Mechanical Engineering

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Shiv Nadar University

Micro/nano scale surface modifications of titanium based orthopedic and cardiovascular implants has shown to augment biocompatibility. However, bacterial infection remains a serious concern for implant failure, aggravated by increasing antibiotic resistance and over usage of antibiotics. Bacteria cell adhesion on implant surface leads to colonization and biofilm formation resulting in morbidity and mortality. Hence, there is a need to develop new implant surfaces with high antibacterial properties. Recent developments have shown that superhydrophobic surfaces prevent protein and bacteria cell adhesion. In this study, a thermochemical treatment was used modify the surface properties for high efficacy antibacterial activity on titanium surface. The modification led to a micro-nano surface topography and upon modification with polyethylene glycol (PEG) and silane the surfaces were superhydrophilic and superhydrophobic, respectively. The modified surfaces were characterized for morphology, wettability, chemistry, corrosion resistance and surface charge. The antibacterial capability was characterized with Staphylococcus aureus and Escherichia coli by evaluating the bacteria cell inhibition, adhesion kinetics, and biofilm formation. The results indicated that the superhydrophobic micro-nano structured titanium surface reduced bacteria cell adhesion significantly (>90%) and prevented biofilm formation compared to the unmodified titanium surface after 24 h of incubation. © 2022 Wiley Periodicals LLC.

World University root node

(SoE) School of Engineering

Journal of Biomedical Materials Research - Part A

Enhanced antibacterial properties on superhydrophobic micro-nano structured titanium surface

Antimicrobial coatings on metallic surfaces are rapidly emerging to combat bacterial pathogens. The excess use of conventional antibiotics increases the number of resistant strains at an alarming rate, which in turn leads to detrimental implications in the healthcare sector. Hence, it is of great importance in developing a new class of material with inherent bactericidal activity and good biocompatibility. In the present study, we have modified the aluminium surfaces by a coating of graphene oxide (GO) due to its excellent physicochemical properties, water dispersity and low cytotoxicity. Coatings were developed through facile and enviornment-friendly transfer method. The antimicrobial properties of GO coated aluminium are investigated against Gram-negative strain E. coli through agar plate counting and ‘Live/Dead’ fluorescence staining. Further, to shed light into the mechanism of antibacterial activity of GO at the molecular level, we have performed X-ray reflectivity (XRR) study considering a phospholipid multilayer as a model system to mimic bacteria cell membrane. Results show a significant bactericidal activity of the GO coatings compared to uncoated aluminium with lower concentration showing slightly better antibacterial property due to higher roughness. The obtained results may pave the way for engineering graphene-based antimicrobial coatings on a material surface using an easy, environment-friendly, cost-effective and straight forward processing route. © 2022 The Author(s)

Physics

(SoNS) School of Natural Sciences

Environmental Technology and Innovation

Graphene oxide coated aluminium as an efficient antibacterial surface

It is a difficult task for an assembly line manager to select an appropriate worker from the available workers' list to assign to an assembly line workstation. Since each available worker has a unique set of skills and abilities, this research considers the worker differences in their work performance. The worker's work performance is considered based on their working speed or productivity. Task execution time (TET) is the measure used to distinguish the worker's work performance. The TET prediction is made by the application of a knowledge-based system framework. Workers' historical work-time data is used to model the knowledge objects. Workers are classified as skilled and semi-skilled respective methodologies are given for both categories of workers. Statistical-based learning algorithms are proposed for skilled workers based on the worker's age, gender, and work skill. Similarly, worker's learning patterns are used for semi-skilled workers. The predicted TET is used in solving the assembly line worker assignment problem. The second part of this work is to prioritise the aged worker during the worker selection without increment of worker count. The illustrative example helps understand the scope of the proposed methodology in an assembly line worker assignment problem. © 2022 Elsevier B.V.

International Journal of Production Economics

Modelling and prediction of worker task performance using a knowledge-based system application

The stepwise hydration of clay minerals has been observed repeatedly in studies, but the underlying mechanism remains unclear. Previous numerical studies confirmed the presence of one-water layer (1W) and two-water layer (2W) hydration states. However, the undisturbed transition between these hydration states has never been captured. Using molecular dynamics simulation, this study (i) simulated for the first time the free 1W–2W transition during clay hydration and (ii) identified the underlying mechanism to be the detachment of cations from the clay surface and the formation of a shell of water molecules around the cation. The swelling dynamics of clay was found to be affected by the clay charge, clay mineralogy, and counterions through complex cation–clay interactions, cation hydration capacity, and cation migration rate. © 2022 The Authors. Published by American Chemical Society

ACS Omega

Clay Swelling: Role of Cations in Stabilizing/Destabilizing Mechanisms

Procedia CIRP

<p>A dynamic job rotation scheduling conceptual framework by a human representing digital twin</p>

Journal of Stored Products Research

Enviro-economical feasibility of groundnut drying under greenhouse and indoor forced convection hot air dryers

