J.-M. Huang

Bio: J.-M. Huang is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Surface micromachining & Capacitive sensing. The author has an hindex of 3, co-authored 3 publications receiving 339 citations. Previous affiliations of J.-M. Huang include Beijing University of Posts and Telecommunications.

Mechanical design and optimization of capacitive micromachined switch

Abstract: Design and optimization of a shunt capacitive micromachined switch is presented. The micromachined switch consists of a thin metal membrane called the “bridge” suspended over a center conductor, and fixed at both ends to the ground conductors of a coplanar waveguide (CPW) line. A static electromechanical model considering the residual stress effects is developed to predict the effective stiffness constant and the critical collapse voltage of the bridge for several typical bridge geometries. The deformation of the bridge and its contact behavior with the dielectric layer are analyzed using the finite element method (FEM) in order to explore a good contact field with different bridge geometries. Furthermore, a nonlinear dynamic model that captures the effects of electrostatic forces, elastic deformation, residual stress, inertia, and squeeze film damping is developed, and is used for predicting the switching speed (including the switching-down and the switching-up time) and the Q -factor. The effects of variation of important parameters on the mechanical performance have been studied in detail, and the results are expected to be useful in the design of optimum shunt capacitive micromachined switch. The results may also be useful in the design of actuators with membranes or bridges.

An approach to the coupling effect between torsion and bending for electrostatic torsional micromirrors

Abstract: A general theoretical model using the coupling effect between the torsion and bending is presented in this paper, which characterizes the static properties of the electrostatic torsional micromirror, especially its pull-in effect. A set of normalized equations governing the static actuation properties of the torsional micromirror based on the parallel plate capacitor model is derived to demonstrate the relationships between the parameters of static characteristics, such as torsion angle, vertical displacement, and applied voltage. Thereafter, the pull-in effect is investigated specifically to predict pull-in voltage, pull-in angle, and pull-in displacement, which highly depend on the electrode size and position, and ratio of the bending and torsion effect of the torsion beam. The ratio of the bending and torsion effect plays a key role in the pull-in phenomena. It also determines the instability mode of torsional micromirrors dominated by either the torsion or bending effect. Then, a group of torsional micromirrors is fabricated using three-layer-polysilicon micromachining process and measured using an optical projection method to verify the static actuation relation and pull-in effect respectively. The experimental data are processed and analyzed, and the theoretical analysis is in good agreement with the experimental results.

Mechanical characterization of micromachined capacitive switches: design consideration and experimental verification

Abstract: The mechanical modeling and experimental study of radio frequency (RF) micromachined capacitive switches is presented in this paper. The micromachined capacitive switch, fabricated using bulk and surface micromachining techniques, consists of a thin metal membrane suspended over a center conductor, and fixed at both ends to the ground conductors of a coplanar waveguide (CPW) line. A static mechanical model considering complicated geometry and the residual stress effect of the bridge is established to demonstrate the pull-in instability phenomenon of the micromachined capacitive switch, and to predict the effective stiffness constant and critical collapse voltage of the bridge for several typical bridge geometries. An optoelectronic laser interferometric system, based on a modified Michelson interferometer incorporated with optoelectronic devices is developed to evaluate the membrane deformation characteristics of the micromachined capacitive switch with different applied dc bias voltages. It is illustrated that the analytical solution is well agreed with the numerical simulation and experiment.

Electrostatic pull-in instability in MEMS/NEMS: A review

Abstract: Pull-in instability as an inherently nonlinear and crucial effect continues to become increasingly important for the design of electrostatic MEMS and NEMS devices and ever more interesting scientifically. This review reports not only the overview of the pull-in phenomenon in electrostatically actuated MEMS and NEMS devices, but also the physical principles that have enabled fundamental insights into the pull-in instability as well as pull-in induced failures. Pull-in governing equations and conditions to characterize and predict the static, dynamic and resonant pull-in behaviors are summarized. Specifically, we have described and discussed on various state-of-the-art approaches for extending the travel range, controlling the pull-in instability and further enhancing the performance of MEMS and NEMS devices with electrostatic actuation and sensing. A number of recent activities and achievements methods for control of torsional electrostatic micromirrors are introduced. The on-going development in pull-in applications that are being used to develop a fundamental understanding of pull-in instability from negative to positive influences is included and highlighted. Future research trends and challenges are further outlined.

RF MEMS and their applications

Abstract: Preface. Microelectromechanical Systems (MEMS) and Radio Frequency MEMS. MEMS Materials and Fabrication Techniques. RF MEMS Switches and Micro Relays. MEMS Inductors and Capacitors. Micromachined RF Filters. Micromachined Phase Shifters. Micromachined Transmission Lines and Components. Micromachined Antennae. Integration and Packaging for RF MEMS Devices. Index.

A closed-form model for the pull-in voltage of electrostatically actuated cantilever beams

Abstract: A simple computationally efficient closed-form model has been developed to determine the pull-in voltage of a cantilever beam actuated by electrostatic force. The approach is based on a linearized uniform approximate model of the nonlinear electrostatic pressure and the load deflection model of a cantilever beam under uniform pressure. The linearized electrostatic pressure includes the electrostatic pressure due to the fringing field capacitances and has been derived from Meijs and Fokkema's highly accurate empirical expression for the capacitance of a VLSI on-chip interconnect. The model has been verified by comparing the results with published experimentally verified 3D finite element analysis results and also with results from similar closed-form models. The new model can evaluate the pull-in voltage for a cantilever beam with a maximum deviation of ±2% from the finite element analysis results for wide beams, and a maximum deviation of ±1% for narrow beams (extreme fringing field).