MedE Ph.D. Defense: Haeri Park Hanania
Nanophotonic application to biomedical devices
Nanophotonics is the study of interactions between light and nanoscale structures. It has been applied in various fields over the past few decades, taking advantage of advances in NEMS/MEMS technology. When a nanophotonic structure consists of metals, it is considered a plasmonic structure, which holds its own category due to the unique properties of metals forming plasmons – a collective motion of electrons in the conduction band of metals – and therefore enabling confinement of electromagnetic energy at the metal-dielectric interface. Due to its ability to enable the confinement of electromagnetic energy within nanoscale volumes, plasmonics has been successfully applied to many fields, including photovoltaics, spectroscopy, and biomedical devices.
This presentation provides 2 major applications of nanophotonics, and particularly plasmonics, to the improvement of biomedical devices. First, I will discuss the application of nanophotonics to targeted molecular sensing. An open-top, tapered waveguide that serves as a 3-dimensional plasmon cavity is shown to overcome the evanescent field decay that is inherent to most plasmonic devices and inhibits reliable sensing of various sized molecules. With the optimized design that combines the body, 3-dimensional taper, and tip, the 3-dimensional plasmon cavity achieves consistent performance for molecules of various sizes at a near or single molecular detection level. Next, I will discuss the application of nanophotonics to angle-and-polarization independent pressure and strain sensing. In the field of medicine, where objects are alive and moving, most plasmonic devices lack practicality due to the angle and polarization sensitive nature of plasmons, which require precise alignment or a trained technician. Inspired by the geometry and optical principles of butterfly corneas, an array of gold paraboloids introduced with a plasmonic refractive index gradient is designed to support a surface plasmon resonance that is angle-and-polarization independent. When integrated onto a flexible membrane of a hermetically sealed cavity, the plasmonic refractive index gradient array enables angle-and-polarization independent pressure and strain sensing and achieves over an order of magnitude greater resolution over wide angle. Advisor: Mory Gharib