Sensor comprising mechanical amplification of surface stress sensitive cantilever

The invention relates to a sensor comprising one or more sensor units, wherein at least one of the sensor units is in the form of a poly-cantilever structure. The poly-cantilever structure comprise two or more cantilever-like structures, at least one of the cantilever-like structures comprises a piezoresistive element, and at least one of the cantilever-like structures comprises a capture surface, at least one cantilever-like structure with a piezoresistive element designated a piezoresistive cantilever being connected in an amplifying connection to at least one of the cantilever-like structure with a capture surface designated a capture surface cantilever. The amplifying connection being provided so that a deflection of said capture surface cantilever due to a stress generated at said capture surface being capable of deflecting the connected piezoresistive cantilever. The sensor can be used for detection of a target substance in a fluid, such as a gas or a liquid.