Faculty of Applied Science and Engineering

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Established in 1873, the Faculty of Applied Science and Engineering is Canada’s largest engineering school and is widely recognized as one of the best in North America. Research plays the central role in the University of Toronto’s international reputation, and graduate students are an integral part of our ongoing success. The Faculty of Applied Science and Engineering currently has more than 1,400 graduate students and 4,300 undergraduate students taught by 219 faculty members.

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Now showing 1 - 20 of 2055

0D-2D Quantum Dot: Metal Dichalcogenide Nanocomposite Photocatalyst Achieves Efficient Hydrogen Generation
(Wiley, 2017-04-11) Liu, Xiao-Yuan; Chen, Hao; Wang, Ruili; Shang, Yuequn; Zhang, Qiong; Li, Wei; Zhang, Guozhen; Su, Juan; Dinh, Cao Thang; de Arquer, F Pelayo García; Li, Jie; Jiang, Jun; Mi, Qixi; Si, Rui; Li, Xiaopeng; Sun, Yuhan; Long, Yi-Tao; Tian, He; Sargent, Edward H; Ning, Zhijun
Hydrogen generation via photocatalysis-driven water splitting provides a convenient approach to turn solar energy into chemical fuel. The development of photocatalysis system that can effectively harvest visible light for hydrogen generation is an essential task in order to utilize this technology. Herein, a kind of cadmium free Zn-Ag-In-S (ZAIS) colloidal quantum dots (CQDs) that shows remarkably photocatalytic efficiency in the visible region is developed. More importantly, a nanocomposite based on the combination of 0D ZAIS CQDs and 2D MoS2 nanosheet is developed. This can leverage the strong light harvesting capability of CQDs and catalytic performance of MoS2 simultaneously. As a result, an excellent external quantum efficiency of 40.8% at 400 nm is achieved for CQD-based hydrogen generation catalyst. This work presents a new platform for the development of high-efficiency photocatalyst based on 0D-2D nanocomposite.
10.6% Certified Colloidal Quantum Dot Solar Cells via Solvent-Polarity-Engineered Halide Passivation
(American Chemical Society, 2016-06-28) Lan, Xinzheng; Voznyy, Oleksandr; García de Arquer, F. Pelayo; Liu, Mengxia; Xu, Jixian; Proppe, Andrew H.; Walters, Grant; Fan, Fengjia; Tan, Hairen; Liu, Min; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H.
Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaics with broad spectral absorption tunability. Major advances in their efficiency have been made via improved CQD surface passivation and device architectures with enhanced charge carrier collection. Herein, we demonstrate a new strategy to improve further the passivation of CQDs starting from the solution phase. A cosolvent system is employed to tune the solvent polarity in order to achieve the solvation of methylammonium iodide (MAI) and the dispersion of hydrophobic PbS CQDs simultaneously in a homogeneous phase, otherwise not achieved in a single solvent. This process enables MAI to access the CQDs to confer improved passivation. This, in turn, allows for efficient charge extraction from a thicker photoactive layer device, leading to a certified solar cell power conversion efficiency of 10.6%, a new certified record in CQD photovoltaics.
A 2.5-V 45-Gb/s decision circuit using SiGe BiCMOS logic
(IEEE, 2005) Voinigescu, Sorin; Dickson, Timothy O; Beerkens, Rudy
2D Hybrid Perovskites Employing an Organic Cation Paired with a Neutral Molecule
(ACS, 2023-12-20) Najarian, Amin Morteza; Vafaie, Maral; Sabatini, Randy; Wang, Sasa; Li, Peng; Xu, Shihong; Saidaminov, Makhsud I; Hoogland, Sjoerd; Sargent, Edward H
Two-dimensional (2D) hybrid perovskites harness the chemical and structural versatility of organic compounds. Here, we explore 2D perovskites that incorporate both a first organic component, a primary ammonium cation, and a second neutral organic module. Through the experimental examination of 42 organic pairs with a range of functional groups and organic backbones, we identify five crystallization scenarios that occur upon mixing. Only one leads to the cointercalation of the organic modules with distinct and extended interlayer spacing, which is observed with the aid of X-ray diffraction (XRD) pattern analysis combined with cross-sectional transmission electron microscopy (TEM) and elemental analysis. We present a picture in which complementary pairs, capable of forming intermolecular bonds, cocrystallize with multiple structural arrangements. These arrangements are a function of the ratio of organic content, annealing temperature, and substrate surface characteristics. We highlight how noncovalent bonds, particularly hydrogen and halogen bonding, enable the influence over the organic sublattice in hybrid halide perovskites.
