On-chip refractive index sensors for lab-on-a-chip applications

Abstract

Optical waveguide-based refractive index sensing is an emerging technology for the sensitive monitoring of molecular interactions. This technology could fulfill the requirements for “on-chip” detection in lab-on-a-chip platforms due to their outstanding characteristics of high sensitivity, label-free, and real-time detection. Due to their compact and portable design, these optical sensors have the potential to become an essential tool in the field of biosensing, offering an efficient and reliable method for real-time diagnosis. This could provide significant advantages over current analytical methods. The focus of this thesis is to design and fabricate a novel optical waveguidebased label-free refractive index sensor. The aim is to develop a refractive index sensor with high sensitivity, a large measurement range, and the ability to multiplex. At the current stage, optical waveguide-based refractive index sensors are not used widely for commercial applications. This can be attributed to the challenges of the current waveguide-based sensor technology. For a sensor to become widely used for commercial application, it must possess high sensitivity, selectivity, wide measurement range, and multiplexing capability. The latter two features help reduce ambiguity in measurements, minimize the required sample volume, and improve the throughput to reduce the cost of sensor chips. This work has therefore concentrated on the development of a sensor system with all these features. This thesis presents contributions to developing a novel on-chip sensor and its integration with other components for a lab-on-a-chip sensing platform. The included papers document the proof of concept, fabrication, and characterization of the developedMach-Zehnder interferometer-assisted ring resonator configuration sensor. A paper on the development of bio-compatible microfluidics components for a lab-on-a-chip platform is also documented in the thesis. Additional investigation on an all-optical phase-modulatedMach-Zehnder interferometer sensor was done during the early part of the thesis and documented in the thesis.