Micro/Nano-Chip Electrokinetics

Micro/nanofluidic chips have found increasing applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics has become the method of choice in these micro/nano-chips for transporting, manipulating and sensing ions, (bio)molecules, fluids and (bio)particles, etc., due to the high maneuverability, scalability, sensitivity, and integrability. The involved phenomena, which cover electroosmosis, electrophoresis, dielectrophoresis, electrohydrodynamics, electrothermal flow, diffusioosmosis, diffusiophoresis, streaming potential, current, etc., arise from either the inherent or the induced surface charge on the solid-liquid interface under DC and/or AC electric fields. To review the state-of-the-art of micro/nanochip electrokinetics, we welcome, in this Special Issue of Micromachines, all original research or review articles on the fundamentals and applications of the variety of electrokinetic phenomena in both microfluidic and nanofluidic devices

Development of a high power density combustion system for a silicon micro gas turbine engine

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000."February 2000."Includes bibliographical references (p. 203-211).As part of an effort to develop a microfabricated gas turbine engine capable of providing 10-50 Watts of electrical power in a package less than one cubic centimeter in volume, this thesis presents the design, fabrication, packaging and testing of the first combustion system for a silicon micro heat engine. The design and operation of a microcombustor is fundamentally limited by the chemical reaction times of the fuel, by silicon material and fabrication constraints, and by the inherently non-adiabatic nature of the operating space. This differs from the design of a modern macro combustion system that is typically driven by emissions, stability, durability and pattern factor requirements. The combustor developed herein is shown to operate at a power density level that is at least an order of magnitude higher than that of any other power-MEMS device (2000 MW/m 3), and establishes the viability of using high power density, silicon-based combustion systems for heat engine applications at the micro-scale. This thesis presents the development of two specific devices - the first device is a 3-wafer level microcombustor that established the viability of non-premixed hydrogen-air combustion in a volume as small as 0.066 cm 3, and within the structural constraints of silicon; the second device is known as the engine "static-structure", and integrated the 3-stack microcombustor with the other non-rotating components of the engine. Fabricated by aligned fusion bonding of 6 silicon wafers, the static structure measures 2.1 cm x 2.1 cm x 0.38 cm, and was largely fabricated by deep reactive ion etching through a total thickness of 3,800 pm. Packaged with a set of fuel plenums, pressure ports, fuel injectors, igniters, fluidic interconnects, and compressor and turbine static airfoils, this structure is the first demonstration of the complete hot flow path of a multi-level microengine. The 0.195 cm 3 combustion chamber has been tested for several tens of hours and is shown to sustain stable hydrogen combustion with exit gas temperatures above 1600K and combustor efficiencies as high as 95%. The structure also serves as the first experimental demonstration of hydrocarbon microcombustion with power density levels of 500 MW/m 3 and 140 MW/m 3 for ethylene-air and propane-air combustion, respectively. In addition to the development of the two combustion devices, this thesis also presents simple analytical models to identify and explain the primary drivers of combustion phenomena at the micro-scale. The chemical efficiency of the combustor is shown to have a strong correlation with the Damkohler number in the chamber, and asymptotes to unity for sufficiently large values of Da. The maximum power density of the combustor is also shown to be primarily limited by the structural and fabrication constraints of the material. Overall, this thesis synthesizes experimental and computational results to propose a simple design methodology for microcombustion devices, and to present design recommendations for future microcombustor development. Combined with parallel efforts to develop thin-film igniters and temperature sensors for the engine, it serves as the first experimental demonstration of the design, fabrication, packaging and operation of a silicon-based combustion system for power generation applications at the micro-scale.by Amitav Mehra.Ph.D

Electroanalytical point-of-care detection of gold standard and emerging cardiac biomarkers for stratification and monitoring in intensive care medicine - a review

