An optofluidic Young interferometer sensor for real-time imaging of refractive index in μTAS applications

Abstract

This report describes a Young interferometer (YI) sensor for real-time imaging of refractive index (RI) along the length of microchannels. The YI comprised a unique combination of Fresnel biprism and cylindrical lens to obtain two wedge shaped light beams, which ultimately overlapped to produce the interference fringes. The measured temporal and spatial resolution of the reported YI is 2 s and 295 μm respectively. The RI resolution per mm of the optical pathlength of the YI sensor is 2.04 × 10−6 while providing information on spatial RI distribution in real-time. The ability of the reported YI to image RI in real-time was used to monitor electrokinetic transport of a model protein, bovine serum albumin (BSA), in agarose filled channels of a microfluidic device. This method is particularly suitable to planar μTAS devices as it is free-space, senses through the entire depth of the channel and requires no coupling devices such as gratings or prisms.