2D matrix engineering for homogeneous quantum dot coupling in photovoltaic solids
(Nature Publishing Group, 2018-04-23) Xu, Jixian; Voznyy, Oleksandr; Liu, Mengxia; Kirmani, Ahmad R; Walters, Grant; Munir, Rahim; Abdelsamie, Maged; Proppe, Andrew H; Sarkar, Amrita; García de Arquer, F Pelayo; Wei, Mingyang; Sun, Bin; Liu, Min; Ouellette, Olivier; Quintero-Bermudez, Rafael; Li, Jie; Fan, James; Quan, Lina; Todorovic, Petar; Tan, Hairen; Hoogland, Sjoerd; Kelley, Shana O; Stefik, Morgan; Amassian, Aram; Sargent, Edward H
Colloidal quantum dots (CQDs) are promising photovoltaic (PV) materials because of their widely tunable absorption spectrum controlled by nanocrystal size1,2. Their bandgap tunability allows not only the optimization of single-junction cells, but also the fabrication of multijunction cells that complement perovskites and silicon 3 . Advances in surface passivation2,4-7, combined with advances in device structures 8 , have contributed to certified power conversion efficiencies (PCEs) that rose to 11% in 2016 9 . Further gains in performance are available if the thickness of the devices can be increased to maximize the light harvesting at a high fill factor (FF). However, at present the active layer thickness is limited to ~300 nm by the concomitant photocarrier diffusion length. To date, CQD devices thicker than this typically exhibit decreases in short-circuit current (JSC) and open-circuit voltage (VOC), as seen in previous reports3,9-11. Here, we report a matrix engineering strategy for CQD solids that significantly enhances the photocarrier diffusion length. We find that a hybrid inorganic-amine coordinating complex enables us to generate a high-quality two-dimensionally (2D) confined inorganic matrix that programmes internanoparticle spacing at the atomic scale. This strategy enables the reduction of structural and energetic disorder in the solid and concurrent improvements in the CQD packing density and uniformity. Consequently, planar devices with a nearly doubled active layer thicknesses (~600 nm) and record values of JSC (32 mA cm-2) are fabricated. The VOC improved as the current was increased. We demonstrate CQD solar cells with a certified record efficiency of 12%.
2D Metal Oxyhalide-Derived Catalysts for Efficient CO2 Electroreduction
(Wiley Online Publishing, 2018-08-08) García de Arquer, F Pelayo; Bushuyev, Oleksandr S; De Luna, Phil; Dinh, Cao-Thang; Seifitokaldani, Ali; Saidaminov, Makhsud I; Tan, Chih-Shan; Quan, Li Na; Proppe, Andrew; Kibria, Md Golam; Kelley, Shana O; Sinton, David; Sargent, Edward H
Electrochemical reduction of CO2 is a compelling route to store renewable electricity in the form of carbon-based fuels. Efficient electrochemical reduction of CO2 requires catalysts that combine high activity, high selectivity, and low overpotential. Extensive surface reconstruction of metal catalysts under high productivity operating conditions (high current densities, reducing potentials, and variable pH) renders the realization of tailored catalysts that maximize the exposure of the most favorable facets, the number of active sites, and the oxidation state all the more challenging. Earth-abundant transition metals such as tin, bismuth, and lead have been proven stable and product-specific, but exhibit limited partial current densities. Here, a strategy that employs bismuth oxyhalides as a template from which 2D bismuth-based catalysts are derived is reported. The BiOBr-templated catalyst exhibits a preferential exposure of highly active Bi ( 11¯0 ) facets. Thereby, the CO2 reduction reaction selectivity is increased to over 90% Faradaic efficiency and simultaneously stable current densities of up to 200 mA cm-2 are achieved-more than a twofold increase in the production of the energy-storage liquid formic acid compared to previous best Bi catalysts.
