Figure 2. A sensitive, real-time microfluid refractive index measuring system.

(a) A schematic illustration of the measuring system. The enlarged diagram shows the sandwiched structure of the GRIS. PBS separated the circularly polarized light into s- and p-polarized lights. (b) A schematic illustration of the GRIS. The light source can be a laser of any wavelength or even natural light. The absorption of s-polarized light is much greater than that of p-polarized light when fluid is flowing. (c and d) The real-time voltage signal change of microfluid with and without graphene when injecting N,N-dimethyl acetamide, deionized water, air, ethanol, air, a solution of 10% NaCl, air and water successively at a flow rate of 10 μL/s.