On-chip MEMS tribometer devices until now have been much less sophisticated for dynamically sensing frictional forces than their FFM (friction force microscope) counterparts. In this article, we present a MEMS-based tribometer that can be used to measure dynamically, onchip and in-situ, the frictional properties of MEMS-scale contact geometries. The device provides the first FFM-like friction loops with contacting MEMS sidewall surfaces. Depending on the normal load two regimes of operation are identified. At low and intermediate loads, the frictional behaviour reflects wear-less relative motion of the silicon oxide surfaces of the MEMS device and we observe repeatable, irregular stick-slip behaviour, related to the surface roughness. At very high loads, wear causes changes in the topography of the contacting surfaces.