Modeling electrodeposited NI80Fe20 and the electrolytes boundary conditions' influence on the mechanical properties, 2009

A Micro-electro-mechanical system (MEMS) gas turbine generator is currently under development. This device uses electrodeposited NisoFezo (thin film) as a structural material in the high speed rotating micro-generator used to convert mechanical energy to electrical energy. For structural applications, the materials' mechanical properties are vital for the design. However, for electrodeposited NisoFezo, currently, there is not any published data regarding its mechanical Properties. Therefore, the goal of this research is to model the mechanical properties of electrodeposited Ni80Fe20 as a function of three critical electrolytes variables: agitation, current density, and temperature. In achieving this goal, a typical off-the- shelf nickel iron electroplating solution was used to fabricate the Ni80Fe2~ test specimens. A 2k Factorial Analysis and Design of Experiments was used to identify the critical variables and boundary conditions, and a new Micro/Nano Testing System was designed and developed to measure the mechanical properties. Finally, a linear regression analysis was conducted to model Young's Modulus and Ultimate Strength as a function of the three critical electrolytes variables

Design, characterization and testing of a thin-film microelectrode array and signal conditioning microchip for high spatial resolution surface laplacian measurement.

Cardiac mapping has become an important area of research for understanding the mechanisms responsible for cardiac arrhythmias and the associated diseases. Current technologies for measuring electrical potentials on the surface of the heart are limited due to poor spatial resolution, localization issues, signal distortion due to noise, tissue damage, etc. Therefore, the purpose of this study is to design, develop, characterize and investigate a custom-made microfabricated, polyimide-based, flexible Thin-Film MicroElectrode Array (TFMEA) that is directly interfaced to an integrated Signal Conditioning Microchip (SCM) to record cardiac surface potentials on the cellular level to obtain high spatial resolution Surface Laplacian (SL) measurement. TFMEAs consisting of five fingers (Cover area = 4 mm2 and 16 mm2), which contained five individual microelectrodes placed in orthogonal directions (25-µm in diameter, 75-µm interelectrode spacing) to one another, were fabricated within a flexible polyimide substrate and capable of recording electrical activities of the heart on the order of individual cardiomyocytes. A custom designed SCM consisting of 25 channels of preamplification stages and second order band-pass filters was interfaced directly with the TFMEA in order to improve the signal-to-noise ratio (SNR) characteristics of the high spatial resolution recording data. Metrology characterization using surface profilometry and high resolution Scanning Electron Microscope (SEM) indicated the geometry of fabricated TFMEAs closely matched the design parameters \u3c 0.4%). The DC resistances of the 25 individual micro electrodes were consistent (1.050 ± 0.026 kO). The simulation and testing results of the SCM verified the pre-amplification and filter stages met the designed gain and frequency parameters within 2.96%. The functionality of the TFMEA-SCM system was further characterized on a TX 151 conductive gel. The characterization results revealed that the system functionality was sufficient for high spatial cardiac mapping. In vivo testing results clearly demonstrated feasibility of using the TFMEA-SCM system to obtain cellular level SL measurements with significantly improved the SNRs during normal sinus rhythm and Ventricular Fibrillation (VF). Local activation times were detected via evaluating the zero crossing of the SL electro grams, which coincided with the gold standard (dV/dt)min of unipolar electro grams within ± 1%. The in vivo transmembrane current densities calculated from the high spatial resolution SLs were found to be significantly higher than the transmembrane current densities computed using electrodes with higher interelectrode spacings. In conclusion, the custom-made TFMEASCM systems demonstrated feasibility as a tool for measuring cardiac potentials and to perform high resolution cardiac mapping experiments

The manufacture and characterisation of microscale magnetic components.

Abstract unavailable please refer to PD

Fabrication and characterization of nanostructured magnetic particles for applications in data storage

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Electronic version available online.Includes bibliographical references (p. 141-147).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Arrays of nanostructured magnetic particles ('nanomagnets') have potential applications in ultra-high-density data storage devices and dynamic magnetic memories, and are model systems for the study of magnetic phenomena at deep sub-micron length scales. We use interference lithography to pattern 200 nm-period arrays of nickel and cobalt nanomagnets. The nickel and cobalt are deposited via electroplating or evaporation/lift-off processes. Magnetometry techniques are used to characterize the bulk magnetic behavior of the arrays. Magnetic force microscopy is used to image the stray magnetic fields of individual nanomagnets as well as to measure particle switching fields. We compare our experimental results to predictions based on micromagnetic models and models of magnetostatic interactions. In particular, the influence of shape, size, inter-particle spacing and material properties on the remanence state of nanomagnets is evaluated. Finally, we examine the suitability of the fabricated nanomagnet arrays for applications in magnetic data storage.by Maya S. Farhoud.Ph.D

