Simple microfluidic chip structure for an alignment-free Young interferometry-based refractometer
Abstract
We propose a two-flow-channel microfluidic chip for use in a Young interferometry-based refractometer structure. Specifically, this work embeds the optical mask inside the microfluidic chip, thus completely eliminating precise free-space optical alignment between the optical mask and the microfluidic chip. The key idea is accomplished by permanently making the area surrounding the two flow channels opaque. Once the incoming optical beam passes through the two flow channels, it is automatically divided into two optical beams that will interfere with each other at the two-dimensional detection plane. Experimental proof of concept via a laboratory prototype having a two-flow-channel microfluidic chip with a channel spacing and depth ratio of 3, a 635 nm wavelength laser diode, and a 1600 × 1200-pixel image sensor shows a measured 4.28 × 10−5 RIU per pixel sensitivity with a measured resolution of 8.11 × 10−6 RIU. Other key features include simplicity, ease of implementation, and disposability.