With soft micro‐ and nanopatterned materials becoming increasingly useful for various, optical, mechanical, electronic, microfluidic, and optofluidic devices, the extension of this paradigm to a pure protein‐based material substrate provides entirely new options for such devices. Silk fibroin combines the properties of an ideal nanoimprint resist with superior optical quality and biocompatibility making it a new technology platform that seamlessly combines nanophotonics, biopolymeric, and biocompatible materials.

Micromachined fluid-filled variable impedance waveguides intended to mimic the mechanics of the passive mammalian cochlea have been fabricated and experimentally examined. The structures were microfabricated with dimensions similar to those of the biological system. Experimental tests demonstrate acoustically excited traveling fluid-structure waves with phase accumulations between 1.5 and 3 radians at the location of maximum response. The resulting measured frequency-position mapping function, with similarities to that observed in the cochlea, is presented. Results for both isotropic and orthotropic membranes are reported, demonstrating that the achieved orthotropy ratio of 8:1 in tension is insufficient to produce the sharp filtering observed in animal experiments and many computational models that use higher ratios. It is also shown experimentally that high viscosity fluids must be used to provide sufficient damping to avoid the formation of a nonphysiological standing wave pattern. A mathematical model incorporating a thin-layer viscous, compressible fluid approximation coupled to an orthotropic membrane model is validated against experimental results. The work presented herein is motivated by the possibility of producing microfabricated cochlear-like filters, thus the structure is designed for production in a scalable microfabrication process.acoustic ͉ micro-electro-mechanical systems ͉ sensor ͉ viscosity T he cochlea is the organ in the inner part of the mammalian ear that is responsible for the transduction of acoustic signals into neurological signals. The typical human cochlea operates over a 3-decade frequency band, from 20 Hz to 20 kHz, covers 120 dB of dynamic range, and can distinguish tones that differ by Ͻ0.5% (1). The cochlea is also very small, occupying a volume of Ϸ1 cm 3 . Perhaps most importantly, the cochlea uses a mechanical process to separate audio signals into Ϸ3,500 channels of frequency information. Thus, the cochlea is a sensitive real-time mechanical frequency analyzer.The effectiveness of the cochlea as a time-frequency analyzer motivates our efforts to construct a hydromechanical analog that can be fabricated repeatably and in a batch fashion. Integration of sensing elements with the mechanical structure would result in a combined acoustic sensor͞filter with a unique operating modality. During the design of the mechanical structure, we also learn more about some aspects of the biological cochlea. von Békésy's (2, 3) observation of traveling waves on the basilar membrane (BM) of cadaver cochleae motivated the construction of a number of physical models of the cochlea. The first group of these models involved scaled-up versions of the cochlea. Helle's (4) model is seven times life size and exhibits tonotopic structure in the 25-to 800-Hz band. Chadwick et al. (5) built a 24 times life-size model and clearly show strong standing wave patterns and the resulting discrete resonances. Because of the standing wave nature of their response, a tonotopic map is not demonstrated (5). Lechner'...

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In this paper, two sets of experimental results to extract the two effective elastic moduli, the effective shear modulus, and the effective Poisson's ratio for the gerbil cochlear partition are analyzed. In order to accomplish this, a geometrically nonlinear composite orthotropic plate model is employed. The model is used to predict both out-of-plane and in-plane motion of the partition under a static finite area distributed load. This loading condition models the small, but finite size, probe tips used in experiments. Both in-plane and out-of-plane motion are needed for comparison with recent experimental results. It is shown that the spatial decay rate (the space constant) for the in-plane deflection is different than for the out-of-plane deflection, which has a significant effect on the derived partition properties. The size of the probe tip is shown to have little influence on the results. Results are presented for two types of boundary conditions. Orthotropy ratios determined from the experimental data are found to vary with longitudinal position and choice of boundary conditions. Orthotropy ratios (the ratio of the two elastic moduli) are in the range of 65 close to the base to 10 in the upper middle turn of the cochlea.

In ~10-5 M acidic aqueous solutions of Methyl Orange the rate constant at 25°for the recombination of a proton with the monoanion of the indicator is 2.9 ± 0.4 x 109 M-1 sec-1. This specific rate, determined by a spectrophotometric electric field jump relaxation technique, is significantly smaller than that expected for a diffusion-controlled ion recombination. An explanation for this result follows from a comparison with similar kinetic data for aqueous Methyl Red.

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There is no deployment strategy or capacity prediction available for wireless multiple-input-multiple-output (MIMO) communication systems inside underground mines. In such environments with low angular spread, the authors showed how antenna properties including antenna spacing, polarisation and height impact a 4 × 4-MIMO system performance. They used channel-frequency-response data near the 2.4 GHz obtained from measurements collected in a short underground mine, along with the recently developed multimode waveguide model. Several uniform-linear-array configurations were assessed for various propagation scenarios in the mine. They used the singular value, correlation coefficient and capacity analysis to compare their performance. Based on the results, they proposed an array orientation and element spacing, which provides sufficient spatial decorrelation among MIMO subchannels. The spatial decorrelation results are close to that of an i.i.d. Rayleigh channel and are not sensitive to different propagation scenarios. The authors' study of the array height and element polarisation revealed that they mainly impact the subchannels' power, which leads to offering different MIMO channel capacities. They also observed that in spite of geometrical dissimilarities between underground mines and large tunnels, some of their measurement results in the mine are similar to those of subway tunnels obtained by previous studies.