The present study aims to investigate the synchronization characteristics of a pitch–plunge aeroelastic system subjected to coupled structural free-play and dynamic stall-induced aerodynamic nonlinearities. The semi-empirical Leishman–Beddoes (LB) aerodynamic model is used to capture the dynamic stall phenomena at large angles-of-attack (AoA). A bifurcation analysis, considering the flow-speed as the control parameter, reveals that the free-play nonlinearity is primarily responsible for the dynamical transition in the presence of the attached flow. In this case, a pitch and plunge frequency coalescence takes place through an aperiodic to periodic signature transition. Furthermore, by tracking the flow specific variables estimated using the LB model, it is observed that the onset of the dynamic stall plays a pivotal role in the bifurcation scenario at high flow speed regimes, marking the presence of stall flutter. The framework of synchronization is used to discern the response dynamics at low speed and high speed flow regime by estimating the pitch and plunge modal frequencies and their corresponding phase components. The routes to synchronization are identified to be through phase-locking (frequency coalescence) and through suppression of the plunge mode by the dominance of pitching frequency in the regimes before and after the onset of dynamic stall, respectively. Finally, it is shown that the different synchronization routes can possibly be a useful tool to identify the presence of stall flutter oscillations in a coupled aeroelastic system. © 2021

International Journal of Non-Linear Mechanics

Routes to Synchronization in a pitch–plunge aeroelastic system with coupled structural and aerodynamic nonlinearities

A novel cutting strategy of machining microstructure surface with the multi-tip diamond tool based on the force modulation approach is proposed in this paper. The multi-tip diamond tool with periodic sinusoidal microstructures was prepared by focused ion beam technique. The influence of applied cutting forces on the depths of cut and material removal states was investigated experimentally. MD simulations revealed a significant phenomenon of no material side flow when using the multi-tip diamond tool cutting on single crystal copper substrate. The movement of stacking faults, Lomer-Cottrell locks and Hirth locks jointly governed the formation mechanism of machined surface. To demonstrate the feasibility and effectiveness of this proposed cutting strategy, the fabrication of periodic sinusoidal microstructures under constant forces was successfully realized on the microsphere surface. Furthermore, three-dimensional sin-shaped ripples required variable forces controlling were achieved with high-precision surface quality. The cross-sectional topography of obtained ripples matched the geometry of used MTD tool quite well. In particular, the processing parameters, including the time period of loading forces and cutting speeds, determine the expected wavelength of ripples and play a central role in the surface machining accuracy. © 2021 The Society of Manufacturing Engineers

Journal of Manufacturing Processes

Fabrication of three-dimensional sin-shaped ripples using a multi-tip diamond tool based on the force modulation approach

The current work talks about a stochastic approach to study the static response characteristics of natural fiber reinforced composites with random material and geometric properties. Stochasticity in macro scale is due to randomness in macro mechanical properties of bio composite which is inevitable owing to many uncontrollable parameters in manufacturing and fabrication processes of bio composites. Analysis is also done by taking ply orientation angles (meso scale) and other geometric properties like aspect ratio, thickness ratio as discrete random variables. Bio composite is made of sisal fiber(Natural fiber) and matrix based on Epoxidized Soybean-Oil(ESO). Macro-mechanical analysis of composite laminates is done using Finite element analysis and first order shear deformation theory (FSDT) is used for displacement formulation. Results are shown for different boundary conditions along with different stacking sequences and thickness ratios. Uncertainty quantification is done using Monte Carlo simulation technique by considering the mean and the standard deviation of input material properties of the bio composite to be known. Sensitivity analysis is done to show how each stochastic input parameter (Elastic modulii) influence thecomposite plate response characteristics. The validation of the modelis checked using the existing results which are in agreement with the results obtained. Results indicate that stochasticity in material or geometric properties of bio composite cannot be ignored. It is concluded that considering stochasticity of input parameters in design and analysis of structures is crucial to maintain structural integrity, safety and reliability. © 2021 Author(s).

AIP Conference Proceedings

Stochastic analysis of natural fiber-reinforced composites

The effect of microwave processing on the high temperature oxidation behavior of AlCrTiTaMo equimolar composition was investigated. The long term oxidation studies were carried out at 900 °C and 1100 °C for 100 h. Oxidation kinetics of the microwave-processed alloy yields a significant decrease in the oxidation rate and mass gain compared to the as-cast alloy. The physical nature and stability of thermally formed oxide on the as-cast and processed samples were probed using long-term electrochemical impedance spectroscopy (EIS) studies. The impedance of the oxide formed on the as-cast alloy decreased with the immersion time while it continuously increased for the microwave processed alloy suggesting its stable and defect free nature. The superior oxidation behavior of microwave-processed alloy was attributed to microstructural homogenization leading to the formation of protective oxide layer with favorable chemistry and structure. © 2021 Elsevier B.V.