A microfluidic device for detecting a characteristic of a fluid, the microfluidic device comprising a microfluidic channel having at least an inlet channel for receiving a fluid plug and preferably also an outlet channel for removing a fluid plug, the width W of the microfluidic channel being substantially larger than the width w of the inlet channel and preferably also the outlet channel, wherein the microfluidic device is adapted for detecting with at least one detector a physical or chemical property of the fluid, the microfluidic device being configured for detecting the property in a detection area positioned across the microfluidic channel in a width direction of the microfluidic channel, wherein the microfluidic device comprises a pillar based flow distributor for reorienting the fluid plug in such a way that the long axis of the fluid plug essentially is oriented perpendicular to the walls of the microfluidic channel being in the transverse orientation, as opposed to its original orientation, in which the longer axis is oriented in the longitudinal direction of the narrower inlet channel, and the microfluidic device is configured for having a detection area positioned within a distance D of an exit or an entrance of the pillar based flow distributor being smaller than the width W of the microfluidic channel, wherein the microfluidic device is configured for providing an interaction between the sample and a radiation beam for determining an optical property of the sample, and the microfluidic device comprises a collimating means and/or guiding means configured for limiting the radiation by confining the radiation to the detection area wherein the microfluidic device is configured for detecting the physical or chemical property by measuring in the width direction, in a transverse direction with respect to the average flow direction in the microfluidic channel. a microfluidic channel having at least an inlet channel for receiving a fluid plug and preferably also an outlet channel for removing a fluid plug, the width W of the microfluidic channel being substantially larger than the width w of the inlet channel and preferably also the outlet channel, wherein the microfluidic device is adapted for detecting with at least one detector a physical or chemical property of the fluid, the microfluidic device being configured for detecting the property in a detection area positioned across the microfluidic channel in a width direction of the microfluidic channel, wherein the microfluidic device comprises a pillar based flow distributor for reorienting the fluid plug in such a way that the long axis of the fluid plug essentially is oriented perpendicular to the walls of the microfluidic channel being in the transverse orientation, as opposed to its original orientation, in which the longer axis is oriented in the longitudinal direction of the narrower inlet channel, and the microfluidic device is configured for having a detection area positioned within a distance D of an exit or an entrance of the pillar based flow distributor being smaller than the width W of the microfluidic channel, wherein the microfluidic device is configured for providing an interaction between the sample and a radiation beam for determining an optical property of the sample, and the microfluidic device comprises a collimating means and/or guiding means configured for limiting the radiation by confining the radiation to the detection area wherein the microfluidic device is configured for detecting the physical or chemical property by measuring in the width direction, in a transverse direction with respect to the average flow direction in the microfluidic channel.