IDBR: A label-free biomolecular sensing instrument based on monolithic optical resonators and an optoelectronic swept-frequency semiconductor laser

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Project Abstract This project proposes the development and demonstration of a label-free sensing instrument based on the integration of an electronically controlled linear swept-frequency semiconductor laser, a high quality factor (Q) optical resonator with covalent surface functionalization, and a microfluidic cell for analyte delivery. It will address a number of key issues that currently prevent this technology from becoming an accessible, affordable, and useful tool. These efforts will develop the optical cavity sensing platform to a point where it is robust and repeatable, and provides sensitivity and cost-effectiveness that are at least an order of magnitude better than any available alternative biomolecular assay instrument. The proposed system will combine the results of two major recent developments in the field of optical and laser physics: the high-Q optical resonator and the phase-locked electronically controlled swept-frequency semiconductor laser. The high-Q optical resonator is part of a monolithic unit with an integrated optical waveguide, and is fabricated using standard semiconductor lithography-based methods. Optoelectronic swept frequency lasers will be developed at wavelengths relevant for aqueous sensing, and will replace expensive and fragile mechanically-tuned laser sources whose frequency sweeps have limited speed, accuracy and reliability. The resonator will be functionalized using known techniques providing an adaptable and selective surface chemistry. The sensor will include an integrated microfluidic flow cell for precise and low volume delivery of analytes to the resonator surface. The proposed instrument represents an adaptable and cost-effective platform capable of various sensitive, label-free measurements relevant to the study of biophysics, biomolecular interactions, cell signaling, and a wide range of other life science fields. It will be capable of binding assays, thermodynamic and kinetics measurements, and has the potential for additional impact through integration into existing instruments to replace less sensitive analytical methods. The sensor also has potential applications in point-of-care medical diagnostics, where it can enable early detection of relevant antigens. The project is inherently multidisciplinary and will develop expertise in and better understanding of the interplay between such diverse fields as semiconductor lasers, optical nanofabrication, high speed electronics, control systems, fiber-optics, microfluidics, biomolecular binding assays, mass transfer, and integrated instrument design. It affords the opportunity for two graduate students and an undergraduate student to take part in a collaborative research effort under the close guidance of the PIs, educating the students in the culture of scientific discovery, alongside engineering and application considerations. The results obtained during the course of the project will be published in leading scientific journals and conferences.