Determination of specific cardiac biomarkers (CBs) during the diagnosis and management of adverse cardiovascular events such as acute myocardial infarction (AMI) has become commonplace in emergency department (ED), cardiology and many other ward settings. Cardiac troponins (cTnT and cTnI) and natriuretic peptides (BNP and NT-pro-BNP) are the preferred biomarkers in clinical practice for the diagnostic workup of AMI, acute coronary syndrome (ACS) and other types of myocardial ischaemia and heart failure (HF), while the roles and possible clinical applications of several other potential biomarkers continue to be evaluated and are the subject of several comprehensive reviews. The requirement for rapid, repeated testing of a small number of CBs in ED and cardiology patients has led to the development of point-of-care (PoC) technology to circumvent the need for remote and lengthy testing procedures in the hospital pathology laboratories. Electroanalytical sensing platforms have the potential to meet these requirements. This review aims firstly to reflect on the potential benefits of rapid CB testing in critically ill patients, a very distinct cohort of patients with deranged baseline levels of CBs. We summarise their source and clinical relevance and are the first to report the required analytical ranges for such technology to be of value in this patient cohort. Secondly, we review the current electrochemical approaches, including its sub-variants such as photoelectrochemical and electrochemiluminescence, for the determination of important CBs highlighting the various strategies used, namely the use of micro- and nanomaterials, to maximise the sensitivities and selectivities of such approaches. Finally, we consider the challenges that must be overcome to allow for the commercialisation of this technology and transition into intensive care medicine. Graphical abstract: [Figure not available: see fulltext.

Mathematical modelling of fluid flows in textured and autophoretic microchannels

Further advancement in the field of microfluidics relies on the improved understanding and exploitation of fluid phenomena at the micro-scale. Such phenomena may influence the design of microfluidic devices, to achieve desirable effects in the fluid. This thesis specifically concerns itself with superhydrophobic drag reduction and self-diffusiophoretic (autophoretic) motion. The former can be achieved in practice by texturing microchannel boundaries with grooves parallel to the flow direction. Such grooves contain an inert gas and/or vapor, the low viscosity of which results in apparent slip flow in the liquid phase. With applications of textured microchannels including direct liquid cooling of microelectronics, there is a need for predictive mathematical models that can be used for design and optimization. This thesis is comprised of the motivation, development and discussion of such models, including analysis and numerical computations. In the context of textured channels, we study the effects of gas viscosity (interfacial shear), meniscus protrusion, channel aspect ratio, thermal transport and slowly varying three-dimensional geometry and show how to generate accurate predictions using Chebyshev collocation and domain decomposition numerical methods. In addition, we use the same numerical formulation to study autophoretic (self-diffusiophoretic) channels, in the presence of advection. Such channels rely on a chemical interaction between its boundaries and a solute (e.g. adsorption, repulsion) to generate an effective slip velocity at the solid-liquid interface proportional to the concentration gradient. We study the general case of corrugated boundaries, showing how advection can lead to flow enhancement, or flow reversal. We also study channels with flat boundaries, and demonstrate that advection can lead to the spontaneous emergence of non-trivial flow fields.Open Acces

Optimization of a micromechanical single element oscillator using nonlinear electrostatic cotnrol

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1998.Includes bibliographical references (p. 269-271).by Jonathan Andrew Kossuth.Ph.D

Flowing matter

This open access book, published in the Soft and Biological Matter series, presents an introduction to selected research topics in the broad field of flowing matter, including the dynamics of fluids with a complex internal structure -from nematic fluids to soft glasses- as well as active matter and turbulent phenomena.Flowing matter is a subject at the crossroads between physics, mathematics, chemistry, engineering, biology and earth sciences, and relies on a multidisciplinary approach to describe the emergence of the macroscopic behaviours in a system from the coordinated dynamics of its microscopic constituents.Depending on the microscopic interactions, an assembly of molecules or of mesoscopic particles can flow like a simple Newtonian fluid, deform elastically like a solid or behave in a complex manner. When the internal constituents are active, as for biological entities, one generally observes complex large-scale collective motions. Phenomenology is further complicated by the invariable tendency of fluids to display chaos at the large scales or when stirred strongly enough. This volume presents several research topics that address these phenomena encompassing the traditional micro-, meso-, and macro-scales descriptions, and contributes to our understanding of the fundamentals of flowing matter.This book is the legacy of the COST Action MP1305 “Flowing Matter”

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators

Aeronautical enginnering: A cumulative index to a continuing bibliography (supplement 312)

This is a cumulative index to the abstracts contained in NASA SP-7037 (301) through NASA SP-7073 (311) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled by the Center for AeroSpace Information of the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract number, report number, and accession number indexes