Lab-in-a-Fiber Optofluidic Platform: In-Situ Assembly and Response of Layer-by-Layer Polyelectrolyte Films in Confined Geometry

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This project is jointly funded by the Electronic and Photonic Materials Program (EPM) in the Division of Materials Research (DMR) and the Electronics, Photonics, and Magnetic Devices Program (EPMD) in the Division of Electrical, Communications and Cyber Systems (ECCS).Technical Description: This project is a theoretical and experimental investigation to integrate layer-by-layer (LbL) assembly of functional polyelectrolyte thin films with a long-period grating structure inscribed in index-guided photonic crystal fiber. The integrated system represents a lab-in-a-fiber optofluidics platform by virtue of its high refractive index sensitivity and the feasibility for molecular/nanoscale functionalization in axially aligned cladding air channels. The research is designed to gain fundamental insights into distinct features of LbL growth in fiber and to probe the response of the LbL film to stimuli in confined geometry in order to demonstrate the feasibility of the integrated scheme for optofluidic sensors. Project activities entail (1) simulation of mode coupling in various lab-in-a-fiber configurations to determine optimal platform with the highest possible index sensitivity; (2) inscription of the grating structure with the simulation as a guide to realize mode coupling at prescribed resonant wavelengths; (3) deposition of LbL polyelectrolytes with different propensity to chain exchange with a multitude of parameters while measuring the shift in resonance wavelength in situ; and (4) evaluation of the pH response of polyacid-based hydrogels constructed via LbL in the lab-in-a-fiber platform. The central goals of this project are to (1) establish a novel lab-in-a-fiber optofluidics to study LbL deposition in situ; (2) provide important insights into the distinct features of LbL deposition and response in confined geometry; and (3) build a knowledge foundation for the exploration of lab-in-a-fiber optofluidic sensing.Non-technical Description: The research component of this project is to investigate layer-by-layer thin-film growth inside a special type of optical fiber, photonic crystal fiber with long-period grating structure, and to study the response of the thin film to stimuli in confined geometry. The success of the project is expected to bring to basic and applied research community and potentially the market place a transformative lab-in-a-fiber optofluidic stimuli-responsive platform for scientific exploration and technological applications. From educational perspective, this project engages doctoral students, undergraduate students, as well as high-school students. Dissemination of research results is achieved via various channels, including peer-reviewed publications, conference presentations, web posting, and case studies in classrooms.