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

Observations of phase changes in monoolein during high viscous injection

Serial crystallography of membrane proteins often employs high-viscosity injectors (HVIs) to deliver micrometre-sized crystals to the X-ray beam. Typically, the carrier medium is a lipidic cubic phase (LCP) media, which can also be used to nucleate and grow the crystals. However, despite the fact that the LCP is widely used with HVIs, the potential impact of the injection process on the LCP structure has not been reported and hence is not yet well understood. The self-assembled structure of the LCP can be affected by pressure, dehydration and temperature changes, all of which occur during continuous flow injection. These changes to the LCP structure may in turn impact the results of X-ray diffraction measurements from membrane protein crystals. To investigate the influence of HVIs on the structure of the LCP we conducted a study of the phase changes in monoolein/water and monoolein/buffer mixtures during continuous flow injection, at both atmospheric pressure and under vacuum. The reservoir pressure in the HVI was tracked to determine if there is any correlation with the phase behaviour of the LCP. The results indicated that, even though the reservoir pressure underwent (at times) significant variation, this did not appear to correlate with observed phase changes in the sample stream or correspond to shifts in the LCP lattice parameter. During vacuum injection, there was a three-way coexistence of the gyroid cubic phase, diamond cubic phase and lamellar phase. During injection at atmospheric pressure, the coexistence of a cubic phase and lamellar phase in the monoolein/water mixtures was also observed. The degree to which the lamellar phase is formed was found to be strongly dependent on the co-flowing gas conditions used to stabilize the LCP stream. A combination of laboratory-based optical polarization microscopy and simulation studies was used to investigate these observations