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An investigation is presented of the use of alternating current (AC) electrical treatment to induce the collapse of stable house-of-cards clay microstructures of oil sands tailings, producing aggregation and dewatering. Tailings samples, from Alberta, Canada, having solids contents of ca. 30 or 40 wt.%, similar clay types (kaolinite/illite) and different electrode load impedances are studied. At AC frequencies between 10 kHz and 1 MHz, application of an AC electric field between 500 and 1 400 V/m gives rise to a desirable type of uniform aggregation and dewatering effect. Tailings with ca. 30 wt.% initial solids content are transformed into ca. 40 and 55 wt.% solids content on loose and strong aggregation, respectively, and tailings with ca. 40 wt.% initial solids content are transformed into ca. 50 and 60 wt.% solids content, respectively. Gravity settling tests indicate that the dewatering effect from both loose and strong aggregates produces 12% maximum water recovery after 10 d. Freeze-dried scanning electron microscopy shows the transformation of tailings from an initial stable house-of-cards microstructure into densely packed aggregates following AC electrical treatment., An investigation is presented of the use of alternating current (AC) electrical treatment to induce the collapse of stable house-of-cards clay microstructures of oil sands tailings, producing aggregation and dewatering. Tailings samples, from Alberta, Canada, having solids contents of ca. 30 or 40 wt.%, similar clay types (kaolinite/illite) and different electrode load impedances are studied. At AC frequencies between 10 kHz and 1 MHz, application of an AC electric field between 500 and 1 400 V/m gives rise to a desirable type of uniform aggregation and dewatering effect. Tailings with ca. 30 wt.% initial solids content are transformed into ca. 40 and 55 wt.% solids content on loose and strong aggregation, respectively, and tailings with ca. 40 wt.% initial solids content are transformed into ca. 50 and 60 wt.% solids content, respectively. Gravity settling tests indicate that the dewatering effect from both loose and strong aggregates produces 12% maximum water recovery after 10 d. Freeze-dried scanning electron microscopy shows the transformation of tailings from an initial stable house-of-cards microstructure into densely packed aggregates following AC electrical treatment.

A micro differential thermal analysis (DTA) system is used for detection of trace explosive particles. The DTA system consists of two silicon micro chips with integrated heaters and temperature sensors. One chip is used for reference and one for the measurement sample. The sensor is constructed as a small silicon nitride membrane incorporating heater elements and a temperature measurement resistor. In this manuscript the DTA system is described and tested by measuring calorimetric response of 3 different kinds of explosives (TNT, RDX and PETN). This project is carried out under the framework of the Xsense project at the Technical University of Denmark (DTU) which combines four independent sensing techniques, these micro DNT sensors will be included in handheld explosives detectors with applications in homeland security and landmine clearance.

A heater design, used in a micro-calorimetric sensor, has been optimized for temperature uniformity and the sensor has been used for detection of trace amounts of explosives. In this abstract the design, characterization and functionality is described. The performance of the novel heater design is characterized by measuring the temperature coefficient of resistivity (TCR) values and by mapping the temperature distribution using Raman spectroscopy. The new heater design has increased the temperature uniformity and calorimetric measurements on DNT (2,4-Dinitrotoluene) show more reproducible and better defined signals.

When a liquid droplet experiences a temperature inhomogeneity along its bounding surface, a surface energy gradient is engendered, which when, in a continuous sense, exceeding a threshold, results in a convective flow dissipating the energy. If the associated temperature gradients are sustained by the interface between the liquid and a supporting substrate, the induced flow can result in the lateral motion of the droplet overcoming the viscosity and inertia. Recently, pico-liter adsorbed and applied droplets were shown experimentally to be transported, and divided by the decay of optically excited surface plasmons into phonons in a thin gold foil. The decaying events locally modify the temperature of the liquid-solid interface, establishing microscale thermal gradients of sufficient magnitude for the droplet to undergo thermocapillary flow. We present experimental evidence of such gradients resulting in local surface modification associated with the excitation of surface plasmons. We show theoretically that the observed effect is due to Marangoni forces, and computationally visualize the flow characteristics for the experimental parameters. As an application based on our results, we propose a method for an all-optical modulation of light by light mediated by the droplet oscillations. Furthermore, the results have important consequences for microfluidics, droplet actuation, and simultaneous surface plasmon resonance sensing and spectroscopy., QC 20110816

We present experimental results from an all-optical microfluidic platform that may be complimented by a thin film all-electrical network. Using these configurations we have studied the microfluidic convective flow systems of silicone oil, glycerol, and 1,3,5-trinitrotoluene on open surfaces through the production of surface tension gradients derived from thermal gradients. We show that sufficient localized thermal variation can be created utilizing surface plasmons and/or engaging individually addressable resistive thermal elements. Both studies manipulate fluids via Marangoni forces, each having their unique exploitable advantages. Surface plasmon excitation in metal foils are the driving engine of many physical-, chemical-, and bio-sensing applications. Incorporating, for the first time, the plasmon concept in microfluidics, our results thus demonstrate great potential for simultaneous fluid actuation and sensing. (c) 2006 Elsevier B.V. All rights reserved., QC 20111004. Conference: 7th International Conferene on Scanning Probe Microscopy, Sensors and Nanostructures. Cancun, MEXICO. JUN 05-08, 2005

Localized surface-tension-driven forces (microscale Marangoni effect) caused by a temperature inhomogeneity from the decay of optically excited surface plasmons into phonons have been engaged in the actuation of adsorbed and applied liquid on a thin metal film. Microfluidic operations of transport, separation, mixing, and sorting have been experimentally and theoretically demonstrated using this all-optical modulation scheme., QC 20110815

Conduction through an assembly of nanosized clusters coupled by tunneling barriers is of significant interest both for understanding the fundamental physics involved and for potential applications. In this study, we describe a technique for preparing relatively large (dimensions of a few 100 microns to a few mm in size) monolayer films consisting of 3 nm diameter Au clusters coated with mercaptododecanoic acid, using low molecular weight-polymers as coupling agents. Electrical measurements of the assembly show non-linear characteristics. Below a certain threshold voltage, the current does not vary with an increase in voltage. Above this threshold voltage, current increases with voltage and can be described by a power-law relationship with an exponent close to unity. These characteristics of the I-V curve are discussed with specific reference to theoretical studies on conduction through an array of capacitance-coupled metallic islands and previous experimental results in similar systems., Pres: Symposium, 27-29 Nov 2000, Boston, MA, pC1.2.1-C1.2.6. This article is from ADA395000 Materials Research Society Symposium Proceedings Volume 635. Anisotropic Nanoparticles - Synthesis, Characterization and Applications

We demonstrate that it is possible to deposit a wide range of magnetic features, using photoassisted selective area organometallic chemical vapor deposition. Large arrays of identical micron-scale Ni features were deposited on a Si(111) wafer by this method. Their magnetic properties were studied by alternating gradient force magnetometry as well as magnetic force microscopy. Our morphological and magnetic measurements show that the structures are spatially well defined, and the magnetic properties are related to the structural shapes of the features. This method can be adapted to the fabrication of smaller-scale magnetic and electronic devices. ©1996 American Institute of Physics.