Electrophoretic deposition of ferrite

The ability to integrate a material with a high permeability on chip, allows for magnetically coupled circuits and structures to be designed and incorporated along side CMOS circuitry. Devices ranging from A.C. transformers to magnetically driven MEMS structures can be designed and fabricated. Desirable characteristics of magnetic cores for integrated inductors and transformers are first high saturation flux in order to obtain high saturation current; high permeability to obtain high inductance; high resistivity to reduce eddy current loss at high frequencies and compatible deposition and patterning processes. High frequency magnetic materials are oxide based ceramics and are therefore difficult to evaporate, sputter, plate and selectively etched. ElectroPhoretic Deposition (EPD) is a method where insulating particles are imparted charge in a suspension and are made to deposit on an electrode by applying electric field. EPD has been extensively employed in depositing oxide based phosphors for display applications. In this study, ferrite particles have been prepared by grinding sintered toroids and deposited by EPD. The electrophoretic solution bath is composed of isopropyl alcohol with traces of Mg(N03)2 and La(N03)3 salts. Glycerol is added to the solution bath as a surfactant to promote increased substrate adhesion. The dissociation of magnesium nitrate in the solution bath charges the ferrite particles. An electric field of ~ 50-160 V/cm is applied with negative terminal connected to the wafer to be plated and aluminum electrode is used as the anode. The deposition process is found to be self limiting with the initial high elerophoretic current declining to 10% of its value in 10 minutes. The deposition rate and zeta potential measurements indicate a high particle velocity on the order 5.7x10-3 cm/s with an electric field of 160V/cm generated across the 2 cm electrode spacing. Pattern filling and conformal coverage in copper damascene planar microinductors has been investigated. A method to extracted permeability from S11 impedance analysis has been employed. It has been found that grinding process deteriorates magnetic response. With recent advances in magnetic particle technology for high frequency materials, these results enable unique hard and soft powder ferrite material to be selectively deposited in wide variety of CMOS and MEM’s based applications

Highly ordered tailored three-dimensional hierarchical nano/microporous gold–carbon architectures

The preparation and characterization of three-dimensional hierarchical architectures, consisting of monolithic nanoporous gold or silver films formed on highly ordered 3D microporous carbon supports, are described. The formation of these nano/microporous structures involves the electrodeposition or sputtering of metal alloys onto the lithographically patterned multi-layered microporous carbon, followed by preferential chemical dealloying of the less noble component. The resulting hierarchical structure displays a highly developed 3D interconnected network of micropores with a nanoporous metal coating. Tailoring the nanoporosity of the metal films and the diameter of the large micropores has been accomplished by systematically changing the alloy compositions via control of the deposition potential, plating solution and coarsening time. SEM imaging illustrates the formation of unique biomimetic nanocoral- or nanocauliflower-like self-supporting structures, depending on the specific preparation conditions. The new 3D hierarchical nano/microporous architectures allow for enhanced mass transport and catalytic activity compared to common nanoporous films prepared on planar substrates. The functionality of this new carbon–gold hierarchical structure is illustrated for the greatly enhanced performance of enzymatic biofuel cells where a substantially higher power output is observed compared to the bare microporous carbon substrate

Remotely Interrogated Passive Polarizing Dosimeter (RIPPeD).

Conductive polymers have become an extremely useful class of materials for many optical applications. We have developed an electrochemical growth method for depositing highly conductive ({approx}100 S/cm) polypyrrole. Additionally, we have adapted advanced fabrication methods for use with the polypyrrole resulting in gratings with submicron features. This conductive polymer micro-wire grid provides an optical polarizer with unique properties. When the polymer is exposed to ionizing radiation, its conductivity is affected and the polarization properties of the device, specifically the extinction ratio, change in a corresponding manner. This change in polarization properties can be determined by optically interrogating the device, possibly from a remote location. The result is a passive radiation-sensitive sensor with very low optical visibility. The ability to interrogate the device from a safe standoff distance provides a device useful in potentially dangerous environments. Also, the passive nature of the device make it applicable in applications where external power is not available. We will review the polymer deposition, fabrication methods and device design and modeling. The characterization of the polymer's sensitivity to ionizing radiation and optical testing of infrared polarizers before and after irradiation will also be presented. These experimental results will highlight the usefulness of the conductive infrared polarizer to many security and monitoring applications

