Improving the Mechanical Properties of Molecularly Imprinted Polymers for Selective Sensing of PFAS

Abstract

Current laboratory-based analytical techniques offer the gold standard for sensitivity and selectivity towards quantifying harmful pollutants in our environment. However, they require centralized facilities, highly skilled personnel, and are generally cost-prohibitive. Therefore, identifying novel and cost-effective solutions are needed to address these limitations while retaining robust sensing performance and measurement reliability. Combining soft materials science with engineering principles can be leveraged for the development of innovative sensing solutions for these environmental toxins.This thesis describes our progress on the development of robust, reliable, and decentralized sensing platforms for detection of environmental contaminants. Specifically, we focus on leveraging biomimetic properties of molecularly imprinted polymers (MIPs) as recognition elements for detection of per-and polyfluoroalkyl substances (PFAS), otherwise known as “forever chemicals.” We identify design principles for the fabrication of synthetic MIPs to improve the mechanical robustness and sensing performance for selective sensing of PFAS. Herein, Chapter 1 describes the design, fundamental principles, and application of MIPs as chemical sensors. Chapter 2 and Appendix A provide information on the effects of MIP fabrication parameters for tuning the mechanical properties and MIP sensor reusability. We demonstrate increasing the synthesis scan rate during the electropolymerization improves the MIP’s elastic recovery and sensing reversibility. The application from this chapter is fundamental insights on how to leverage the MIP fabrication parameters for development of practical and robust sensors. Chapter 3 and Appendix B leverage principles of transport phenomena to develop design rules for templating certain PFAS within MIP films. Furthermore, this work demonstrates the use of electroanalytical and spectroscopic techniques for quantitative imprinting characterization of nano-scale MIP films. Lastly, this work develops a comparative simulation from first principles to describe the highly complex electrosynthesis MIP process. Chapter 4 and Appendix C describe the translational research from laboratory-grade materials to portable platforms for electrochemical sensing of PFAS in real-world matrices. We demonstrate the MIP technology can be successfully transferred to portable, carbon-based screen-printed electrodes and further discuss certain limitations with the use of an indirect sensing strategy. Chapter 5 and Appendix D demonstrate the detection of PFAS by leveraging differential behaviors of complex emulsion emissive sensing particles. We demonstrate change in interfacial tension due to PFAS surfactant properties produce distinct effects on the morphological and optical emissions of biphasic oil-in-water droplets. Leveraging this phenomenon, we show complex droplets can detect a range of PFAS by tuning the surrounding surfactant environment. Our ultimate goal from this work is to engineer soft materials (i.e., MIPs and complex emulsions) with tunable interactions for the development of reliable, low-cost, and portable sensing platforms for PFAS detection.