Fiber-Optic Optofluidic Platform for in-situ Process Monitoring of Layer-by-Layer Assembled Functional Polyelectrolyte Thin Films

Henry H. Du, Stevens Institute of Technology, DMR1206669

Fei Tian et al., Sens. Actuators B. 196, 475-479 (2014).

This project aims to design, fabricate, and demonstrate a novel optofluidic platform with highly index-sensitive long-period gratings as the enabler for in-situ monitoring of molecular layer-by-layer (LbL) assembly of functional polyelectrolyte thin films and their response to external stimuli with potential utility as sensors, actuators, and test beds for thin film design and evaluations. The effect of geometric confinement on the LbL assembly and responsiveness is being investigated.

Via simulation-guided design and fabrication, we have identified and implemented higher-order mode coupling (LP0,10 mode) in long-period gratings in conventional optical fiber with two orders of magnitude improvement in sensitivity compared to the commonly pursued grating structures that support only lower-order mode couplings (e.g., LP0,2, LP0,3, LP0,4). This progress has opened the door for us to realize simple, cost-effective, and robust optofluidic platform to study the kinetics and mechanisms of LbL assembly of polyelectrolyte films and their response to stimuli under a wide range of conditions. One example is the demonstrated utility of such a platform for real-time and in-situ monitoring of the construction of a drug-eluting polyelectrolyte film, [CHI/PAA/GS/PAA]n (top figure) and the subsequent release of the drug, GS (bottom figure).

Real-time, in-situ monitoring of drug release under dynamic conditions.

Dramatically enhanced sensitivity of higher order cladding mode LP0,10 in fiber gratings and its use for the monitoring of deposition of the drug-eluting [CHI/PAA/GS/PAA]n thin film.

We have established a strong and fruitful collaborative relationship with the Institute of Photonics and Electronics (IPE) in the Czech Republic. Dr. Jiri Kanka of IPE has been contributing his fiber optic numerical analysis expertise and training our students through regular communications and particularly via yearly visits with the PI. This collaboration has yielded greater insights into the fundamental details on mode coupling and mode distributions in fiber gratings and provided meaningful international exposure to our students.

Our work was highlighted at the Conference on Layer-by-Layer Assemblies: Science and Technology in June, 2014 at Stevens. This conference was inspired by numerous recent advances in the field, including our project findings and was co-chaired by the Co-PI and Prof. Michael Rubner of MIT. It attracted an international audience. Our research also promoted a lot of interesting discussions with the conference attendees, setting a stage for potential future collaborations.

Expanding International and Domestic OutreachHenry H. Du, Stevens Institute of Technology, DMR1206669

• NSF WORKSHOP ON US-CZECH FRONTIERS IN PHOTONICS

PRAGUE, THE CZECH REPUBLICAPRIL 18-19, 2013Sponsored by ECCS and OISE of NSF and in Partnership with IPE, ASCR 

                      ©2013 Stevens Institute of Technology. All rights reserved. Castle Point on Hudson, Hoboken NJ 07030-5991

(Top) The Du group with Dr. Jiri Kanka (left most) of the Institute of Photonics and Electronics, the Academy of Sciences of the Czech Republic. (Bottom) Flyer of the Layer-by-Layer Assemblies: Science and Technology Conference.