Fabrication of a Shear Stress Sensor Matrix Using Standard Printed Circuit Board and Overmoulding Technologies

In contrast to pressure distributions that can, nowadays, easily be measured using commercial sensor sheets, this is not yet the case for frictional or shear stresses. Those stresses act parallel to a surface, which makes it more challenging to develop suitable sensors. A number of shear sensor prototypes have been reported until now, but realizing a matrix of shear sensors remains a big challenge because of cost and complexity issues. Therefore, this article presents a fabrication approach for realizing a matrix of shear sensors using standard PCB and molding technologies. The presented sensor is based on changing the coupling of optical power between a light-emitting diode and a set of photodiodes in combination with an overmolding step, as realizing a mechanical transducer. To demonstrate the fabrication flow, a first demonstrator incorporating a five-taxel sensor matrix has been realized, which is able to record the in-plane shear stress magnitude and direction.