The Ebola Virus Disease (EVD) outbreak in West Africa has been declared a public health emergency of international concern by the World Health Organization. The Ebola outbreak has led to the disruption of already fragile but essential health services and drug distribution systems; HIV clinical services in Liberia, Sierra Leone, and Guinea were particularly affected. Targeted approaches are necessary to protect the continuity of HIV treatment for people living with HIV and should be integrated within the broader Ebola response; this will save lives, prevent drug resistance, and decrease the likelihood of HIV transmission. (Disaster Med Public Health Preparedness. 2015;9:522–526)

Insight into dynamic electrochemical processes can be obtained with in situ electrochemical-scanning/transmission electron microscopy (ec-S/TEM), a technique that utilizes microfluidic electrochemical cells to characterize electrochemical processes with S/TEM imaging, diffraction, or spectroscopy. The microfluidic electrochemical cell is composed of microfabricated devices with glassy carbon and platinum microband electrodes in a three-electrode cell configuration. To establish the validity of this method for quantitative in situ electrochemistry research, cyclic voltammetry (CV), choronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were performed using a standard one electron transfer redox couple [Fe(CN)6]3−/4−-based electrolyte. Established relationships of the electrode geometry and microfluidic conditions were fitted with CV and chronoamperometic measurements of analyte diffusion coefficients and were found to agree with well-accepted values that are on the order of 10−5 cm2/s. Influence of the electron beam on electrochemical measurements was found to be negligible during CV scans where the current profile varied only within a few nA with the electron beam on and off, which is well within the hysteresis between multiple CV scans. The combination of experimental results provides a validation that quantitative electrochemistry experiments can be performed with these small-scale microfluidic electrochemical cells provided that accurate geometrical electrode configurations, diffusion boundary layers, and microfluidic conditions are accounted for.

A technique has been developed that allows the application of free-standing membranes of polymer adhesives used in microfabricated structures. The film is made free-standing by the application of the adhesive to a polymer template, followed by an adhesion step to a microfabricated substrate, and the final release of the film by the removal of the polymer template. It was found that the surface treatment used to treat the Teflon template made it adhere too strongly to the adhesive film for this application. The results show that Gel-Paks make a suitable template for the transference of polymer films over holes of at least micron size.

This paper presents the study of the strength of surface micromachined diaphragms. It is found that the diaphragm strength strongly depends on the diaphragm boundary conditions. A new fabrication technique which does not change the mask and fabrication process is proposed to improve the common step-up boundary condition. Test diaphragms with diameters from 200 µm to 800 µm and three different boundary conditions have been fabricated using silicon nitride/PSG and silicon nitride/polysilicon surface micromachining processes. Experimentally, it is found that the strength of the diaphragms is significantly improved with the new boundary conditions. The application of this technique to other surface micromachined structures is also described.

We characterize in-situ the adhesion of surface micromachined polysilicon beams subject to controlled humidity ambients. Beams were freed by supercritical CO2drying. Consistent adhesion results were obtained using a post-treatment in an oxygen plasma which rendered the microbeams uniformly hydrophilic. Individual beam deformations were measured by optical interferometry after equilibration at a given relative humidity (RH). Validation of each adhesion measurement was accomplished by comparing the deformations with elasticity theory. The data indicates that adhesion increases exponentially with RH from 30% to 95%, with values from 1 mJ/m2 to 50 mJ/m2. Using the Kelvin equation, we show that the data should be independent of RH if a smooth interface is considered. By modeling a rough interface consistent with atomic force microscopy (AFM) data, the exponential trend is satisfactorily explained.

Thin polymer layers gain importance as interlevel dielectrics in microelectronic devices. One major drawback of this class of material is instability of mechanical properties under changing climatic condition. The paper deals with evaluation of the bulge test as complementary method for investigation of humidity induced alterations of mechanical properties. It describes measurement of intrinsic as well as humidity induced stress in polymer layers. The given results agree very well with those obtained by substrate bending. Furthermore, bulge testing proved the assumption of earlier work, that change of mechanical stress is due to a humidity induced swelling process that can be described phenomenologically by expansion coefficient and a biaxial Young's modulus independent from relative humidity. Results are given and discussed for two types of polyimide.

The improvement of thickness distribution and crystallinity in ZnO thin films prepared by radio frequency (rf) planer magnetron sputtering has been studied. Optimum thickness distribution of less than ± 2.2% in a 3-inch wafer is obtained by changing the substrate angle to the ZnO target and is in accordance with cosine law. The c-axis orientation perpendicular to the silicon substrate is confirmed by x-ray diffraction. The stress of ZnO thin films is larger than 0.3GPa and its distribution is independent of the substrate angle that is set at a slant to the optimum angle for thickness distribution. These results indicate that thickness distribution of ZnO thin films heavily depends on the substrate angle, while the stress and its distribution are independent of the setting angle of the substrate. Stress distribution is attributed to the distribution of argon ions and sputtered molecules impinging a wafer.

Sagging of suspended or laminated structures is a common problem in the processing of Low Temperature Co-Fired Ceramics (LTCC). These glass-ceramic composites are susceptible to plastic deformation upon lamination, or under the stress of body forces once the glass transition temperature of the glass binder is reached during processing. We have designed and fabricated, using the conventional methods of LTCC fabrication, meso-scale structures (ranging in size from 100 mm to 1 cm) to quantify and seek control strategies for this problem. We have implemented bridge structures and membranes to emulate most of the conventional structures encountered during packaging or sensor (actuator) device fabrication.

