Polymer waveguide micro-resonators for optical biosensors

Mohd Salleh, Mohd Hazimin (2011) Polymer waveguide micro-resonators for optical biosensors. PhD thesis, University of Glasgow.

Abstract

This work describes the investigation of optical ring or disk micro-resonator as elements in label-free biosensing devices. The use of polymeric materials for micro-resonator structures recently has been gain major interest multi disciplinary research since it allows rapid and straightforward fabrication process. The aim of the work described here was to develop an optical biosensor which operates within the visible range of λ = 500 – 800 nm based on micro-resonator principle by exploiting the SU-8 polymer material.

This thesis is focused on fabrication procedures using the electron beam lithography (EBL) technology, device characterization, biological element immobilization and sensing experiments. Through the use of EBL technology, a double-cascaded gapless disk resonator (DDR) structure has been fabricated in order to significantly increase (composite) free-spectral range (FSR) to 10.0 nm from the 1.3 nm achievable with a single gapless disk resonator. The DDR structures also overcome the fabrication complexity of obtaining 50 nm gap spacing for bus waveguide to micro-resonator coupling. In order to build the device into a biological sensing platform, a biological immobilization protocol has been optimized by evaluating the degree of surface functionalization using fluorescence microscopy and X-ray photoelectron spectroscopy (XPS). Following this, to deliver the solutions required for sensing experiments, the device is integrated with a microfluidic channel system.

In experiments using sucrose solutions, linear relationship between resonance wavelength shift and refractive index of the solution was achieved with the sensitivity of 12 nm/RIU. Further experiments were performed that used specific biotin-streptavidin antibody and multiple protein binding. These showed that the device was capable of detecting immobilised biomolecules. For example, the resonance wavelength shifted by 0.43 nm following streptavidin binding. Effort also has been devoted to perform experiments on combining the spectral absorption and resonance wavelength shift analysis since this device has a capability to operate in visible wavelength region, thus exploiting strongly coloured dyes. Here, using Dylight 649® labelled streptavidin, absorption at λ = 655 nm could be detected and was accompanied by a resonance wavelength shift of 0.261 nm.

From the experiments in this thesis, the DDR device that operated within the visible wavelength region has exhibited the capability of resonance wavelength shift for label-free detection and absorption spectra analysis for optical biosensing.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Polymer micro-resonators, label-free, visible wavelength, biotin-streptavidin, spectral analysis
• Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering; Q Science > Q Science (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Cooper, Prof. Jonathan M.
• Date of Award: 2011
• Depositing User: Mr Mohd Hazimin Mohd Salleh
• Unique ID: glathesis:2011-2461
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Mar 2011
• Last Modified: 10 Dec 2012 13:55
• URI: https://theses.gla.ac.uk/id/eprint/2461