A sensor device (6) for use in a liquid medicament delivery system has a micro-fluidic chamber (1) comprising a rigid bottom substrate (11) and a cover (12), and an optical detection system (5) that is arranged to emit one or more light beams (53a) toward the cover membrane (12) and to observe the one or more light beams (53b) reflected from the cover membrane (12). The optical detection system (5) is arranged on a side of the bottom substrate (11) opposite to the cover membrane (12).