We have observed that when an LTCC tape with holes larger than 400 µm in diameter is laminated, the tapes above and below deform into the cavity. For smaller diameters, deformation is negligible. Bridging structures can be compensated for the potential effect of body forces by screen-printing a thick film over-layer which exert internal tensile stresses on sintering. This can often yield straight bridges. The use of fugitive phase materials, which disappear or flow during firing, is another way of supporting bridging structures. Several of these strategies have been explored, and results are presented.

The primary objective of this work is to carry out a combined experimental and numerical investigation of the mechanical stress induced during the Ti-silicidation of narrow lines spaced by a Poly Buffered Local field oxide. Therefore micro-Raman spectroscopy (μRS) measurements of local mechanical stress are combined with simulations by Finite Element Modeling (FEM). Numerical determination of the local stress in the Si-substrate by means of FEM becomes more and more important when scaling down the device dimensions because the spatial resolution of μRS is limited at about 1μm and because the stress in the Si-substrate underneath silicided lines can not be detected using pRS unless the silicide is very thin. The Finite Element analysis was done using SYSTUS and involves a two dimensional plane strain thermo-elastic formulation. A good agreement was obtained between the FEM simulations and the μRS data for line widths above 1Bm making the extrapolation of the FEM to line widths smaller than I1m an attractive alternative for μRS.

A newly developed approach to thin-film tensile testing has been utilized for evaluating ultra-thin-films of about 60-100 nm in thickness. Thin sputtered metal films deposited on 3.5 gm thick polyimide film substrates were tested using a Mesotronix nanotensiometer. Modifications to sample handling and zero strain calibration helped to improve testing reproducibility. The response of a thin-film metal was determined by subtracting the response of the polyimide carrier film from that of the metal-on-polyimide composite. Stress-strain curves for two amorphous alloys sputtered from Al-25 at% Ti and Nb-25 at% Al targets exhibited well-defined elastic regions followed by brittle behavior. The ultimate tensile strengths (UTS) were about 1200 MPa for the Al-Ti and 1700 MPa for the Nb-Al, both of which occurred near the elastic strain limit of about 2%. After recrystallization at 280°C for an hour, the Al-Ti film showed what appears to be an upper and lower yield point, in addition to strain hardening. Initial yielding occurred at a strain of about 1.2% and a stress of about 800 MPa, while the UTS of about 1000-1060 MPa occurs at strains as high as 9%. Stress relaxation measurements performed on both the amorphous and the recrystallized films showed lower values of stress relaxation at 1% strain compared to low alloy polycrystalline Al films.

Measurements are reported on the mechanical properties of high-aspect-ratio micromechanical structures formed using a conventional 0.5-µm CMOS process. Composite structures are etched out of the CMOS dielectric, aluminum, and gate-polysilicon thin films using a post-CMOS CHF3:O2 reactive-ion etch and followed by a SF6 :O2silicon etch for release. Microstructures have a height of 5 µm and beam widths and gaps down to 1.2 µm. Properties are strongly dependent on the relative metal and dielectric content of the beams. Beams with three metal conductors and polysilicon have an effective Young's modulus of 62 GPa, residual stress of -29 MPa, and an average out-of-plane radius of curvature of 1.9 mm. Maximum Young's modulus variation is 3 GPa die-todie, and is 9 GPa between two runs. Die-to-die variation of stress and stress gradient is poor for many beam compositions, however local matching on a die is very good. Cracking is induced in a resonant fatigue structure at 620 MPa of repetitive stress after over 50 million cycles.

The objective of this work was to develop an improved wet etch-stop technology for silicon micromachining. To establish a reference for process improvement, the diffusion process currently used to fabricate p++ Si:B etch stops was comprehensively investigated. Subsequently, a novel germanium- based epitaxial etch-stop technology was developed.

A range of techniques were used to study p++ silicon layers created by boron diffusion into (001) silicon wafers. The results revealed gradients in boron and lattice constant, as well as a graded three- dimensional dislocation array from lattice-mismatch stress. The gradients in boron concentration and dislocation density can lead to curl in micromachined structures. Although annealing steps can remove the boron gradient, a flat membrane will be a tenuous balance.

Epitaxial films of p++Si:B and strain-compensated p++Si1-xGex:B can remove composition gradients and improve process control. However, it is undesirable to depend on p-type layers doped at levels near the solubility limit to prevent etching. We have therefore developed a unique etch stop created from relaxed SiGe alloys. Etch-stop behavior quite similar to heavily boron-doped silicon has been demonstrated in undoped silicon-germanium. Neither strain nor defects are responsible for the etch-stop behavior. A model is proposed based on energy band structure and a SiOx passivation mechanism.

Raman microscopy, using a novel line focus configuration, has been used here to study boron concentration distributions and depth profiles in silicon for two different sources of dopant. Changes in the Raman phonon peak frequency for boron doped silicon have been calibrated against concentration by comparison with SIMS data and a relationship between Raman shift and lattice strain has been obtained.

Nutrigenomics is the study of how constituents of the diet interact with genes, and their products, to alter phenotype and, conversely, how genes and their products metabolise these constituents into nutrients, antinutrients, and bioactive compounds. Results from molecular and genetic epidemiological studies indicate that dietary unbalance can alter gene–nutrient interactions in ways that increase the risk of developing chronic disease. The interplay of human genetic variation and environmental factors will make identifying causative genes and nutrients a formidable, but not intractable, challenge. We provide specific recommendations for how to best meet this challenge and discuss the need for new methodologies and the use of comprehensive analyses of nutrient–genotype interactions involving large and diverse populations. The objective of the present paper is to stimulate discourse and collaboration among nutrigenomic researchers and stakeholders, a process that will lead to an increase in global health and wellness by reducing health disparities in developed and developing countries.