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Microfabricated biochips are developed to continuously monitor cell population dynamics in a non-invasive manner. In the presented work we describe the novel combination of contact-less dielectric microsensors and microfluidics to promote biofilm formation for quantitative cell analysis. The cell chip consists of a polymeric fluidic (PDMS) system bonded to a glass wafer containing the electrodes while temperature and fluid flow are controlled by external heating and pumping stations. The high-density interdigitated capacitors (microIDES) are isolated by a 550 nm multi-passivation layer of defined dielectric property and provide stable, robust and non-drifting measurement conditions. The performance of this detector is evaluated using various bacterial and yeast strains. The high sensitivity of the developed dielectric microsensors allows direct identification of microbial strains based on morphological differences and biological composition. The novel biofilm analysis platform is used to continuously monitor the dynamic responses of C. albicans and P. pastoris biofilms to increased shear stress and antimicrobial agent concentration. While the presence of shear stress triggers significant changes in yeast growth profiles, the addition of 0.5 microg mL(-1) amphotericin B revealed two distinct dynamic behaviors of the C. albicans biofilm. Initially, impedance spectra increased linearly at 30 Omega h(-1) for two hours followed by 10 Omega h(-1) (at 50 kHz) over 10 hours while cell viability remained above 95% during fungicide administration. These results demonstrate the ability to directly monitor dielectric changes of sub-cellular components within a living cell population.

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Semiconductor heterostructures, such as double-barrier resonant tunnelling diodes and superlattices, are nowadays used for many applications. One very versatile and powerful method to study electronic transport in heterostructures is hot electron spectroscopy. Hot electron spectroscopy can be carried out in two complementary versions: device-based techniques usually employ so-called hot electron transistors (HETs), while ballistic electron emission microscopy (BEEM) uses a scanning tunnelling microscope (STM) as the source of ballistic electrons.In this review, spectroscopic results obtained by these two methods are compared and discussed. It is shown that BEEM results are strongly influenced by electron refraction effects, while the behaviour of HET devices is dominated by inelastic scattering effects in the base and drift region of the device. Thus, STM-based BEEM/S and HET-based spectroscopy are genuinely complementary methods, which yield supplementary results.

Zinc metal nanowires (NWs) of two different morphologies have been synthesized in a cold-wall physical vapor deposition (CWPVD) chamber at high vacuum conditions and growth temperatures of 150 degrees C. Substrates initially seeded by gold or platinum crystals show NWs of wool-like and/or unidirectional morphologies. Transmission electron microscopy (TEM) studies revealed that the rodlike NWs consist of single-crystalline Zn covered with a thin native oxide. NWs of wool-like morphology are suppressed using platinum as the seed metal. NW growth proceeds via vapor-solid (VS) kinetics without any catalyst particles on the wire tips. The highest observed growth rates exceed the Zn deposition rate by factors up to 860, indicating the dominant role of surface diffusion of Zn adatoms, also along the NWs. The surface diffusion length of Zn adatoms on the NW side facet is determined to be 39 mum. Direct impingement of precursor atoms on the NW tip is not significant for the growth process.