In this communication, the design and the fabrication of a silicon‐glass microsystem for lab‐on‐chip sensing applications have been reported. Each component has been realised using wet etch process and the porous silicon (PSi) technology, while the final device has been obtained intimately joining all elements by the Anodic Bonding (AB) process. The flow injection analysis (FIA) principle has been adopted in the microfluidic manipulation of the analyte samples: very small volume of the substances can be quickly and repeatedly monitored. The transducer element of the sensor device is a PSi Fabry–Perot monolayer which allows a very effective interaction with several chemicals and biological molecules. Time resolved measurements revealed very rapid response times in detecting some volatile substances. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)