Nanophotonic Technologies For Manipulating Biomolecules And Investigating Molecular Interactions

Abstract

This dissertation aims to develop nanophotonic technologies by integrating photonic-crystal-based nanostructures with microfluidic techniques. Firstly, a selfassembled photonic nanostructure is developed to exploit that a range of colors on incident light will reflect on a crystalline structure with appropriate periodicity. The photonic crystal substrates are utilized to demonstrate a technique for creating erasable, high-resolution color images with transparent inks. The photonic-crystal-based technique is applied to construct a photonic crystal resonator in the waveguide through which light travels and is confined in small mode volume. The confined light energy enables the optical force experienced by a trapped dielectric nanoparticle. Based on this principle, angular orientation and rotational control of both biological and non-biological nanoscale rods are demonstrated using a photonic crystal nanotweezer to extend the capabilities of near-field optical techniques, including trapping, transport, and handling of nanomaterials. In experiments, single microtubules (diameter 25 nm, length 8 [mu]m) and multi-walled carbon nanotubes (outer diameter 110 - 170 nm, length 5 [mu]m) are rotated by the optical torque resulting from their interaction with the evanescent field emanating from these devices. An angular trap stiffness of k = 92.8 pN[MIDDLE DOT] nm/rad2-mW is demonstrated for the microtubules and a torsional spring constant of 22.8 pN nm/rad2-mW is measured for the nanotubes. Finally, the near-field optical technique is utilized to develop a label-free method for measuring the binding affinity and stoichiometry of free-solution interactions between antibodies and single influenza viruses at the attogram scale. Common approaches, including optical, electrochemical, and mechanical detection schemes require immobilizing one or both of the interacting molecules on an assay plate or a sensor surface, which constrains their active binding. This restriction prevents a precise measurement of their affinity and binding capacity, especially when one of the interacting biomolecules is much larger than the other and multivalent, for example a virus and an antibody. The method, however, presented here detects specific binding by analyzing changes in the confined Brownian motion of the virus, which is trapped but not immobilized using a photonic crystal resonator.