Ultra Thin Optical Tactile Shear Sensor

Abstract

Tactile shear sensors gain importance for example in the field of robotics and biomedical sciences. For these applications, an "artificial skin"-like solution is needed with very thin and flexible unobtrusive sensors that can be wrapped around irregular surfaces or body parts. We present a tactile shear sensor based on the changing optical coupling between a light source (Vertical-Cavity Surface-Emitting Laser (VCSEL)) and a photodiode, separated by a transparent deformable transducer layer. When shear stress is applied onto the stack, both components move laterally and the photodiode captures a differing amount of light. Commercially available bare die VCSELs and photodiodes were thinned down to 20colonm and then packaged in flexible polyimide foils (40colonm thick) to allow fabricating this flexible and thin sensor. The use of spin-coatable polyimide resulted in low-stress packages for these optoelectronics.