Measurement of the pressure distribution during the onset of slip

We report on the direct measurement of the pressure distribution of the contact surface between an elastic block and a rigid plate during the onset of slip. The measurement was carried out by using an array of seven MEMS pressure sensors embedded inside the elastic block. The results showed that the external loading force in lateral direction caused the inhomogeneous change in pressure along the contact surface: the pressure in area close to the trailing edge decreased while that at area close to the leading edge increased. This result explains why the local slip always started to occur from the trailing edge where the pressure became small.