Robocasting, a solid freeform fabrication technique, was used to develop lattices of hydroxyapatite (HA) that show promise as load‐bearing scaffolds for bone repair. Additionally, the lattice scaffolds can be shaped into customized implants. A computed tomography (CT) scan of a damaged mandible was utilized to noninvasively design a lattice implant that could fill the damaged region. In a case study, the fit of the custom lattice scaffold was tested in a damaged mandible and “fit like a glove.” Such implants may be able to replace numerous autograft procedures, thereby reducing surgical cost and complications associated with bone harvesting surgery.

Micro-electro discharge machining (EDM) is a subtractive meso-scale machining process. The Agie Excellence 2F wire micro EDM is capable of machining with a 25 micron diameter wire electrode and positioning the work piece to within ±1.5 microns. The over-burn gap can be controlled to within 3 microns to obtain a minimum feature radius of about 16 microns while achieving submicron surface finish and an imperceptible recast layer. For example, meso-scale gears that require vertical sidewalls and contour tolerances to within 3 microns can be wire EDMed into a variety of conductive materials. Material instabilities can affect the dimensional precision of machined meso-scale parts by material relaxation during the machining process. A study is done to investigate the machining performance of the wire micro EDM process by machining a high aspect ratio meso-scale part into a variety of metals (e.g. 304L stainless steel, Nitronic 60 Austentic Stainless, Beryllium Copper, and Titanium). Machining performance parameters such as, profile tolerance, perpendicularity, and repeatability are compared for the different materials. Pertinent inspection methods desirable for meso-scale quality assurance tasks are also evaluated. Sandia National Laboratories is developing meso-scale electro-mechanical components and has an interest in the assembly implications of piece parts fabricated by various meso-scale manufacturing processes. Although the wire EDM process is typically used to fabricate 2½ dimensional features, these features can be machined into a 3 dimensional part having other features such as hubs and chamfers to facilitate assembly.

A bismuth telluride alloy-based thermoelectric generator with high-aspect ratio, free-standing legs was fabricated. Such legs are desirable for efficient generator performance from low-grade heat sources but are difficult to assemble because they are fragile and difficult to handle and position. Plunge and wire electro-discharge machining (EDM) were used to produce 150 lm  300 lm legs, approximately 6-mm long, with high fidelity. Removal of recast material from EDM was necessary for good adhesion of metallization, but sputter etching was found to deteriorate the mechanical strength of the contacts. A wet chemical cleaning process was developed instead that resulted in good adhesion under test conditions. Au was preferred for designs where interconnects could be patterned directly on the module. Module figure of merit (ZT) was 0.72, close to the 0.85 value expected from bulk material property measurements. Impedance spectroscopy and the Harman technique were shown to significantly underestimate module ZT in the present test configuration. Shear and fatigue testing were performed on arrays of high-aspect ratio legs. Legs survived over 10 4 cycles of shear loading at 90% of the load to failure.

A 100X magnification, ± 2.5° field of view micro-concentrating optical system has been developed for a microsystems-enabled photovoltaic (MEPV) prototype module using 250 µm diameter multi-junction "stacked" PV cells.

Abstract. Recent development of a novel micro-scale PV/CPV technology is presented. The Wafer Integrated Microscale PV approach (WPV) seamlessly integrates multijunction micro-cells with a multi-functional silicon platform that provides optical micro-concentration, hybrid photovoltaic, and mechanical micro-assembly. The wafer-embedded microconcentrating elements is shown to considerably improve the concentration-acceptance-angle product, potentially leading to dramatically reduced module materials and fabrication costs, sufficient angular tolerance for low-cost trackers, and an ultra-compact optical architecture, which makes the WPV module compatible with commercial flat panel infrastructures. The PV/CPV hybrid architecture further allows the collection of both direct and diffuse sunlight, thus extending the geographic and market domains for cost-effective PV system deployment. The WPV approach can potentially benefits from both the high performance of multijunction cells and the low cost of flat plate Si PV systems.