Microactuators are one of the key components in MEMS technology, and various designs have been realized through different fabrication processes. One type of microactuator commonly used is the scratch drive actuator (SDA) that is frequently fabricated by surface micromachining processes. An experimental investigation has been conducted on the force characteristics of SDAs fabricated using the JDSU Microsystems MUMPs process. One-, two-, three-and four-plate SDAs connected to box-springs have been designed and fabricated for these experiments using MUMPs run 44. The spring constant for the box-springs has been calculated by FEM using ANSYS software. The product of the spring constant and spring extension is used to measure the forces produced by these SDAs. It is estimated that the forces produced exceed 250 µN from a one-plate SDA and 850 µN from a four-plate SDA.

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A microelectromechanical systems (MEMS)-based structure capable of operating mechanically as a directional acoustical sensor is presented. The structure, fabricated through the commercially available SOIMUMPS foundry process, consists of two circular discs attached to a central suspension beam, fixed at both ends. The design of the structure resembles other directional MEMS microphones that mimic the directional hearing organ of the parasitoid fly, Ormia ochracea. Modal analysis and mechanical acoustic directionality analysis using both laser Doppler vibrometry and finite element modelling have been implemented. It is demonstrated that this coupled MEMS structure exhibits an acoustic directional response, with a one-to-one relationship between the relative vibration amplitudes of the two coupled discs and the angle of sound, from −75° to +60°

The scratch drive actuator (SDA) is a key element in microelectromechanical-system (MEMS) technology. This type of actuator can be designed to travel over very long distances with precise step sizes. The MEMS designer requires models of the SDA to incorporate these devices into their microsystem applications. Models are developed for the SDA in its working state, building on previous work reported in the literature. A suspended SDA plate actuated by electrostatic forces has been analysed. A mathematical model has been established based on electrostatic coupled mechanical theory. Two SDA modes have been analysed namely the noncontact mode and the contact mode. The noncontact mode allows the designer to establish the threshold voltage after which the actuator plate snaps down. For the contact mode, the relationship between applied voltage and contact length is first obtained. Subsequently, the geometrical model of a bent plate is used to determine the relationship between contact distance and step size. These two results are then combined to obtain the value of actuator step size against applied voltage. A coupled-field electromechanical simulation of the microactuators has been performed using the commercially available software tool, IntelliSuite. On the experimental front, a Veeco NT1000 surface profiling tool has been used to measure the bending of the SDA plate. The results obtained from modelling, simulation and experimentation are compared

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An extensive series of vibration and acoustic measurements has been conducted on a large (63 inch diameter three-vane impeller) centrifugal wastewater pump at a municipal pump station. Vibration measurements on the pump bearing housing exceeded the design specification at most operating blade-passing frequencies (BPF). The purpose of the testing was to determine the primary mechanisms of the vibration, including contributions from an acoustic resonance (within the piping system) and the pump’s hydrodynamic near-field. In Part 1, the physical mechanisms of pump vibration and overall experimental results are presented.

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