High-sensitivity gas sensors measure the presence of trace gases. They have a wide range of applications. Finnish SME Gasera has recently developed a MEMS-based mechanism for detecting the pressure waves created in photo-acoustic cells. This innovation can be used to realize infrared gas sensors of extreme sensitivity. Instead of the usual microphone (membrane with capacitive readout) the Gasera cell contains a "free-standing" silicon cantilever. The mechanical movement of the free end of the cantilever is 100x larger than the centre of a fixed membrane. Furthermore, the movement of the cantilever is detected interferometrically not capacitively. The resulting improvement in sensitivity by these innovations is about three orders of magnitude over the prior art. Three international patent applications are pending. Whereas other optical gas detection methods can not be miniaturized because of the long optical pathlengths needed for high sensitivity, theoretical analyses predict that the cantilever PA cell can be miniaturized. The goal is to build and demonstrate a miniaturised sensor sub-system that achieves two or three orders of magnitude better sensitivity (on sub-ppm level!) than other optical measurement methods could achieve at similar package volume. A much lower cost and wider temperature range of operation are also predicted.Keywordsphoto-acoustic, gas detection; high sensitivity; cantilever interferometric readout