New Interfaces to Silicon Photonic Microring Resonator Arrays for Chemical Separations

Abstract

Chemical separations typically rely upon unique chemical properties of target molecules for discrete identification. Universal detectors are an appealing alternative to detection methods like optical absorbance and fluorescence because they enable detection of analytes without these chemical signatures and can be performed without analyte modification (e.g. adding fluorescent tags). Silicon photonic microring resonator arrays are one such universal detector that facilitates chemical measurements using a refractive index-based (RI) approach. Currently, there is no commercially available refractive index detector for capillary electrophoresis. The work presented here strives to demonstrate the suitability of microring resonator arrays as a detector for chemical separations. Chapter one of this document presents an overview of existing technologies that incorporate universal analyte detection with chemical separations. Approaches for post-column and on-column detection of analytical separations are discussed and give a glimpse at ways that may be applied for future detector development. In chapter two, a novel approach for hyphenating silicon photonic microring resonator arrays with capillary zone electrophoresis (CZE) is discussed. A post-column detection interface enables universal analyte detection for different classes of molecules. Ultimately, this approach reveals a promising universal detection platform for capillary. Chapter three details the use of microring resonator arrays that have been functionalized with antibody-based capture reagents to perform multiplexed immunosampling of analytes separated by size-exclusion chromatography. Microring resonators have been shown in numerous applications to be a suitable detector for HPLC, but the use of modified sensors in series with chemical separations has not yet been demonstrated In this work, antibodies are separated and detected using multiplexed antibody capture agents. With the goal of a facile approach to interfacing a voltage-driven separation with the microring resonator platform, chapter four details a 3D-printed device that interfaces in a straightforward manner with microring resonator sensor chips. Voltage-driven analyte migration is integrated with multiplexed immunocapture in the form of nucleic acid oligomers, and compatibility with complex matrices is tested. Devices were printed from a wide variety of polymer resins via several different commercial printing strategies. In chapter five, a multilayer polydimethylsiloxane (PDMS) microchip device was developed to integrate electrophoresis with a microring resonator chip. A novel fabrication approach is described that yields a traditional t-channel device with an integrated gasket layer for incorporation with a microring resonator array chip. In chapter six, optimization of the microring resonator flow cell is discussed largely in the context of integrating a wall-jet flow effect for increasing the bulk sensitivity of microring resonators for high molecular weight polymers separated by gel permeation chromatography (GPC). Wall-jet fluidics are commonly used to increase mass transfer of molecules for surface-sensitive detection schemes and was implemented to circumvent this sensitivity decay. Chapter seven summarizes the progress within this document, namely integration of microring resonator arrays with separations for both bulk refractive index measurements and multiplexed biomolecular sensing. A series of suggested critical work is described for microring resonators that may also be applicable to other universal detection schemes. Work presented herein details bulk RI detection of carbohydrates and polyphosphates. Finally, leveraging the ability to functionalize microring resonators through multiplexed lectins has the opportunity to add a valuable dimension of chemical affinity information that is complementary to detectors like mass spectrometry.