Surface Properties of Nanopore-Structured Metals and Oxides

The importance of understanding the properties of textured surfaces is growing with their potential wide engineering applications. In this thesis research, nanopore structures of metals and oxides were examined to determine the interactions between environmental object and the textured surfaces. The major applications of nanopore structures are micro/nanoelectromechanical systems (MEMS/NEMS), energy devices, sensors, and environmental devices. In order to achieve better performance in each, it needs to consider three critical surface properties such as surface forces, electrochemical performances, and wettability. In this research, the surface properties of nanopore structures have been explored with understanding the essence of contact. This research uses experimental approach combined with basic analysis in physical principles. Experiments include fabrication of nanopore structures, investigation of surface force, electrochemical evaluation, and wetting/electrowetting studies of nanopore structures. Metallic nanopore structures (MNSs) of nickel were characterized by using an atomic force microscope (AFM) and a triboscope. The mechanisms of bacteria desorption were examined by alumina nanopore structures (ANSs) with various pore sizes. The kinetics of ion-transfer on MNSs was studied using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltametry (CV). The (electro-) wetting behavior of MNSs were examined using a droplet shape measurement system. A physics based analysis was conducted in order to understand the principles of the nanopore effects on environments suitable for various applications. Results lead to the successful identification of critical geometrical factors. A contact model has been established to understand properties of textured surfaces. Specific design factors, which are related to the geometry of the textured surfaces has been identified. This research revealed fundamental mechanisms of contact and establish a relationship between morphology/geometry and surface properties. The findings in this thesis research afford new approach to optimize applications of textured surface. The proposed contact models are beneficial to the surface design and application of sustainable micro/nanodevices. This thesis includes eight chapters. The first chapter introduces the background and fundamental knowledge related to current research in order to understand the basics. Followed by the chapter two of motivation and objectives, chapter three discusses materials and experimental details, chapter four and five cover the surface forces, chapter six studies the electrochemical performances, chapter seven investigates the (electro-)wettability, and the conclusions and future recommendations are presented in chapter eight

Surface Properties of Nanopore-Structured Metals and Oxides

The importance of understanding the properties of textured surfaces is growing with their potential wide engineering applications. In this thesis research, nanopore structures of metals and oxides were examined to determine the interactions between environmental object and the textured surfaces. The major applications of nanopore structures are micro/nanoelectromechanical systems (MEMS/NEMS), energy devices, sensors, and environmental devices. In order to achieve better performance in each, it needs to consider three critical surface properties such as surface forces, electrochemical performances, and wettability. In this research, the surface properties of nanopore structures have been explored with understanding the essence of contact. This research uses experimental approach combined with basic analysis in physical principles. Experiments include fabrication of nanopore structures, investigation of surface force, electrochemical evaluation, and wetting/electrowetting studies of nanopore structures. Metallic nanopore structures (MNSs) of nickel were characterized by using an atomic force microscope (AFM) and a triboscope. The mechanisms of bacteria desorption were examined by alumina nanopore structures (ANSs) with various pore sizes. The kinetics of ion-transfer on MNSs was studied using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltametry (CV). The (electro-) wetting behavior of MNSs were examined using a droplet shape measurement system. A physics based analysis was conducted in order to understand the principles of the nanopore effects on environments suitable for various applications. Results lead to the successful identification of critical geometrical factors. A contact model has been established to understand properties of textured surfaces. Specific design factors, which are related to the geometry of the textured surfaces has been identified. This research revealed fundamental mechanisms of contact and establish a relationship between morphology/geometry and surface properties. The findings in this thesis research afford new approach to optimize applications of textured surface. The proposed contact models are beneficial to the surface design and application of sustainable micro/nanodevices. This thesis includes eight chapters. The first chapter introduces the background and fundamental knowledge related to current research in order to understand the basics. Followed by the chapter two of motivation and objectives, chapter three discusses materials and experimental details, chapter four and five cover the surface forces, chapter six studies the electrochemical performances, chapter seven investigates the (electro-)wettability, and the conclusions and future recommendations are presented in chapter eight

