The disclosed invention provides a fluid sensing device capable of collecting a biofluid sample, such as interstitial fluid, blood, sweat, or saliva, concentrating the sample with respect to a target analyte, and measuring the target analyte in the concentrated sample. Embodiments of the invention can also determine the change in molarity of the fluid sample with respect to the target analyte, as the sample is concentrated by the device. Some embodiments of the disclosed invention provide a fluid sensing device comprising minimally invasive, microneedle-enabled extraction of interstitial fluid or other biofluid for continuous or prolonged on-body monitoring of biomarkers. Some embodiments allow the collection and measurement of analytes in of non-biological fluids, such as fuels, or bodies of water.
