Polymer Brush-Modified Microring Resonators for Partition-Enhanced Small Molecule Chemical Detection

Silicon photonic microring resonators have emerged as a promising technology for the sensitive detection of biological macromolecules, including proteins and nucleic acids. However, not all species of interest are large biologics that can be targeted by highly specific capture agents. For smaller organic chemicals, including many toxic and regulated species, a general approach to improving sensitivity would be desirable. By functionalizing the surface of silicon photonic microring resonators with polymer brushes, small molecules can selectively partition into the surface-confined sensing region of the optical resonators. This in turn leads to response enhancements in excess of 1000% percent, relative to non-functionalized sensors, for representative targets including 4-methylumbelliferyl phosphate, a simulant for highly toxic organophosphates, Bisphenol A, an industrial pollutant, as well as other small organic analytes of interest. There are many polymer brush chemistries compatible with silicon resonators, making this a general strategy towards tuning sensor selectivity and specificity by optimizing interactions between the agent(s) of interest and the polymer construct.