LBM, a useful tool for mesoscale modelling of single phase and multiphase flow – the variety of applications and approaches at Nottingham

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Giving an overview of Nottingham group’s recent progress on numerical modelling and approaches in developing and applying the lattice Boltzmann method (LBM), the paper tries to demonstrate that the LBM is a useful tool for mesoscale modelling of single phase and multiphase flow. The variety of applications of the LBM modelling is reported, which include single phase fluid flow and heat transfer around or across rotational cylinder of curved boundary, two-phase flow in mixing layer, electroosmotically driven flow in thin liquid layer, bubbles/drops flow and coalescence in conventional channels and in microchannels with confined boundary, liquid droplets in gas with relative large density ratio; viscous fingering phenomena of immiscible fluids displacement, and flow in porous media

Carbon fibre composites: integrated electrochemical sensors for wound management

The applicability of employing a carbon fibre mesh as an electrochemical sensing substructure for assessing urate transformations within wound exudates is evaluated. Prototype sensor assemblies have been designed and their response characteristics towards uric acid and other common physiological components are detailed. Modification of the carbon fibre sensor through surface anodisation and the application of cellulose acetate permselective barriers have been shown to lead to optimized responses and much greater sensitivity (1440% increase) and specificity. These could enable the accurate periodic monitoring of uric acid in wound fluid. The performance characteristics of the composite sensors in whole blood, serum and blister fluid have been investigated

Current approaches for modulation of the nanoscale interface in the regulation of cell behavior

Regulation of cell behavior in response to nanoscale features has been the focus of much research in recent years and the successful generation of nanoscale features capable of mimicking the natural nanoscale interface has been of great interest in the field of biomaterials research. In this review, we discuss relevant nanofabrication techniques and how they are combined with bioengineering applications to mimic the natural extracellular matrix (ECM) and create valuable nanoscale interfaces

Design and Simulation of an Electrostatically-Driven MEMS Micro-Mixer

Bio MEMS ( Biology Micro-electro-mechanical Systems) focus on some micro-fabricated devices including electrical and mechanical parts to study the biological system such as new polymer-based drug delivery systems for anti-cancer agents, specialized tools for minimally invasive surgery, novel cell sorting systems for high-throughput data collection, and precision measurement techniques enabled by micro-fabricated devices. Especially some micro-liquid handling devices like micro-pumps, active and passive micro-mixers that can make two or more micro-fluids mixing completely, with the chaotic advection. This kind of rapid mixing is very important in the biochemistry analysis, drug delivery and sequencing or synthesis of nucleic acids. Besides, some biological processes like cell activation, enzyme reactions and protein folding also require mixing of reactants for initiation, electrophoresis activation. Turbulence and inter-diffusion of them play crucial role in the process of mixing of different fluids. In this report, it will introduce a new kind of electromechanical active micro-mixer, which includes two inlets and one outlet under the electrostatic driven voltage. Two different fluids will enter the micro-mixer and shows different colors separately blue and red. Choosing the ANSYS for the simulation of the fluids running in the micro-mixers, we can see nearly 100% fluids that have been mixed. ANSYS is used to show the effectiveness of the micro-mixer

Adhesion modulation In bio-inspired micropatterned adhesives by electrical fields

