Papers by Author: M. Rizwan Malik

Abstract: Multiphysics numerical simulation (MPNS) has certainly acquired a wide acceptance in the modeling, designing and fabrication fields and has been validated for various research applications. But it is important that the method should be thoroughly understood by students of the various fields. Keeping this aim in view, we demonstrate here the MPNS process as applied in several fields, such as: electrostatics, mechanics, chemistry, heat transfer and fluid flow. Four tasks are performed for fifteen hours in order to analyze simulation approaches such as modeling with geometrical parameters, meshing, solution and post-processing methods. Convection, buoyancy effects, microfiltration and flow analysis are investigated. This comprehensive study will enhance appreciation of the basic concepts of design and dimensioning of an object in MEMS for engineers, and help to guide workers in these fields when performing these tasks.

Abstract: A growing scientific effort is being devoted to the study of nanoscale interface aspects such as thin-film adhesion, abrasive wear and nanofriction at surfaces by using the nanoscratching technique but there remain immense challenges. In this paper, a three-dimensional (3D) model is suggested for the molecular dynamics (MD) simulation and experimental verification of nanoscratching initiated from nano-indentation, carried out using atomic force microscope (AFM) indenters on Al-film/Si-substrate systems. Hybrid potentials such as Morse and Tersoff, and embedded atom methods (EAM) are taken into account together for the first time in this MD simulation (for three scratching conditions: e.g. orientation, depth and speed, and the relationship between forces and related parameters) in order to determine the mechanisms of nanoscratching phenomena. Salient features such as nanoscratching velocity, direction and depth - as well as indenter shape- and size-dependent functions such as scratch hardness, wear and coefficient of friction - are also examined. A remarkable conclusion is that the coefficient of friction clearly depends upon the tool rake-angle and therefore increases sharply for a large negative angle.

Abstract: Much of the recent ongoing advanced research into the quest for improved etching techniques has brought forth a broad concept for the fabrication of micro/nano-electromechanical systems (MEMS/NEMS) having high accuracy, precision, efficiency, compatibility and through-put of metallic- as well as carbon-composition structural phases. This in turn leads towards a thorough understanding of the sensing, trapping, separating, controlling, positioning, directing, concentrating and manipulating of micro-nano-sized particles - predominantly biological particles - in the emerging MEMS/NEMS technological field. This paper focuses its attention on the easiest means of wet-etching {100}-type silicon wafer surfaces by guiding the choice of [<100> or <010>] orientation (at 45° to the normal orientation). This anisotropic etching is performed in KOH solution. Here, consideration is not concerned to a large extent with process parameters as in anodic oxidation, an intensely doped boron etching stops and silicon wafer surface back-etching. The main concern of the present practical application route involves a passivating material (silicon dioxide, SiO2) and two masking stages (for a two-step etching process). As a example of this method, silicon cantilever beams having vertical edges are produced. It is concluded that the method presented will be helpful in the comprehensive study of resonators, pressure/temperature sensors, three-dimensional carbon micro-electrodes, actuators and accelerometers for bioparticle applications.

Abstract: A dielectrophoretic approach with latest developed three-dimensional (3-D) carbon micro-electro-mechanical system (C-MEMS) has been extended as a potential route with idyllic solution to recommend a low-cost, biocompatible and high throughput manipulation and positioning for bio-particles as compared to 2D-planar microelectrodes. Presented in this paper is a novel platform for modelling and simulation of C-MEMS microfabrication process for dielectrophoresis (DEP) force based on various 3-D offset-microelectrode configurations. Numerical solutions are employed to investigate the upshots of multi-designed microelectrodes, applied voltage, electrode edge-to-edge gap and geometric size of microelectrodes on the electric field intensity gradient, induced by an AC voltage for the deployment of broad categories of bioparticles creation, utilization and their manipulation (separation, concentration, transportation and focusing). Sharp edge electrodes are the principle focus of this paper for DEP manipulation that is more convenient to enhance the electric field intensity distribution. The results show that square column electrodes configuration comparatively create large gradient magnitude in electric field intensity as compared to all other configurations. It is also observed that electric field extends drastically with increases in microelectrode height. These findings are consistent with literature experimental reports and will provide vital strategy for optimal design of DEP devices with 3-D C-MEMS.

Abstract: It is critical to understand multiphase flow applications with regard to dynamic behavior. In this paper, a systematic approach to the study of these applications is pursued, leading to separated flows comprising the effects of free surface flows and wetting. For the first time, wetting phenomena (three wetting regimes such as no wetting, 90 ^º wetting angle and absolute wetting) are added in the separated flow model. Special attention is paid to computational fluid dynamics (CFD) in order to envisage the relationship between complex metallurgical practices such as mass and momentum exchange, turbulence, heat, reaction kinetics and electromagnetic fields. Simulations are performed in order to develop sub-models for studying multiphase flow phenomena at larger scales. The outcomes show that a proper mixture of techniques is valuable for constructing larger-scale models based upon sub-models for recreating the hierarchical structure of a detailed CFD model applicable throughout the process.