Inverse Opal Sensors for Classification of Complex Mixtures

Abstract

Inverse opal-based photonic crystals have received considerable interest in recent years as colorimetric detectors for a range of applications, from point-of-care diagnostics to environmental sensing. In one particular incarnation, the W-Ink sensor technology developed in our lab extracts information about the properties or identity of a liquid from the wetting of inverse opal sensors with chemically modified surfaces. Although W-Ink’s utility has been demonstrated in proof-of-principle experiments such as those based on distinguishing between common laboratory solvents, its versatility has been as of yet untested in more nuanced scenarios, such as those involving comparisons between mixtures, particularly ones whose compositions vary in subtle and unknown ways. This thesis explores those next-level extensions of the W-Ink sensor technology, delving into applications involving complex mixtures and testing the boundaries of W-Ink’s resolution. It also seeks to understand and improve upon these resolution limits by examining the surface silanization process in-depth, teasing out the roles of various steps in the process in producing robust and reproducible sensor surface coatings. Chapter 1 introduces the foundations of the W-Ink technology, including an analysis of what is currently understood about its sensitivity limits and what knowledge gaps exist. Chapter 2 investigates the use of W-Ink sensors for classification of crude oil batches based on their volatility, with implications for safer rail-based transport of crude. Chapter 3 introduces new W-Ink silane chemistries to expand its capabilities from organic to aqueous mixtures, and then explores biomedical diagnostic applications related to the detection of bile salts in urine. Finally, Chapter 4 answers questions about the origins of variance in the W-Ink system primarily related to silane coatings, demonstrating that small differences in silane chemistries can have big implications for the reproducibility of the W-Ink wetting response from sensor to sensor.