Mark Schadt

Core@shell nanomaterials: gold-coated magnetic oxide nanoparticles

The study of core@shell magnetic nanoparticles has a wide range of applications because of the unique combination of the nanoscale magnetic core and the functional shell. This report highlights some of the recent findings in the investigation of the synthesis, characterization and application of one important class of core@shell magnetic nanoparticles, i.e., magnetic nanoparticles coated with a gold shell (MNP@Au). The gold shell imparts the magnetic nanoparticles with many intriguing functional properties. Areas specifically highlighted in this report include strategies for the synthesis of MNP@Au nanoparticles, characterization of the core@shell nanostructures, and exploration of potential applications of the core@shell nanomaterials in terms of biological and catalytic interfacial reactivities. Implications of some of the research findings to address both fundamental and practical issues are also briefly discussed in an effort to further broaden the rapidly-emerging field of core@shell magnetic nanoparticles.

Thin film assemblies of molecularly-linked metal nanoparticles and multifunctional properties.

The use of metal nanoparticles as building blocks toward thin film assembly creates intriguing opportunities for exploring multifunctional properties. Such an exploration requires the ability to engineer the size, shape, composition, and especially interparticle properties in nanoparticle assemblies for harnessing the collective properties of the nanoscale building blocks. This article highlights some of the important findings of our investigations of thin film assemblies of molecularly linked nanoparticles for exploiting their multifunctional and collective properties in molecular recognition and chemical sensing. The thermally activated processing approach presents a viable pathway for nanoengineering metal, alloy, and core-shell nanoparticles as building blocks. The molecular mediator-templating approach offers an effective strategy to thin film assemblies of the nanoscale building blocks that impart multifunctional properties. In such thin film assemblies, the interparticle interactions and structures dictate the correlation between the nanostructural parameters and the optical and electrical properties. By highlighting selected examples involving ligand-framework binding of ionic species at the film/liquid interface and electrical responses to molecular sorption at the film/gas interface, the multifunctional properties of the thin film assemblies are further discussed in terms of interparticle covalent, hydrogen bonding, ionic, or van der Waals interactions in a framework-type architecture for the creation of molecular recognition and chemical sensing sites that can be tuned chemically or electrochemically. Implications of these insights to expanding the exploration of nanoparticle thin film assemblies for a wide range of technological applications are also discussed.

A Wearable Flexible Hybrid Electronics ECG Monitor

Flexible hybrid electronics (FHE) integrate both traditional printed circuits, solder assembled standard and thinned silicon chips along with printable electronic materials and sensors. The combination results in high performance from thin, light weight, flexible devices that potentially could be manufactured at low cost. In this paper, flexible hybrid electronics technology is being used to develop a wearable ECG and skin temperature monitor. All components and materials were commercially available, and all fabrication processes were executed in manufacturing environments. The monitor is composed of a flexible polyimide substrate with printed ECG electrodes, a printed thermistor, and connecting traces printed on one surface, and the electronic components mounted on other. Both sides have copper metal circuits connected by copper plated through hole vias (THV). ECG signals are amplified, preconditioned and wirelessly transmitted via Bluetooth to a nearby handheld mobile phone or computer. The wearable monitor is 2x2 inches in size and has been demonstrated to produce high fidelity ECG signals at the host from both certified archived human ECG signals and ECG signals from human volunteers. The monitor reproduced the archived signals at the host from which a set of clinical parameters were calculated that closely matched those of the archived signals. Manufacturing challenges and device reliability will be discussed. Current work includes building upon this platform and integration of other monitoring and sensor devices included those that monitor for biomarkers in sweat. This work was sponsored by the NanoBio Manufacturing Consortium administered by the Flextech Alliance and funded by the US Air Force Research Laboratory.

Assessing the Role of Capping Molecules in Controlling Aggregative Growth of Gold Nanoparticles in Heated Solution

This report describes findings of an investigation of the role of capping molecules in the size growth in the aggregative growth of pre-formed small-sized gold nanoparticles capped with alkanethiolate monolayers toward monodispersed larger sizes. The size controllability depends on the thiolate chain length and concentration in the thermal solution. The size evolution in solution at different concentrations of alkanethiols is analyzed in relation to adsorption isotherms and cohesive energy. The size dependence on thiolate chain length is also analyzed by considering the cohesive energy of the capping molecules, revealing the importance of cohesive energy in the capping structure. Theoretical and experimental comparisons of the surface plasmonic resonance optical properties have also provided new insights into the mechanism, thus enabling the exploitation of size-dependent nanoscale properties.

Effect of lamination on the bending fatigue life of copper coated PET substrate

While todays display technology is mainly based on rigid-based substrate, flexible display technology has been significantly growing since the last decade. However, Flexible displays are susceptible to many types of stresses during processing and usage. Thin films on flexible substrate are sensitive to ambient conditions. Therefore devices are usually laminated with a protective layer. In this study high cyclic bending fatigue experiments were conducted on 2000 oA thick copper thin films sputter deposited on 127 μm polyethylene terephthalate (PET) substrate laminated with another 127 μm PET layer. High magnification images were used to observe crack initiation and propagation in the thin film layer. Initial results showed a great influence of laminate layer on stress reduction in the thin film. Furthermore, a lamination layer causes cracks to spread out on a larger area with fine cracks and therefore reduce the chance of the cracks to meet and grow.

Z-Axis Interconnection in Organic Packaging

Greater I/O density at the die level, more demanding performance requirements, and the continued desire to package more function into smaller devices is driving the need for improved wiring density and a concomitant reduction in feature sizes for electronic packages. Traditionally, greater wiring densities have been achieved by reducing the dimensions of vias, lines, and spaces, while also increasing the number of wiring layers. However, each of these methods possesses inherent limitations in todays most challenging multi-chip module (MCM) and system-in-package (SiP) applications that also demand reduction in size, weight and power (SWaP). These applications are forcing new methods to be developed for achieving greater wiring densities while also meeting the cost for performance challenges that exist within this industry. One method of extending wiring density beyond the limits imposed by todays traditional approaches is the strategy of making metal-to-metal z-axis interconnection of subcomposites durin...