A 3-V Fully Differential Distributed Limiting Driver for 40-Gb/s Optical Transmission Systems
(IEEE, 2003) Voinigescu, Sorin ; McPherson, Douglas S. ; Pera, Florin ; Tazlauanu, Mihai
The $30,000 hydro development
(2009-10) Gordon, J.L.
30-100-GHz inductors and transformers for millimeter-wave (Bi)CMOS integrated circuits
(IEEE, 2005) Voinigescu, Sorin ; Dickson, Timothy O ; LaCroix, Marc-Andre ; Boret, Samuel ; Gloria, Daniel ; Beerkens, Rudy
3D dose prediction for Gamma Knife radiosurgery using deep learning and data modification
(2023-02) Zhang, Binghao; Babier, Aaron; Chan, Timothy C Y; Ruschin, Mark
To develop a machine learning-based, 3D dose prediction methodology for Gamma Knife (GK) radiosurgery. The methodology accounts for cases involving targets of any number, size, and shape.
3D printed geometrically tessellated sheets with origami-inspired patterns
(SAGE Publishing, 2022-03) Wickeler, Anastasia L.; Naguib, Hani E.
This study demonstrates that the impact energy absorption capabilities of flexible sheets can be significantly enhanced by implementing tessellated designs into their structure. Configurations of three tessellated geometries were tested; they included a triangular-based, a rectangular-based, and a novel square-based pattern. Due to their geometrical complexity, multiple configurations of these tessellations were printed from a rubber-like material using an inkjet printer with 2 different thicknesses (2 and 4 mm), and their ability to absorb impact energy was compared to an unpatterned inkjet-printed sheet. In addition, the effect of multi-sheets stacking was also tested. Due to the tailored structure, the impact testing showed that the single layer sheets were more effective at absorbing impact loads, and experience less deformation, than their two-layer counterparts. The 4 mm thick tessellated patterns were most effective at absorbing impact loads; all three thick patterns measured about 40% lower impact forces transferred to the base of the samples compared to the unpatterned counterparts.
3D printing complex lattice structures for permeable liver phantom fabrication
(2018) Low, Linda; Ramadan, Sherif; Coolens, Catherine; Naguib, Hani E.
Liver cancer is currently the third deadliest cancer in the world, affecting over 700,000 people per year. To improve early detection of tumours, perfusion testing is used for imaging of blood flow in the liver. Creating a phantom to accurately mimic the liver in imaging techniques such as Dynamic Contrast-enhanced (DCE) computed tomography (CT) will improve testing and calibration of different imaging protocols and pharmacokinetic perfusion models. In current literature, there lacks a permeable, easily producible and reusable liver phantom for dynamic contrast-enhanced CT perfusion testing. This study details the production of phantoms with controllable permeability for standardization in hepatic perfusion using commercially available 3D printing methods. Phantoms with hexagonal channels were designed in nTopology Element and printed in materials with a density of 0.9–1.5 g/cm3. Polylactic acid was selected for fused deposition modelling (FDM), while proprietary resins were used for an inkjet printing process called MultiJet Printing (MJP). Permeability tests were performed on samples to observe flow rates obeying Darcy's Law. Scanning electron microscopy (SEM) was used to analyze pore size in FDM and MJP samples, while micro-CT scans were performed to analyze pore interconnectivity. The collected permeability data exceeds reported literature values of 0.0167 mL s−1 cm2 and approach the desired range of 0.15–0.3 mL s−1 cm2. Micro-CT scans show obstructions from the MJP printing process. SEM images were analyzed in Fiji and showed varying results for FDM printing. Future work will involve reducing pore size while maintaining high permeability. Using 3D printing in phantom development will help create adaptable, reliable and permeable phantoms for diagnostic imaging.