Electrodeposited nanoscale multilayers of Invar with copper

Materials with low thermal expansion coefficients (CTEs) that will survive temperature cycling are of interest in a variety of applications on the microscale, including actuation, precision assembly, and injection mold fabrication. Invar alloys exhibit a low positive coefficient of thermal expansion ranging between 0.2 – 1.2 µm/m-°C at room temperature. The electrodeposition process for fabricating nanoscale multilayers of Invar and copper in micro-patterns was characterized to assess their value in various MEMS applications. In an ongoing effort to maintain a stable CTE and effectively control the grain growth of Invar, nano-multilayers of near Invar-like FeNiCu and copper were electrodeposited into a pattern of 100µm tall microposts. A harder material than Invar, which could be used in mold insert and sensing applications, was of interest. Characterization of the FeNiCu electrolyte was done on rotating Hull Cell to determine the exact Invar plating range. EDXRF composition measurements showed that an iron to nickel ratio of Invar composition was obtained for current densities between 52.5 - 56 mA/cm², and copper alone was plated between 0.5 - 1 mA/cm². Microposts were fabricated using the LIGA microfabrication process and 100µm diameter by 100µm tall posts with fixed thickness (12.5nm) FeNiCu layers were deposited alternating with 1 nm, 4 nm, 5 nm, 7 nm, and 9 nm thick copper layers using a two level current density pulse. The presence of the nanoscale multilayers was confirmed by TEM. Multilayer microposts were tested for their thermal expansion behavior to study the effect of varying the copper layer thickness on the response to heating from ambient to 300°C. As deposited, the multilayer alloy exhibited a negative CTE; for a 2.5 nm thick Cu layer the CTE was -3.28µm/m-°C up to 150°C and more negative for higher temperatures. Two subsequent heating/cooling cycles resulted in the material exhibiting a positive CTE, where the multilayer provided energy for the reconfiguration of the alloy into a more stable, positive CTE form, comparable to bulk Invar. The average microhardness of the as-deposited multilayer measured 50 on the Rockwell C scale and was comparable with H13 and P20 type tool steels

Fundamental efforts for improving the sensitivity of magnetic resonance force microscopy

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011."July 2011." Cataloged from PDF version of thesis.Includes bibliographical references (p. 20-24).Introduction: Complete understanding of the mechanisms of biological processes, indispensable for the rational design and testing of therapeutic strategies, can be greatly facilitated by easy and rapid access to macromolecular structures at the atomic resolution. As of 2011, a general method for rapid rendering of macromolecular and cellular structures with atomic resolution represents both a major challenge and a major need in science. Such a method would prove all the more valuable to understanding the conformational complexities of protein misfolding diseases and amyloid formation phenomena , caused by complex networks of structural transition reactions linking the monomeric, oligomeric, and polymorphic fibrillar forms of disease-causing proteins, the structures of which have only been rigorously characterized in a small number of cases. To date, the majority of protein and RNA structures known have been solved by either X-ray crystallography or by NMR spectroscopy. Many requirements on the sample prevent these methods from being generally applicable to biological specimens. First, since X-ray crystallography and NMR spectroscopy are techniques based on assessing the average properties of a macroscopic sample, a high degree of sample heterogeneity undermines their ability to solve structures. Second, X-ray crystallography requires the sample protein to form ordered crystals. However, the procedure for crystallizing proteins remains a daunting trial-and-error process and important proteins like membrane proteins are impossible to crystallize in their native forms. Recent advances in solid state NMR (ssNMR) spectroscopy have made it possible to study membrane proteins, but the technique is still limited by protein size and by the need for order, at least at the local level. For these reasons, the structural studies of macromolecule that contain high degrees of conformational heterogeneity and that are large in size have remained challenging, rare, and largely tackled, with difficulty, by computational approaches.by Ye Tao.S.M

Permalloy nanowires/graphene oxide composite with enhanced conductive properties

Carbon–metal-based composites arise as advanced materials in the frontiers with nanotechnology, since the properties inherent to each component are multiplexed into a new material with potential applications. In this work, a novel composite consisting of randomly oriented permalloy nanowires (Py NWs) intercalated among the sheets of multi-layered graphene oxide (GO) was performed. Py NWs were synthesized by electrodeposition inside mesoporous alumina templates, while GO sheets were separated by means of sonication. Sequential deposition steps of Py NWs and GO flakes allowed to reach a reproducible and stable graphene oxide-based magnetic assembly. Microscopic and spectroscopic results indicate that Py NWs are anchored on the surface as well as around the edges of the multi-layered GO, promoted by the presence of chemical groups, while magnetic characterization affords additional support to our hypothesis regarding the parallel orientation of the Py NWs with respect to the GO film, and also hints the parallel stacking of GO sheets with respect to the substrate. The most striking result remains on the electrochemical performance achieved by the composite that evidences an enhanced conductive behaviour compared to a standard electrode. Such effect provides an approach to the development of permalloy nanowires/graphene oxide-based electrodes as attractive candidates for molecular sensing devices.Fil: Arciniegas Jaimes, Diana Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Márquez, Paulina. Universidad de Santiago de Chile; ChileFil: Ovalle, Alexandra. Universidad de Santiago de Chile; ChileFil: Escrig Murúa, Juan Eduardo. Universidad de Santiago de Chile; ChileFil: Linarez Pérez, Omar Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Bajales Luna, Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Optoelectronic integration using the magnetically assisted statistical assembly technique : initial magnetic characterization and process development

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 99-101).The commercial integration of optoelectronic devices heavily relies on hybrid techniques such as wire bonding and flip-chip bonding. These methods are limited in the scale and flexibility in integration. Research focused on optoelectronic integration is performed using numerous techniques such as direct epitaxy, full-scale wafer bonding, and self-assembly. Magnetically Assisted Statistical Assembly (MASA) is an example of the latter technique and improves scale and flexibility by enabling the simultaneous integration of large numbers of individual devices. This thesis work is focused on the demonstration of the MASA concept through characterization of the magnetic materials forming the foundation for this technique and development of an adequate process technology. Both, the magnetic characteristics and the process technology required to integrate the technology are presented along with results of the integration.by Joseph John Rumpler, II.S.M