14 research outputs found
Microfabricated Formaldehyde Gas Sensors
Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based detection, enzyme-based electrochemical sensors, and nanowire-based sensors. This paper also investigates the promise of polymer-based sensors for low-temperature, low-power operation
Enhancing the performance of silicon photonics biosensors
Silicon photonic biosensors have the potential to transform medical diagnostics and healthcare delivery. Hundreds of these nano-scale sensors can be integrated onto a single millimeter-sized silicon substrate. They are fabricated in established CMOS foundries leveraging similar economies-of-scale achieved by electronic integrated circuits. This also enables their potential integration with electronic read out circuitry on a single chip. As near-infrared light propagates through nanoscale silicon wires, a portion of the light resides outside the waveguide interacting with biomolecules on the waveguide’s surface. While silicon photonic biosensors have demonstrated performances approaching today’s gold-standard diagnostic, the enzyme-linked immunosorbent assay (ELISA), improving their performance expands the potential use for applications requiring higher sensitivities and detection limits. To this end, this thesis describes efforts to optimize established biosensor configurations and develop novel structures with performance that exceeds commercially available silicon photonic biosensor platforms. This involves improving the bulk and surface sensitivity, detection limit, and quality factor of transverse electric (TE) and magnetic (TM) mode resonators in various waveguide topologies. Specifically, TM mode microring resonators, microdisk resonators, thin waveguide resonators, and the first of its kind sub-wavelength grating microring resonator with a 10X sensitivity improvement over today’s commercially available ring resonators are presented. Furthermore the use novel TE mode slot-waveguide and TM mode strip waveguide Bragg gratings which facilitate higher sensitivities (8X) and lower detection limits for biosensing applications are described. Finally, suspended Bragg grating structures are investigated to further improve sensitivity. To support the design and characterization efforts required to efficiently investigate many different sensors, a testing platform and process design kit (PDK) was developed. The test platform automatically tests hundreds of devices and orchestrates complex, multi-hour assays. The PDK reduces first-time design risk and expedites chip testing. Both have been open-sourced and are in use by more than a dozen academic and commercial research groups in various countries.Applied Science, Faculty ofGraduat
Experimental performance of DWDM quadruple Vernier racetrack resonators,” Opt
Abstract: We demonstrate that one can meet numerous commercial requirements for filters used in dense wavelength-division multiplexing applications using quadruple Vernier racetrack resonators in the silicon-oninsulator platform. Experimental performance shows a ripple of 0.2 dB, an interstitial peak suppression of 39.7 dB, an adjacent channel isolation of 37.2 dB, an express channel isolation of 10.2 dB, and a free spectral range of 37.52 nm
Cascaded silicon-on-insulator microring resonators for the detection of biomolecules in PDMS microfluidic channel
Silicon-On-Insulator (SOI) photonic microring resonators have shown promising potential for real time detection of biomolecules because of the
sensitivity towards surface binding events. Previous work shows the use of single ring resonators for sensing applications. Each ring requires
an input and output coupler and can be addressed only one at a time. We propose a novel use of cascaded ring resonators (width w = 200 nm and
bending Radius R = 30 µm) together with a PDMS microfluidic network fabricated by soft lithography to expose each ring individually with
different solutions. The SOI substrate with the planar waveguides and the PDMS with the microchannels are reversibly bonded to each other. The
use of cascaded ring resonators offers the possibility to measure transmission spectra of multiple rings in different channels simultaneously.
We measured Q-factors of >30'000 in air and >10'000 when exposed to water. Using a water/glycerin solution with known refractive indices we
determine the sensitivity to be ~40 nm/RIU.
Copyright 2011 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofReviewedFacult
Silicon photonic resonator sensors and devices.
Silicon photonic resonators, implemented using silicon-on-insulator substrates, are promising for numerous applications. The most
commonly studied resonators are ring/racetrack resonators. We have fabricated these and other resonators including disk resonators,
waveguide-grating resonators, ring resonator reflectors, contra-directional grating-coupler ring resonators, and racetrack-based
multiplexer/demultiplexers. While numerous resonators have been demonstrated for sensing purposes, it remains unclear as to which
structures provide the highest sensitivity and best limit of detection; for example, disc resonators and slot-waveguide-based ring
resonators have been conjectured to provide an improved limit of detection. Here, we compare various resonators in terms of sensor
metrics for label-free bio-sensing in a micro-fluidic environment. We have integrated resonator arrays with PDMS micro-fluidics for
real-time detection of biomolecules in experiments such as antigen-antibody binding reaction experiments using Human Factor IX
proteins. Numerous resonators are fabricated on the same wafer and experimentally compared. We identify that, while evanescent-field
sensors all operate on the principle that the analyte's refractive index shifts the resonant frequency, there are important differences
between implementations that lie in the relationship between the optical field overlap with the analyte and the relative contributions
of the various loss mechanisms. The chips were fabricated in the context of the CMC-UBC Silicon Nanophotonics Fabrication course and
workshop. This yearlong, design-based, graduate training program is offered to students from across Canada and, over the last four
years, has attracted participants from nearly every Canadian university involved in photonics research. The course takes students
through a full design cycle of a photonic circuit, including theory, modelling, design, and experimentation
Copyright 2012 Society of Photo-Optical Instrumentation Engineers.
One print or electronic copy may be made for personal use only. Systematic reproduction and distribution,
duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.Applied Science, Faculty ofChemical and Biological Engineering, Department ofElectrical and Computer Engineering, Department ofReviewedFacult