With steps towards Industry 4.0, it becomes imperative to the development of next-generation industrial assembly lines, to be able to modulate adhesion dynamically for handling complex and diverse substrates. The inspiration for the design and functionality of such adhesive pads comes from gecko’s remarkable ability to traverse rough and smooth topographies with great ease and agility. The emphasis in this thesis was to equip artificial micropatterned adhesives with such functionalities of tunability and devise an on-demand release mechanism. The project evaluates the potential of electric fields in this direction. The first part of this work focusses on integrating electric fields with polymeric micropatterns and studying the synergistic effect of Van der Waals and electrostatic forces. An in-house electroadhesion set up was built to measure the pull-off forces with and without electric fields. As a function of the applied voltage, adhesion forces can be tuned. The second part of the work demonstrates a novel route that exploits the in-plane actuation of the dielectric elastomeric actuators integrated with microstructure to induce peeling in them. Voltage-dependent actuation has been harnessed to generate the requisite peel force to detach the micropatterns. Overall, the findings of this thesis combine disciplines of electroadhesion, electroactuation, and reversible dry adhesives to gain dynamic control over adhesion.Im Einklang mit dem Fortschreiten in Richtung Industrie 4.0, wird es auch für die Entwicklung von industriellen Montagelinien der nächsten Generation unerlässlich sein, die Handhabung komplexer und unterschiedlicher Objekte zu flexibilisieren. Bioinspirierte Haftpads nach dem Vorbild des Gecko könnten zukünftig hierzu wesentlich beitragen. Der Schwerpunkt dieser Arbeit bestand darin, künstliche mikrostrukturierte Haftpads mit einem elektrisch schaltbaren Adhäsions- und Ablösemechanismus zu funktionalisieren, um die Grundlage für einen schnell schaltbaren, intelligenten Greifer zu schaffen. Der erste Teil dieser Arbeit konzentriert sich auf die Kombination elektrischer Felder mit elastomeren Mikrostrukturen und die Untersuchung der synergistischen Wirkung von Van der Waals- und elektrostatischen Kräften. Zur Messung der Adhäsion wurde ein individueller Aufbau realisiert und mit diesem die Feldstärkeabhängigkeit der Haftkräfte nachgewiesen. Der zweite Teil der Arbeit demonstriert einen neuartigen Ablösemechanismus unter Ausnutzung der lateralen Bewegung dielektrischer elastomerer Aktuatoren, um so ein Abschälen der Haftpads vom Substrat zu induzieren. Durch Variation der elektrischen Spannung wurde untersucht, wie sich diese auf die Ablösegeschwindigkeit der Haftpads auswirkt. Insgesamt kombinieren die Ergebnisse dieser Arbeit die Disziplinen Elektroadhäsion, Elektroaktuation und reversible trockene Klebstoffe, um so eine dynamische Kontrolle über die Adhäsion zu erhalten

Laser-based packaging of micro-devices

In this PhD thesis the development of laser-based processes for packaging applications in microsystems technologies is investigated. Packaging is one of the major challenges in the fabrication of micro-electro-mechanical systems (MEMS) and other micro-devices. A range of bonding processes have become established in industry, however, in many or even most cases heating of the entire package to the bonding temperature is required to effect efficient and reliable bonding. The high process temperatures of up to 1100°C involved severely limit the application areas of these techniques for packaging of temperature sensitive materials. As an alternative production method, two localised heating processes using a laser were developed where also the heat is restricted to the joining area only by active cooling. Silicon to glass joining with a Benzocyclobutene adhesive layer was demonstrated which is a typical MEMS application. In this laser-based process the temperature in the centre of the device was kept at least 120°C lower than in the bonding area. For chip-level packaging shear forces as high as 290 N were achieved which is comparable and some cases even higher than results obtained using conventional bonding techniques. Furthermore, a considerable reduction of the bonding time from typically 20 minutes down to 8 s was achieved. A further development of this process to wafer-level packaging was demonstrated. For a simplified pattern of 5 samples the same quality of the seal could be achieved as for chip-level packaging. Packaging of a more densely packed pattern of 9 was also investigated. Successful sealing of all nine samples on the same wafer was demonstrated proving the feasibility of wafer-level packaging using this localised heating bonding process. The development of full hermetic glass frit packaging processes of Leadless Chip Carrier (LCC) devices in both air and vacuum is presented. In these laser-based processes the temperature in the centre of the device was kept at least 230°C below the temperature in the joining region (375°C to 440°C). Testing according to MIL-STD-883G showed that hermetic seals were achieved in high yield processes (>90%) and the packages did withstand shear forces in excess of 1 kN. Residual gas analysis has shown that a moderate vacuum of around 5 mbar was achieved inside the vacuum packaged LCC devices. A localised heating glass frit packaging process was developed without any negative effect of the thermal management on the quality of the seal

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals