Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Thermal-AFM under aqueous environment

The aim of this thesis is to describe the work developing and demonstrating the use of Scanning Thermal Microscopy (SThM) in an aqueous electrically conductive environment for the first time. This has been achieved by using new instrumentation to allow conventional SThM probes to measure and manipulate the temperature of non-biological and biological samples. For the latter, the aqueous environment is crucial to allow in-vitro experimentation, which is important for the future use of SThM in the life sciences. SThM is known to be a powerful technique able to acquire simultaneous topographic and thermal images of samples. It is able to measure the microscopic thermal properties of a surface with nanoscale spatial resolution. However, SThM has traditionally been limited to use in vacuum, air and electrically inert liquids. The aqueous Scanning Thermal Microscopy (a-SThM) described in this thesis is an entirely novel technique that opens up a new field for thermal-AFM. The first challenge addressed in this work was the adaptation of a commercial Multimode Nanoscope IIIa AFM to permit electrical access to a SThM probe completely immersed in aqueous solutions. By employing a newly designed probe holder and electronic instrumentation, the probe could then be electrically biased without inducing electrochemical reactions. This approach permitted conventional microfabricated thermal probes to be operated whilst fully immersed in water. This innovation allowed SThM measurements under deionized (DI) water to be performed on a simple solid sample (Pt on Si3N4) and the results compared with in-air scans and accurate 3D Finite Element (FE) simulations. Once the validity of the technique was proven, its performance was investigated, including crucially the limit of its thermal-spatial resolution; this was investigated using nanofabricated solid samples (Au on Si3N4) with well-defined features. These results were compared to the FE model, allowing an understanding of the mechanisms limiting resolution to be developed. In order to demonstrate the advantages granted by the water’s superior thermal conductivity compared to air or other liquids, non-contact thermal images were also acquired using the same samples. The final part of this thesis was focused on extending SThM into the biological area; a completely new field for this technique. New results are presented for soft 4 samples: I-collagen gel and collagen fibrils, which were thermally manipulated using a self-heated SThM probe. This successfully demonstrated the possibility of using heat to alter a biological sample within a very well localised area while being operated for long time in an aqueous environment. The difference in force response originated from the AFM scans with different levels of self-heating further proved the robustness of the technique. Finally, the technique was employed to study MG-63 living cells: The SThM probe was left in contact with each cell for a pre-determined period of time, with and without self heating. The results demonstrated that only the heated cells, directly beneath the probe tip died, tallying with the highly localised temperature gradient predicted by FE analysis

Proceedings of the Scientific-Practical Conference "Research and Development - 2016"

talent management; sensor arrays; automatic speech recognition; dry separation technology; oil production; oil waste; laser technolog

Dielectric barrier discharges : a promising tool for the fabrication of anti-fogging coatings

La « vue floue » typique des surfaces embuées peut être extrêmement frustrante. Des exemples tels que les lunettes qui s’embuent pendant l’activité physique, la condensation qui se forme à l’intérieur des fenêtres pendant l’hiver ou les miroirs qui se couvrent de buée pendant la douche le démontrent. En outre, la présence de buée sur les surfaces cause des effets néfastes dans certains secteurs d’activité comme l’industrie automobile (pare-brise et rétroviseurs), l’industrie optique (objectifs, caméras, télescopes et capteurs), l’industrie solaire (modules photovoltaïques), l’industrie alimentaire (emballages d’aliments) et le secteur médical (lunettes et endoscopes). Au cours de la dernière décennie, l’application de revêtements (super)hydrophiles a suscité un intérêt croissant, en raison de leur capacité d’atténuer les effets de la buée. Leur principe de fonctionnement repose sur l’utilisation de matériaux interagissant avec les gouttes d’eau pour en modifier leur morphologie, générant une couche mince d’eau sur la surface. Ainsi, la lumière incidente n’est pas dispersée et les effets de la buée sont amoindris. Jusqu’à présent, la plupart des techniques de dépôt explorées pour produire des revêtements (super) hydrophiles sont inaccessibles à la production de masse en raison de leur nature multiétape. Pour cette raison, l’exploration de techniques adaptées à ce type de production, telles que les décharges à barrière diélectrique à pression atmosphérique (AP-DBD), un type de procédé de dépôt chimique en phase vapeur assisté par plasma (AP-PECVD), est cruciale afin d’élargir l’utilisation des revêtements antibuée au-delà du laboratoire. Dans un procédé AP-PECVD contrôlé par des barrières diélectriques (AP-DBD), certains précurseurs inorganiques ou organométalliques (e.g., TiCl4, TiN, SiH4, Si2O(CH3)2) sont introduits entre deux électrodes parallèles avec un gaz vecteur (e.g., N2, Ar, He) à la pression atmosphérique, où ils se fragmentent à la suite d’interactions avec les espèces du plasma. Les fragments résultants réagissent les uns avec les autres ou avec le substrat afin de produire les espèces réactives requises au dépôt du revêtement. Les caractéristiques structurelles et fonctionnelles des revêtements PECVD (e.g., la rugosité de surface, la biocompatibilité, les propriétés optiques et de mouillage) dépendent des certains paramètres de dépôt, tels que la puissance dissipée dans la décharge, le type de décharge, la concentration de précurseurs et le débit de gaz. La possibilité de se procurer des échantillons de verre dotés de la propriété antibuée via APPECVD a été démontrée dans cette thèse. En contrôlant les paramètres de dépôt, les revêtements antibuée ont été préparés en utilisant du 1,3,5,7-tétraméthylcyclotétrasiloxane (Si4O4H4(CH3)4) et de l’oxyde nitreux (N2O) au moyen d’une DBD fonctionnant en N2 à la pression atmosphérique. Dans le cas des revêtements fabriqués dans des conditions statiques (aucun mouvement entre l’échantillon de verre et les électrodes), l’évaluation quantitative de la résistance à la buée (ASTM F 659-06) a révélé que les revêtements obtenus avec un rapport [N2O]/[TMCTS] ³ 30 ou avec une puissance dissipée ³ 0,25 W cm-2 sont antibuée (transmittance > 80%) en raison de leur nature hydrophile. La quantité de précurseur et d’oxydant injectée dans la décharge, exprimée par la somme « [N2O] + [TMCTS] », n’agissait que peu sur la performance antibuée. En l’absence de changements significatifs dans la rugosité de surface (Rrms et Ra étant compris entre 3 et 6 nm), l’origine de la performance antibuée a été attribuée à la chimie de surface. Couplé aux rapports O/Si (résultats XPS), un paramètre arbitraire, appelé « rapport d’embuage » a été défini en considérant les résultats FTIR pour expliquer les performances antibuée observées. On a pu constater qu’un rapport O/Si ≥ 2,3 couplé à un rapport d’embuage dans l’intervalle de 0-0,10, résultant de la présence de fonctionnalités hydrophiles, telles que les groupes silanol, hydroxyle, carboxyle or ester à la surface étaient nécessaires pour atteindre la propriété antibuée. Par ailleurs, les revêtements préparés dans des conditions dynamiques utilisant trois autres précurseurs aux structures différentes quant à la présence d’un cycle et au nombre de groupes Si-H et Si-CH3 (l’octaméthylcyclotétrasiloxane, le 1,1,3,3-tétraméthyldisiloxane et l’hexaméthyldisiloxane) n’étaient pas antibuée. Ce résultat porte à croire que la structure cyclique du TMCTS et la forte réactivité des liaisons Si-H est à l’origine de la formation de ces fonctionnalités hydrophiles et par conséquent, à la performance antibuée observée dans les verres traités en injectant du TMCTS dans la décharge plasma.Experience shows that the “blurred view” typical of fogged surfaces can be incredibly frustrating. Eyewear fogging up during physical activity, condensation forming on the inside of windows during the winter, or bathroom mirrors steaming up when taking a shower are some obvious examples. In addition to being upsetting, the fogging of surfaces has been reported to cause adverse effects on sectors of activity as diverse as the automotive industry (e.g., windshield glass and rearview mirrors), the optical industry (e.g., lenses, cameras, telescopes, and sensors), the solar industry (e.g., photovoltaic modules), the food industry (e.g., food packaging), and medicine (e.g., goggles and endoscopes). Over the last decade, interest has been growing in the application of hydrophilic and superhydrophilic coatings, as they can efficiently mitigate the effects of fogging by changing the morphology of fog drops. The working principle of a (super)hydrophilic surface is based on the use of materials producing a thin film of water on the solid surface on interaction with fog drops. As a result, incident light transmits without being scattered and the effects of fogging are minimized. Unfortunately, most of the deposition techniques used thus far for the fabrication of (super)hydrophilic coatings involves multiple steps, thus making their integration into mass production a challenging task. For this reason, the exploration of deposition techniques adapted for large-scale production is crucial to broaden the range of application of antifogging coatings beyond the laboratory. In this regard, numerous studies on the use of dielectric barriers in plasma enhanced chemical vapor deposition at atmospheric pressure (AP-PECVD) are strongly emerging to address this issue. In a typical AP-PECVD controlled by dielectric barriers, inorganic or organometallic precursors (e.g., TiCl4, TiN, SiH4, Si2O(CH3)2) are introduced between two parallel electrodes along with a carrier gas (e.g., N2, Ar, He) at atmospheric pressure where, on interaction with plasma species, undergo fragmentation. The resulting fragments can react with the substrate or with each other to produce short-lived species required for coating deposition. The structural and functional features of PECVD coatings (e.g., surface roughness, biocompatibility, wetting and optical properties) depend on several deposition parameters, including the power dissipated in the discharge, type of plasma discharge, precursor concentration, and the flow rate of gases. With this in mind, the feasibility of conferring fogging resistance to commercial glass samples via AP-PECVD has been demonstrated in this doctoral thesis. By appropriately controlling the deposition parameters, anti-fogging coatings were prepared using 1,3,5,7- tetramethylcyclotetrasiloxane (Si4O4H4(CH3)4) and nitrous oxide (N2O) by a dielectric barrier discharge operated in N2 at atmospheric pressure (AP-DBD). When coating deposition was conducted in static conditions, that is, with no relative movement between the glass sample and the electrodes, quantitative assessment of the fogging resistance (ASTM F 659-06 standard) revealed that coatings obtained under [N2O]/[TMCTS] ratios ³ 30 or under a dissipated power ³ 0.25 W cm-2 endowed glass samples with the anti-fogging property (transmittance > 80%), because of their hydrophilic nature. In terms of the [N2O] + [TMCTS] sum, the amount of TMCTS and N2O injected into the discharge did not appear to have a great impact on the anti-fogging performance. Indeed, as no significant changes in surface roughness were observed (Rrms and Ra were between 3 and 6 nm), the origin of the anti-fogging performance was attributed to the surface chemistry. To this end, an arbitrary parameter, called “fogging ratio”, was defined considering FTIR results to account for, along with O/Si ratios (XPS results), the observed anti-fogging performance. Fogging ratios in the 0-0.10 range coupled with O/Si ratios ³ 2.3, resulting from the presence of hydrophilic functionalities, such as silanol (Si-OH), hydroxyl (C-OH) carboxyl (COOH), and ester (COOR) groups at the coating surface were necessary to attain the anti-fogging property. Interestingly, coatings prepared in dynamic conditions using three other precursors with different structures and different number of Si-H and Si-CH3 groups; namely, octamethylcyclotetrasiloxane (OMCTS), 1,1,3,3-tetramethyldisiloxane (TMDSO), and hexamethyldisiloxane (HMDSO) were not fogging-resistant. This result leads us to believe that the cyclic structure of TMCTS in conjunction with the high reactivity of Si-H bonds is behind the formation of the above-mentioned hydrophilic functionalities, and thus the antifogging performance of TMCTS-coated glasses

