Schulich School of Engineering Research & Publications
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Browsing Schulich School of Engineering Research & Publications by Department "Mechanical & Manufacturing Engineering"
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Item Open Access Acoustic subsurface-atomic force microscopy: Three-dimensional imaging at the nanoscale(2021-01) Sharahi, Hossein J.; Janmaleki, Mohsen; Tetard, Laurene; Kim, Seonghwan; Sadeghian, Hamed; Verbiest, Gerard J.The development of acoustic subsurface atomic force microscopy, which promises three-dimensional imaging with single-digit nanometer resolution by introduction of ultrasound actuations to a conventional atomic force microscope, has come a long way since its inception in the early 1990s. Recent advances provide a quantitative understanding of the different experimentally observed contrast mechanisms, which paves the way for future applications. In this perspective, we first review the different subsurface atomic force microscope modalities: ultrasonic force microscopy, atomic force acoustic microscopy, heterodyne force microscopy, mode-synthesizing atomic force microscopy, and near-field picosecond ultrasonic microscopy. Then, we highlight and resolve a debate existing in the literature on the importance of the chosen ultrasound excitation frequencies with respect to the resonance frequencies of the cantilever and the observed contrast mechanisms. Finally, we discuss remaining open problems in the field and motivate the importance of new actuators, near-field picosecond ultrasonics, and integration with other techniques to achieve multi-functional non-destructive three dimensional imaging at the nanoscale.Item Open Access End effects of nominally two-dimensional thin flat plates(2020-09-24) Braun, Eric; Agrey, Kaden; Martinuzzi, Robert JohnDifferences in the structure and dynamics of nominally two-dimensional turbulent wakes are investigated experimentally for a thin flat plate, normal to a uniform flow, with two different end conditions: with and without end plates. Both cases are characterized by Karman-like vortex shedding with broadband low frequency unsteadiness. Both wakes evidence a low frequency flapping motion in addition to the slowly drifting base flow common to cylinder wakes. For the case without end plates, an interaction between the drift motion and the vortex formation process is associated with a much stronger modulation of the quasiperiodic vortex shedding amplitude when compared to the case with end plates where a flapping motion is more strongly expressed. These dynamics underlie structural differences in the mean wake and Reynolds stress fields. .Item Open Access Enhanced nanoplasmonic heating in standoff sensing of explosive residues with infrared reflection-absorption spectroscopy(2020-03-10) Simin, Nicholas; Park, Yangkyu; Lee, Dongkyu; Thundat, Thomas; Kim, SeonghwanVarious standoff sensing techniques employing optical spectroscopy have been developed to address challenges in safely identifying trace amounts of explosives at a distance. A flexible anodic aluminum oxide (AAO) microcantilever and a high-power quantum cascade laser utilized as the infrared (IR) source are used for standoff IR reflection-absorption spectroscopy to detect explosive residues on a metal surface. Standoff sensing of trinitrotoluene (TNT) is demonstrated by exploiting the high thermomechanical sensitivity of a bimetallic AAO microcantilever. Moreover, sputtering gold onto the fabricated AAO nanowells generates a strong scattering and absorption of IR light in the wavelength range of 5.18 μm to 5.85 μm resulting in enhanced nanoplasmonic heating. Utilizing the IR absorption enhancement in this wavelength range, the plasmonic AAO cantilever could detect TNT molecules 7 times better than the bimetallic AAO cantilever.Item Open Access Facile and rapid synthesis of functionalized Zr-BTC for the optical detection of the blistering agent simulant 2-chloroethyl ethyl sulfide (CEES)(Royal Society of Chemistry, 2021-02) Abuzalat, Osama; Homayoonnia, Setareh; Wong, Danny; Tantawy, Hesham R.; Kim, Seonghwan2-chloroethyl ethyl sulfide (CEES) is a simulant for the chemical warfare agent, bis(2-chloroethyl) sulfide, also known as mustard gas. Here, we demonstrate a facile and rapid method to synthesize a functionalized metal-organic framework (MOF) material for the detection of CEES in trace level. While Zr-BTC is synthesized, in-situ encapsulation of fluorescent material (Fluorescein) into Zr-BTC voids is performed with a simple solvothermal reaction. The produced F@Zr-BTC is used as a fluorescent probe for CEES detections. The synthesized material shows fluorescence quenching under illumination at excitation wavelength of 470 nm when the F@Zr-BTC is exposed to CEES. This sensing material shows the highest fluorescence quenching at an emission wavelength of 534 nm with CEES concentration as low as 50 ppb. Therefore, the demonstrated sensing method with F@Zr-BTC offers a fast and convenient protocol for selective and sensitive detection of CEES in practical applications.Item Open Access High-Performance, Room Temperature Hydrogen Sensing With a Cu-BTC/Polyaniline Nanocomposite Film on a Quartz Crystal Microbalance(2019-01) Abuzalat, Osama; Wong, Danny; Park, Simon S.; Kim, SeonghwanIn this paper, we demonstrate a high-performance hydrogen sensor under ambient conditions by growing a Cu-BTC/polyaniline (PANI) nanocomposite film on a quartz crystal microbalance (QCM) using intense pulsed light. The QCM was first sputter coated with a 200-nm-thin layer of copper. The copper layer was then oxidized by sodium hydroxide and ammonium persulfate. A solution containing the organic ligand (BTC) and PANI was then dropped and dried on the copper hydroxide surface of a QCM with intense pulsed light which resulted in Cu-BTC/PANI nanocomposite film on a QCM. The gas sensing performance of the Cu-BTC film and Cu-BTC/PANI composite film was compared under ambient conditions. It was found selectivity and sensitivity of the Cu-BTC/PANI