Optofluidic biosensor using integrated waveguide spectrometer

Project Summary Spectroscopic analysis based on a wavelength-dependent sample response is an invaluable and ubiquitous tool in diagnostics and fundamental biomedical research. It allows for multiplex analysis, either using continuous spectra (e.g. Raman spectroscopy) or using distinct and discrete labels. These principles are increasingly being implemented in compact lab-on-chip settings, including optofluidic devices in which optical and fluidic functions are integrated on the same chip. However, miniaturization of spectrometers has been a major challenge as conventional dispersion-based instruments scale poorly with size. Only recently, new approaches based on photonic elements and reconstruction algorithms have started to emerge, but they have not been used in conjunction with highly sensitive multiplex bioparticle detection. The goal of this project is to overcome this challenge by introducing and validating a new paradigm for multiplexed spectral bioparticle analysis on a chip. The specific objectives of this application are to incorporate a high-performance spectrometer on an optofluidic chip to enable spectral classification of fluorescence signals from single biological nanoparticles. Our central hypothesis is that this can be accomplished by leveraging emerging photonic design methodologies to build a multi-mode waveguide whose light propagation patterns can be imaged from the top. The addition of a nanostructured metasurface will allow for guiding specific wavelengths to spatially well separated spots for easy observation with a camera. The objectives of this application will be accomplished by the following Specific Aims: (1) Demonstration of detection of individual nanoparticles on integrated MMI waveguide spectrometer that is optimized by end-to-end photonic design; (2) Design and demonstration of a nanopatterned metasurface for spectral particle classification; and (3) Multiplex direct detection of individual exosomes from cerebral organoid cultures. The main innovative contributions of the proposed work are: (i) a novel waveguide-based spectrometer that can be seamlessly integrated on a fluidic chip; (ii) end-to-end inverse photonic design of a nanostructured metasurface for efficient and easy classification of different wavelengths; and (iii) validation of the novel device with a multiplex fluorescence assay of individual exosomes. The proposed work is significant because it will introduce the first high- performance integrated spectrometer for both discrete and continuous spectral analysis in a lab- on-chip format. Thus, this approach is suitable for both fundamental research and numerous applications, such as Raman and fluorescence spectroscopy.