MEMS 6-axis force sensor chip for spike pins in athletic sports shoes

This study reports a microelectromechanical system (MEMS) sensor for evaluating the force acting on the spike pins of athletic sports shoes. The ground reaction force (GRF) of the human sole is a crucial factor in understanding running mechanics. In short-distance sprints, running is achieved by biting the ground using shoe spikes. However, it is difficult to evaluate the forces acting on such spike pins because of their small size. In this study, a MEMS sensor chip that could measure the 6-axis forces was embedded in an actual spike-pin-shaped structure, and the fabricated spike pin was attached to athletic shoes. By utilizing four pairs of surface- and sidewall-doped beams as sensing elements, the 6-axis force acting on the pin can be measured regardless of the force distribution when the pin bites into the track. We demonstrated that the force distribution could be measured using three sensors developed during running. The vertical force on each pin exceeded 100 N. Furthermore, it was observed that higher propulsive forces were exerted on all the spike pins in the first step compared to the second step or later steps. Therefore, the proposed method can be used to evaluate running mechanics using spike pins in athletic sports shoes.