Due to advances in telemedicine, mobile medical care, wearable health monitoring, and electronic skin, great efforts have been directed to non-invasive monitoring and treatment of disease. These processes generally involve disease detection from interstitial fluid (ISF) instead of blood, and transdermal drug delivery. However, the quantitative extraction of ISF and the level of drug absorption are greatly affected by the individual’s skin permeability, which is closely related to the properties of the stratum corneum (SC). Therefore, measurement of SC impedance has been proposed as an appropriate way for assessing individual skin differences. In order to figure out the current status and research direction of human SC impedance detection, investigations regarding skin impedance measurement have been reviewed in this paper. Future directions are concluded after a review of impedance models, electrodes, measurement methods and systems, and their applications in treatment. It is believed that a well-matched skin impedance model and measurement method will be established for clinical and point-of care applications in the near future.

Articles you may be interested inGrowth of InP on GaAs (001) by hydrogen-assisted low-temperature solid-source molecular beam epitaxy

Copper indium gallium di‐selenide (CIGS) solar cells from Global Solar Energy, Inc. and development cells from another manufacturer are laminated in non‐barrier packaging and exposed to a variety of temperature and humidity conditions, and measured degradation rates fit to a kinetic expression. The kinetic constants are then used in a life model that is based on time‐dependent mass and energy balances governing module temperature and the diffusion of water through a module package subjected to weather conditions. Cells with an aluminum‐doped zinc oxide window layer degrade approximately 25× faster than cells having an indium tin oxide window layer, and so require much lower permeability barrier films in a flexible package. The electrically conducting adhesive used to connect bottom and top contact to solder‐coated ribbons can be a major factor in degradation. This difference may only be apparent at lower temperatures, which drastically affects real‐world lifetime. Preliminary Florida and Arizona data confirm this. The key assumption in the model is that the instantaneous rate of degradation is proportional to the relative saturation of the encapsulant with water (0–100%), and not the absolute concentration of water in the encapsulant (10−3–10−2 g/cm3). This leads to the model prediction that it is only the diffusion time constant tc = LESE/WVTR that determines the degradation and life of a packaged cell and that thicker encapsulants with higher water solubility will significantly extend cell life. Experimental data for three different encapsulant materials with and without a moisture barrier film confirm these predictions. Copyright © 2011 John Wiley & Sons, Ltd.

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We have grown N-rich, dilute Sb GaN1−xSbx alloys by low temperature molecular beam epitaxy. At low growth temperature of <100 °C the material loses crystallinity and becomes primarily amorphous with small crystallites of 2–5 nm at a Sb composition of >4 at. %. Despite the different microstructures found for GaN1−xSbx alloys with different composition, the absorption edge shifts continuously from 3.4 eV (GaN) to close to 1 eV for samples with Sb content >30 at. %. GaN1−xSbx alloys with less than 5 at. % Sb show sufficient bandgap reduction (∼2 eV), making them suitable for photoelectrochemical applications.

The formation of twin is common during GaAs(111) and GaN(0001) molecular beam epitaxy (MBE) metalorganic chemical vapor deposition growth. A stacking fault in the zinc-blende (ZB)(111) direction can be described as an insertion of one monolayer of wurtzite structure, sandwiched between two ZB structures that have been rotated 60° along the growth direction. GaAs(111)A/B MBE growth within typical growth temperature regimes is complicated by the formation of pyramidal structures and 60° rotated twins, which are caused by faceting and stacking fault formation. Although previous studies have revealed much about the structure of these twins, a well-established simple nondestructive characterization method which allows the measurement of total aerial density of the twins does not exist at present. In this article, the twin density of AlGaAs layers grown on 1° miscut GaAs(111)B substrates has been measured using high resolution x-ray diffraction, and characterized with a combination of Nomarski microscopy, atomic force microscopy, and transmission electron microscopy. These comparisons permit the relationship between the aerial twin density and the growth condition to be determined quantitatively.

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Both optical transmission spectroscopy and photothermal deflection spectroscopy are used to determine the spectra of C70 thin films over a wide energy range (0.6–6.5 eV). Based on a molecular orbital model, the optical transitions for the C70 thin film are analyzed. The weak absorption spectra of C70 thin films are similar to that of an amorphous semiconductor. The optical energy gap is derived by a Tauc plot as 1.66 eV. The gap region can be described in terms used for amorphous semiconductors, having features such as an Urbach edge and subgap defect absorption, which are interpreted as a broadening due to disorder or impurities. The effects of the deflection medium on the weak absorption spectra of C70 films are discussed.