Artificial superhydrophobic surfaces are typically fabricated by tuning the surface roughness of intrinsically hydrophobic surfaces. We report here the design and fabrication of micro-textures for inducing a superhydrophobic behavior on hydrogen-terminated Si surfaces with an intrinsic water contact angle of approximately 74 degrees . The micro-textures consist of overhang structures with well-defined geometries fabricated by microfabrication technologies, which provide positions to support the liquid and prevent the liquid from entering into the indents between the micro-textures. As a result, water is in contact with a composite surface of solid and air, which induces the observed macroscopic superhydrophobic behavior.

We have utilized soft lithography techniques to create three-dimensional arrays of blood microchannels and gas pathways in poly(dimethylsiloxane) (PDMS) that approach the microvascular scale of the natural lung. The blood microchannels were lined with endothelial cells in an effort to provide a non-thrombogenic surface that might ultimately reduce the need for systemic anticoagulation. A novel design and fabrication method were developed to create prototype modules for gas permeance and cell culture testing. The gas permeance modules contained 6 layers, four gas and two blood, while the modules for cell culture testing contained two layers of blood channels. The gas permeance of the modules was examined and maximum values of 9.16 x 10(-6) and 3.55 x 10(-5) mL/s/cm(2)/cmHg, for O(2) and CO(2) respectively, were obtained. Finally, endothelial cells were seeded and dynamically cultured in prototype cell culture modules. Confluent and viable cell monolayers were achieved after 10 days of perfusion.

Thin film materials are normally under residual stresses as a result of fabrication processes. Unlike microelectronics devices, a micromechanical structure is no longer constrained by its underlying silicon substrate after anisotropic etch undercutting; therefore, residual stresses may result in the bending and buckling of a micromechanical structure. The buckling behavior has been exploited to measure the residual stresses of thin films. This characteristic can also be applied to fabricate out-of-plane three-dimensional micromechanical structures if their deflections are controllable. The buckling of a microbridge is difficult to predict since it is strongly dominated by its fabrication processes and boundary conditions. Currently the information regarding the buckling of micromachined structures is still not complete. The application of the buckling behavior is therefore limited. In this research, the effects of boundary conditions and gradient residual stresses on the buckling behavior of microbridges were studied using analytical and experimental approaches. The variations of the buckling amplitude orientations with the thickness and length of the microbridges were obtained; therefore, the buckling behavior can be predicted and then exploited to fabricate useful micromechanical structures. The potential application of this research lies in preventing the leakage of the microvalves.

The use of an interdigitated electrode configuration for tunable MEMS resonators is investigated. The tuning concept utilizes a shunt capacitor concept based on the fact that the mechanical compliance (stiffness) of the system is a function of both the mechanical properties and the electromechanical coupling of the piezoelectric element. Since the electromechanical coupling is dependant on the electrical impedance of the piezoelectric element and its shunt circuit, the circuit conditions applied to the piezoelectric tuning element can be varied in such a way as to tune the vibrational frequency of the resonator [1]. By utilizing an interdigitated electrode design to elicit the d33 response of the piezoelectric, a greater electromechanical coupling is achievable, corresponding to a wider range of tunability. In this paper, a model of the resonator is presented and then used in a study to determine the parameters which result in the highest range of tunability for the resonator.

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