In a first aspect, a micro-fluidic device is presented, comprising: a micro-fluidic channel having an inner surface; a sensing region inside the micro-fluidic channel configured for adsorbing at least one analyte, the sensing region comprising a plurality of pillars positioned along the length of the inner surface of the micro-fluidic channel wherein the plurality of pillars are configured for creating an electromagnetic field localization thereby making the sensing region suitable for sensing plasmonic or surface enhanced Raman signals when irradiated; characterized in that: the plurality of pillars are further configured for creating a capillary action in the micro-fluidic channel when a fluid sample is present in the micro-fluidic channel. In a second aspect, a multiplexed plasmonic microchip for detecting at least one analyte in a fluid sample is presented, comprising: a plurality of micro-fluidic devices as presented in the first aspect; a supply system for providing the fluid sample to the plurality of micro-fluidic devices. Further, a method for detecting analytes is presented using a device according the first or second aspect.