3D‐Knit Dry Electrodes using Conductive Elastomeric Fibers for Long‐Term Continuous Electrophysiological Monitoring
(Wiley, 2022) Eskandarian, Ladan; Toossi, Amirali; Nassif, Farah; Golmohammadi Rostami, Sahar; Ni, Siting; Mahnam, Amin; Alizadeh Meghrazi, Milad; Takarada, Wataru; Kikutani, Takeshi; Naguib, Hani E.
Recent advances in telemedicine and personalized healthcare have motivated new developments in wearable technologies targeting continuous monitoring of biosignals. Common limitations of wearables for continuous monitoring include durability and breathability of their biopotential electrodes. This paper tackles this challenge by proposing flexible, breathable, and washable dry textile electrodes made of conductive elastomeric filaments (CEFs). First, candidate CEF fibers are characterized. Using an industrial knitting machine, CEF fibers are then directly knitted into textile electrodes. To assess their performance in more realistic circumstances, smart garments with textile electrodes are knitted. Electrocardiograms (ECGs) are acquired using an underwear garment and electrooculograms (EOGs) are acquired using a headband. ECGs and EOGs with textile electrodes are found to have comparable fidelity to that of the gold standard gel electrodes. CEF electrodes are also resistant to repeated wash and dry cycles (30×) and continue to acquire high-fidelity biosignals. Smart underwear garments are also used to perform continuous ECG measurements in five participants over 24 h of unrestricted daily activities. Results demonstrate the success of these garments in performing high fidelity continuous ECG monitoring. Collectively, these results present CEF electrodes as a promising scalable solution to the challenges of wearable technologies for long-term continuous electrophysiological monitoring applications.
3D-Printable Fluoropolymer Gas Diffusion Layers for CO2 Electroreduction
(Wiley, 2021-01-14) Wicks, Joshua; Jue, Melinda L; Beck, Victor A; Oakdale, James S; Dudukovic, Nikola A; Clemens, Auston L; Liang, Siwei; Ellis, Megan E; Lee, Geonhui; Baker, Sarah E; Duoss, Eric B; Sargent, Edward H
The electrosynthesis of value-added multicarbon products from CO2 is a promising strategy to shift chemical production away from fossil fuels. Particularly important is the rational design of gas diffusion electrode (GDE) assemblies to react selectively, at scale, and at high rates. However, the understanding of the gas diffusion layer (GDL) in these assemblies is limited for the CO2 reduction reaction (CO2 RR): particularly important, but incompletely understood, is how the GDL modulates product distributions of catalysts operating in high current density regimes > 300 mA cm-2 . Here, 3D-printable fluoropolymer GDLs with tunable microporosity and structure are reported and probe the effects of permeance, microstructural porosity, macrostructure, and surface morphology. Under a given choice of applied electrochemical potential and electrolyte, a 100× increase in the C2 H4 :CO ratio due to GDL surface morphology design over a homogeneously porous equivalent and a 1.8× increase in the C2 H4 partial current density due to a pyramidal macrostructure are observed. These findings offer routes to improve CO2 RR GDEs as a platform for 3D catalyst design.
4D-printed hybrids with localized shape memory behaviour: Implementation in a functionally graded structure
(Nature Research, 2019-12-10) Sun, Yu-Chen; Wan, Yimei; Nam, Ryan; Chu, Marco; Naguib, Hani E
4D-printed materials are an emerging field of research because the physical structure of these novel materials respond to environmental changes. 3D printing techniques have been employed to print a base material with shape memory properties. Geometrical deformations can be observed once an external stimulus triggers the shape memory effect (SME) integrated into the material. The plasticizing effect is a well-known phenomenon where the microscopic polymer chain movements have been altered and reflected in different shape memory behaviour. It has been suggested that a 4D material with localized actuation behaviour can be fabricated by utilizing functionally graded layers made from different degrees of plasticizing. This study demonstrated that a novel 4D material can be fabricated from material extraction continuous printing technique with different loadings of poly(ethylene glycol) (PEG) plasticize, achieving localized thermal recovery. The results indicate that a plasticized functional layer is an effective technique for creating next generation 4D materials.