Heat Transfer

Over the past few decades there has been a prolific increase in research and development in area of heat transfer, heat exchangers and their associated technologies. This book is a collection of current research in the above mentioned areas and describes modelling, numerical methods, simulation and information technology with modern ideas and methods to analyse and enhance heat transfer for single and multiphase systems. The topics considered include various basic concepts of heat transfer, the fundamental modes of heat transfer (namely conduction, convection and radiation), thermophysical properties, computational methodologies, control, stabilization and optimization problems, condensation, boiling and freezing, with many real-world problems and important modern applications. The book is divided in four sections : "Inverse, Stabilization and Optimization Problems", "Numerical Methods and Calculations", "Heat Transfer in Mini/Micro Systems", "Energy Transfer and Solid Materials", and each section discusses various issues, methods and applications in accordance with the subjects. The combination of fundamental approach with many important practical applications of current interest will make this book of interest to researchers, scientists, engineers and graduate students in many disciplines, who make use of mathematical modelling, inverse problems, implementation of recently developed numerical methods in this multidisciplinary field as well as to experimental and theoretical researchers in the field of heat and mass transfer

Concept, implementation and analysis of the piezoelectric resonant sensor / Actuator for measuring the aging process of human skin

The main goal of the dissertation was following: preparation of a new concept, implementation and analysis of the piezoelectric resonant sensor/actuator for measuring the aging process of human skin. The research work has been carried out in the framework of cooperation between the INP-ENSEEIHT-LAPLACE, Toulouse, France, and at the Gdansk University of Technology, Faculty of Electrical and Control Engineering, Research Group of Power Electronics and Electrical Machines, Gdask, Poland. A concept of transducer for the characterization of mechanical properties of soft tissues was presented. The piezoelectric resonant, bending transducer, referred to as “unimorph transducer” was chosen from different topologies of piezoelectric benders based on the fulfillment of the stated requirements. The innovation of the project lies in the integration of the dynamic indentation method by using a unimorph as an indentation device. This allows the use of a number of attractive electromechanical properties of piezoelectric transducers. The thesis is divided into seven chapters. Chapter 1 states the thesis and goals of the dissertation. Chapter 2 presents piezoelectric phenomenon and piezoelectric applications in the fields of medicine and bioengineering. Chapter 3 describes the requirements for the developed transducer. The choice of unimorph transducer is justified. Chapter 4 presents an analytical description of the unimorph transducer, including the calculations of static deformations, equivalent circuit description, and description of the contact conditions between the transducer and the tested materials. Chapter 5 contains the numerical analysis of the unimorph transducer using FEM virtual model. Results of static and modal simulations are described for two considered geometries of the transducer. Chapter 6 describes the experimental verification process of analytic and numerical models developed for unimorph transducer. The final chapter includes general conclusions concerning obtained research results and achievements, as well as possible future works. In order to verify the proposition of the thesis a full research cycle was carried out, that covered: analytical study, numerical analysis (FEM simulations), prototype realization, and experimental verification of the considered (developed) piezoelectric sensor/actuator structures