Patent ID: 8254733

Claim:
A sensor comprising: a substrate comprising a flow channel for conveying a fluid, wherein the flow channel comprises a first region and a second region that are separated by a first distance, and wherein the flow channel is dimensioned and arranged to enable flow of the fluid from the second region to the first region; the second region, the second region being dimensioned and arranged to enable injection of a sample containing a first analyte into the fluid at the second region; a first optically resonant element that is located within the first region, wherein the first optically resonant element is optically resonant for a first spectral component when the fluid in the first region has a first refractive index, and wherein the first optically resonant element is optically resonant for a second spectral component when the fluid in the first region has a second refractive index; and a processor, the processor operable to (1) induce injection of the sample into the fluid at a first time, (2) detect a change in the resonance of the first optically resonant element at a second time, and (3) compute a time differential between the first time and the second time; wherein the refractive index of the fluid is based on the presence of the first analyte.