Sandwiched microfluidic chip-based interferometric refractometer

We propose and experimentally show that a highly-sensitive optofluidics-based refractometer structure can be simply realized. Our key idea is based on the use of a very simple microfluidic chip structure that consists of only one flow channel. Specifically, we sandwich the two microfluidic chips in such a way that their flow channels are laterally shifted at a desired distance, forming two channels for use in our Young interferometric-based refractometer structure. Experimental demonstration using two large 1-mm-deep single-flow-channel microfluidic chips, a 635-nm wavelength laser diode, and a 1600×1200-pixel image sensor shows a measured very-high sensitivity of 5.62×10^-6 RIU/pixel with a measured resolution of 9.23×10^-7 RIU.