Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices.

Silver nanoparticles (NPs) are installed into a porphyrinic zirconium-based metal−organic framework (Zr-MOF), NU-902, through a postsynthetic modification followed by an ion-exchange process. Both the framework-immobilized Ag(I) ions and partially reduced silver NPs confined within the nanopores of NU-902 with the size of around 3 nm are found in the obtained composite. As both the silver NPs and porphyrinic linkers of NU-902 are electrocatalysts for the oxidation of nitrite, the obtained nanocomposite can be applied for the electrochemical nitrite sensor, and the resulting sensing performance is significantly better than that of the pristine porphyrinic Zr-MOF.

Alloys with ultra-high strength and sufficient ductility are highly desired for modern engineering applications but difficult to develop. Here we report that, by a careful controlling alloy composition, thermomechanical process, and microstructural feature, a Co-Cr-Ni-based medium-entropy alloy (MEA) with a dual heterogeneous structure of both matrix and precipitates can be designed to provide an ultra-high tensile strength of 2.2 GPa and uniform elongation of 13% at ambient temperature, properties that are much improved over their counterparts without the heterogeneous structure. Electron microscopy characterizations reveal that the dual heterogeneous structures are composed of a heterogeneous matrix with both coarse grains (10∼30 μm) and ultra-fine grains (0.5∼2 μm), together with heterogeneous L12-structured nanoprecipitates ranging from several to hundreds of nanometers. The heterogeneous L12 nanoprecipitates are fully coherent with the matrix, minimizing the elastic misfit strain of interfaces, relieving the stress concentration during deformation, and playing an active role in enhanced ductility.

This paper derives an approximate analytical solution to the pull-in voltage of a micro bridge with elastic boundaries. The analytical model considers the elastic boundary effect, fringing field capacitance, residual stresses and the distributed flexibility of the bridge. The accuracy of the present approximate analytical solution is verified by comparison with the simulation results of commercial FEM packages and other published closed-form solutions as well as experimental measured data. The deviation of the present approximate analytical solution is within 5% for a wide beam and a narrow beam in a small deflection regime. The present approximate analytical solution has explicit physical meaning and is highly accurate for device design.

This paper presents a fringe capacitance formula of microstructures. The formula is derived by curve fitting on ANSYS simulation results. Compared with the ANSYS and experimental results, the deviation is within ± 2%. The application to determine the pull-in voltage of an electrostatic micro-beam is demonstrated, which agrees very well with the experimental data. The formula presented is very accurate, yields explicit physical meanings and is applicable to common dimension ranges for MEMS devices.