nanocomposite film to hydrogen were significantly improved. In addition, a fast response time (from 2 to 5 s), operation at room temperature even in the presence of high relative humidity (up to 60%), good repeatability were achieved with the Cu-BTC/PANI nanocomposite film-grown QCM sensor.Item Open Access Machine learning strategies applied to the control of a fluidic pinball(AIP Publishing LLC, 2020-01-10) Raibaudo, Cedric; Zhong, Peng; Noack, Bernd R.; Martinuzzi, Robert JohnThe wake stabilization of a triangular cluster of three rotating cylinders is investigated. Experiments are performed at Reynolds number Re ∼ 2200. Flow control is realized using rotating cylinders spanning the wind-tunnel height. The cylinders are individually connected to identical brushless DC motors. Two-component planar particle image velocimetry measurements and constant temperature hot-wire anemometry were used to characterize the flow without and with actuation. Main open-loop configurations are studied and different controlled flow topologies are identified. Machine learning control is then implemented for the optimization of the flow control performance. Linear genetic algorithms are used here as the optimization technique for the open-loop constant speed-actuators. Two different cost functions J are considered targeting either drag reduction or wake symmetrization. The functions are estimated based on the velocity from three hot-wire sensors in the wake. It is shown that the machine learning approach is an effective strategy for controlling the wake characteristics. More significantly, the results show that machine learning strategies can reveal unanticipated solutions or parameter relations, in addition to being a tool for optimizing searches in large parameter spaces.Item Open Access Mechanisms of Friction Reduction of Nanoscale Sliding Contacts Achieved Through Ultrasonic Excitation(IOP Publishing Ltd, 2018-10) Sharahi, Hossein J; Egberts, Philip; Kim, SeonghwanFriction reduction is an important issue for proper functioning of nano-/micro-electromechanical systems (N-/MEMS) due to their large surface to volume ratios and the inability of traditional liquid lubricants to effectively lubricate sliding contacts. One efficient technique to achieve substantially lowered friction at nanoscale, as well as superlubricity in some instances, was investigated with the coupling of ultrasonic actuation of the sliding contact in an atomic force microscope (AFM). Despite the successful application of ultrasonic AFM methods in achieving mechanical property measurements and nanoscale subsurface imaging of soft and hard materials, the mechanism of friction reduction in the microscopic contact and the influence of the ultrasonic parameters on friction reduction are still elusive. In this study, the effects of excitation amplitude, applied normal force, tip radius, and humidity on friction have been investigated in detail. Ultrasonic force microscopy (UFM) results are compared against those collected with conventional contact-AFM (C-AFM) and indicate that a reduction in the adhesive interaction between the tip and sample, as well as a reduction in the shear strength can explain the mechanisms of the friction reduction in UFM method. This study opens up a new door for the control of friction and wear, which is critical for the increased lifetime of AFM probes, N-/MEMS devices and would potentially bridge the gap between nanotribology and other fields, such as nanomachining, nanolithography and biomaterials imaging.Item Open Access Rapid Fabrication of Metal–Organic Framework Films from Metal Substrates Using Intense Pulsed Light(2018-01) Yim, Changyong; Abuzalat, Osama; Elsayed, Mohamed; Park, Simon; Kim, SeonghwanIn this article, we demonstrate an innovative approach for the fabrication of uniform metal–organic framework (MOF) films on Cu or Zn metal substrates by using intense pulsed light (IPL). The metal substrates are first treated with a strong oxidizing agent to convert the metal to the corresponding metal hydroxide, then MOF films are prepared by in situ growth over the metal hydroxide surface with an organic ligand by multiple IPL irradiations at room temperature and ambient conditions. The metal hydroxide absorbs the light from IPL, which discharges an excessive energy with relatively short pulse duration (milliseconds), then converts the light to thermal energy. Four well-known MOF compounds, Cu-BTC, Cu-BDC, ZIF-8, and MOF-5 film, are successfully synthesized and characterized by scanning electron microscopy and X-ray diffraction analysis. The effects of organic ligand concentration and IPL exposure time on MOF film synthesis are systematically investigated. The innovative fabrication method presented in this study offers many advantages such as short processing time, low cost process under ambient conditions, less use of consumable chemicals, and applicability to fabrication of other MOF films.Item Open Access Sonochemical fabrication of Cu(II) and Zn(II) metal-organic framework films on metal substrates(2018-07) Abuzalat, Osama; Wong, Danny; Elsayed, Mohamed; Park, Simon; Kim, SeonghwanIn this article, we demonstrate a rapid and facile method for in-situ growth of metal-organic framework (MOF) films on Cu or Zn metal substrates by sonochemical techniques. The substrates were first treated with a strong oxidizing agent to convert the metal to the corresponding metal hydroxide. Ultrasonic irradiation provided the energy to drive the reaction between the metal ion sources and organic ligands. Four MOF films (Cu-BTC, Cu-BDC, ZIF-8 and MOF-5) were successfully fabricated by this approach. The produced films were characterized by scanning electron microscopy and X-ray diffraction analysis. The effects of organic ligand concentration and ultrasonic irradiation time on MOF film synthesis were also systematically investigated. The rapid and facile fabrication method presented in this article could serve a new route to grow MOF films on various gas sensor surfaces. Of the MOF films, ZIF-8 film was tested as a potential methane sensor.