The liquid/liquid-waveguide-based absorption sensor

A light absorption sensor is based on phenomena of light absorption between in two flow stream layers with different refractive index in liquid/liquid (L2) waveguide in this letter. The diffusion between the core and the cladding forms the tapered L2 waveguide sensor. The taper can be controlled by the flow rates of the core and the cladding layers. The absorption sensor is fabricated using PDMS onto a microfluidic chip, which chip size is 3.5cm 3cm and the absorption length is 2cm. Two different aqueous dye solutions such as rhodamin 6G and methylene blue are measured and approved by the experimental results of the absorption sensor. The limitation of detection is 0.5ng/mL for rhodamin 6G and 0.16ng/mL for methylene blue. The L2 waveguide absorption sensor has high potential usage for the biological, chemical and medical measurement applications.