PhD defence by Leonid Beliaev
Principal supervisor: Associate Professor Andrei Lavrinenko, DTU Electro, Denmark
Co-supervisor: Senior Researcher Peter E. Andersen, DTU Health Tech, Denmark
Co-supervisor: Senior Researcher Osamu Takayama, DTU Electro, Denmark
Professor Kresten Yvind, DTU Electro, Denmark
Professor Duncan Sutherland, Aarhus University, Denmark
Professor Martina Gerken, Christian-Albrechts-Universität zu Kiel, Germany
Master of the Ceremony:
Associate Professor Sanshui Xiao, DTU Electro, Denmark
Optical sensors are typically compact, fast, and precise tools capable of providing quantitative measurements for almost any kind of measurand. One of the most common optical sensing techniques uses the change in refractive index caused by the presence or binding of an analyte. Recently, optical biosensors using dielectric and metal gratings have attracted researchers’ attention. They exhibit a sharp and sensitive optical resonance and can serve as an excellent sensing platform.
This project aims to realize novel gratings structures for biosensing applications. Two types of systems were studied: silicon and titanium nitride based structures. Silicon samples were one-dimension (1D) so-called high-contrast gratings (HCG) (conventional, pedestal, and half-buried designs), as well as two-dimension (2D) gratings that consist of nanohole arrays. Both structures support guided-mode resonance. Moreover, a 1D high-aspect ratio grating made from titanium nitride supporting Rayleigh-Woods anomalies was studied. The fabrication of the structures, as well as the biofunctionalization of their surfaces, was carried out on the basis of numerical simulation data. The optical behavior of the structures was characterized experimentally to evaluate their potential application as sensing platform. It was found that pedestal HCG structure exhibited the highest performance in terms of bulk-refractive index sensitivity of 536 nm/RIU as opposed to 482 and 409 nm/RIU of conventional and half-buried HCGs, respectively. Half-buried HCGs had the best/highest surface sensitivity. In addition, the structures were tested for the detection of two proteins: avidin and myoglobin. The limit of detection (LoD) for avidin were 236, 3.2, and 2.1 ng/mL for 2D-grating, conventional, and pedestal HCGs, respectively. For myoglobin detection, pedestal and half-buried HCG structures were selected. Half-buried structure showed slightly better results (LoD of 34.6 ng/mL against 37.3 ng/mL for pedestal HCG). Therefore, the novel design of pedestal and half-buried HCGs are proven to be promising platform for biosensing.