Highly ordered tailored three-dimensional hierarchical nano/microporous gold–carbon architectures

The preparation and characterization of three-dimensional hierarchical architectures, consisting of monolithic nanoporous gold or silver films formed on highly ordered 3D microporous carbon supports, are described. The formation of these nano/microporous structures involves the electrodeposition or sputtering of metal alloys onto the lithographically patterned multi-layered microporous carbon, followed by preferential chemical dealloying of the less noble component. The resulting hierarchical structure displays a highly developed 3D interconnected network of micropores with a nanoporous metal coating. Tailoring the nanoporosity of the metal films and the diameter of the large micropores has been accomplished by systematically changing the alloy compositions via control of the deposition potential, plating solution and coarsening time. SEM imaging illustrates the formation of unique biomimetic nanocoral- or nanocauliflower-like self-supporting structures, depending on the specific preparation conditions. The new 3D hierarchical nano/microporous architectures allow for enhanced mass transport and catalytic activity compared to common nanoporous films prepared on planar substrates. The functionality of this new carbon–gold hierarchical structure is illustrated for the greatly enhanced performance of enzymatic biofuel cells where a substantially higher power output is observed compared to the bare microporous carbon substrate

µChemLab: twenty years of developing CBRNE detection systems with low false alarm rates

Gas Chromatography (GC) is routinely used in the laboratory to temporally separate chemical mixtures into their constituent components for improved chemical identification. This paper will provide a overview of more than twenty years of development of one-dimensional field-portable micro GC systems, highlighting key experimental results that illustrate how a reduction in false alarm rate (FAR) is achieved in real-world environments. Significantly, we will also present recent results on a micro two-dimensional GC (micro GCxGC) technology. This ultra-small system consists of microfabricated columns, NanoElectroMechanical System (NEMS) cantilever resonators for detection, and a valve-based stop-flow modulator. The separation of a 29-component polar mixture in less than 7 seconds is demonstrated along with peak widths in the second dimension ranging from 10-60 ms. For this system, a peak capacity of just over 300 was calculated for separation in about 6 s. This work has important implications for field detection, to drastically reduce FAR and significantly improve chemical selectivity and identification. This separation performance was demonstrated with the NEMS resonator and bench scale FID. But other detectors, suitably fast and sensitive can work as well. Recent research has shown that the identification power of GCxGC-FID can match that of GC-MS. This result indicates a path to improved size, weight, power, and performance in micro GCxGC systems outfitted with relatively non-specific, lightweight detectors. We will briefly discuss the performance of possible options, such as the pulsed discharge helium ionization detector (PDHID) and miniature correlation ion mobility spectrometer (mini-CIMS)

Organic residues in archaeology - the highs and lows of recent research

YesThe analysis of organic residues from archaeological materials has become increasingly important to our understanding of ancient diet, trade and technology. Residues from diverse contexts have been retrieved and analysed from the remains of food, medicine and cosmetics to hafting material on stone arrowheads, pitch and tar from shipwrecks, and ancient manure from soils. Research has brought many advances in our understanding of archaeological, organic residues over the past two decades. Some have enabled very specific and detailed interpretations of materials preserved in the archaeological record. However there are still areas where we know very little, like the mechanisms at work during the formation and preservation of residues, and areas where each advance produces more questions rather than answers, as in the identification of degraded fats. This chapter will discuss some of the significant achievements in the field over the past decade and the ongoing challenges for research in this area.Full text was made available in the Repository on 15th Oct 2015, at the end of the publisher's embargo period

Advances in structure elucidation of small molecules using mass spectrometry

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules

Nanoparticle modifications of photodefined nanostructures for energy applications.

The advancement of materials technology towards the development of novel 3D nanostructures for energy applications has been a long-standing challenge. The purpose of this project was to explore photolithographically defineable pyrolyzed photoresist carbon films for possible energy applications. The key attributes that we explored were as follows: (1) Photo-interferometric fabrication methods to produce highly porous (meso, micro, and nano) 3-D electrode structures, and (2) conducting polymer and nanoparticle-modification strategies on these structures to provide enhanced catalytic capabilities and increase conductivity. The resulting electrodes were then explored for specific applications towards possible use in battery and energy platforms