6-kΩ 43-Gb/s differential transimpedance-limiting amplifier with auto-zero feedback and high dynamic range
(IEEE, 2004) Voinigescu, Sorin ; Tran, Hai ; Pera, Florin ; McPherson, Douglas S. ; Viorel, Doren
An 80-Gb/s 231-1 pseudorandom binary sequence generator in SiGe BiCMOS technology
(IEEE, 2005) Voinigescu, Sorin ; Dickson, Timothy O ; Laskin, Ekaterina ; Khalid, Imran ; Beerkens, Rudy ; Xie, Jingqiong ; Karajica, Boris
A CFD Study of the Effects of Rings on Flow and Temperature in Lime Kilns
(2020-03) Gareau, Patrick Raymond; Bussmann, Markus; Tran, Honghi N; Mechanical and Industrial Engineering
Rotary lime kilns, used in the kraft chemical recovery process to convert lime mud into lime, suffer from the formation of ring-shaped deposits called rings. Prior research has led to better understanding of ring growth, although it is still not fully understood, since the process is concealed within the kiln. For this reason, a steady state, 2D axisymmetric lime kiln, ring, and virtual bed heat sink model has been developed in this work, and was validated by predicting the shell temperature of a real kiln with good accuracy. Various ring configurations were then simulated in a typical lime kiln in order to study their effects on flow and temperature. The results show that ring-related jets and recirculation zones form in the gas, temperature deviations occur upstream and downstream of the rings, and, recarbonation, causing ring hardening, occurs over a wide range of ring thickness for both front-end and mid-kiln rings.
A Comparative Study of the Electro-dewatering of Pulp and Paper Mill Biosludge
(2019-11) Arakelian, Raphael Joseph Gregory; Allen, David G; Tran, Honghi N; Chemical Engineering Applied Chemistry
The activated sludge process, often used in pulp and paper mills, generates biosludge that requires dewatering. Wastewater treatment practices and upstream processes impact biosludge characteristics, including dewaterability. Electro-dewatering, compared to other dewatering methods, has a high dewatering potential while requiring low amounts of energy. The main objective of this study was to determine the variation in the characteristics of mill biosludge and its impact on electro-dewatering. Biosludge was sampled from four different wastewater treatment plants, including a municipal one as cross-reference, and characterized for various properties. Using a bench-scale electro-dewatering device, thickened biosludge was subjected to constant-voltage electro-dewatering at 20 V. Electro-dewatering successfully removed 68-74% of the water while consuming between 0.15 and 0.56 kWh/kg additional water removed. Overall, varying biosludge characteristics did not impact the total amount of water removed, but certain characteristics, particularly the electrical conductivity, dictated the routes of water removal (evaporation, filtration) and energy consumption.
A Field Study of Exterior Airtightness Testing in Five Multi-Unit Residential Buildings
(2018-11) Gray, Jason; Touchie, Marianne; Civil Engineering
The airtightness of a multi-unit residential building (MURB) enclosure is an important factor when considering energy consumption. There is limited data available on the airtightness of MURBs. The complexity of the MURB geometry complicate standard testing procedures; this is especially true when measuring the isolated exterior enclosure airtightness where the adjacent zones must be taken into consideration. This thesis explored three alternative suite-based methods from the literature used to measure the isolated exterior pressure boundary leakage. A field study took place in five MURBs where the goal was to compare the results from these methods to pressure neutralization test results. Of the three testing methods, the testing method that used adjacent pressure differentials in its calculation was the most similar. Ideally, these results and lessons learned will aid future researchers in developing airtightness testing methods and standards for conducting efficient and accurate tests.

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