting the appropriate deformable sensor transducer material, the sensitivity and range can be tuned for a specific application.