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Synchronized micromechanical oscillators have potential for applications in signal processing, neural computing, sensing, and other fields. This paper explores the conditions under which coupled nonlinear limit cycle microoscillators can synchronize. As an example of the modeling approach and to be able to obtain results for a system that has been experimentally realized, thermally excited dome oscillators, which are fabricated by buckling of a thin circular film of polysilicon, are modeled. Starting with the von Karman plate equations and an assumed mode shape, a Galerkin projection is performed to obtain an ordinary differential equation for the postbuckled dynamics of the mode. Because the structure is thermally excited, a thermal model is built by solving the heat equation on a disk with appropriate boundary conditions. Bifurcation analysis of the single oscillator model is performed to look for basic underlying phenomena. Conditions under which two slightly detuned coupled limit cycle dome oscillators will synchronize are explored. [2007-0208] Index Terms--Buckling, coupled oscillators, Galerkin projections, resonators, thermomechanical modeling.

Thin, planar, radio frequency microelectromechanical systems (MEMS) resonators have been shown to self-oscillate in the absence of external forcing when illuminated by a direct current (dc) laser of sufficient amplitude. In the presence of external forcing of sufficient strength and close enough in frequency to that of the unforced oscillation, the device will become frequency locked, or entrained, by the forcing. In other words, it will vibrate at the frequency of the external forcing. Experimental results demonstrating entrainment for a disk-shaped oscillator under optical and mechanical excitation are reviewed. A thermomechanical model of the system is developed and its predictions explored to explain and predict the entrainment phenomenon. The validity of the model is demonstrated by the good agreement between the predicted and experimental results. The model equations could also be used to analyze MEMS limit-cycle oscillators designed to achieve specific performance objectives.

We fabricated a microfluidic flow meter and measured its response to fluid flow in a microfluidic channel. The flow meter consisted of a micromechanical plate, coupled to a laser deflection system to measure the deflection of the plate during fluid flow. The 100 [micro]m square plate was clamped on three sides and elevated 3 [micro]m above the bottom surface of the channel. The response of the flow meter was measured for flow rates, ranging from 2.1 to 41.7 [micro]L/min. Several fluids, with dynamic viscosities ranging from 0.8 to 4.5 x [10.sup.-3] N/m, were flowed through the channels. Flow was established in the microfluidic channel by means of a syringe pump, and the angular deflection of the plate monitored. The response of the plate to flow of a fluid with a viscosity of 4.5 x [10.sup.-3] N/m was linear for all flow rates, while the plate responded linearly to flow rates less than 4.2 [micro]L/min of solutions with lower dynamic viscosities. The sensitivity of the deflection of the plate to fluid flow was 12.5 [+ or -] 0.2 [micro]rad/ ([micro]L/min), for a fluid with a viscosity of 4.5 x [10.sup.-3] N/m. The encapsulated plate provided local flow information along the length of a microfluidic channel. [1159]

Advanced finite element software makes it possible to perform accurate simulations of orthogonal metal cutting provided all input parameters such as material properties, friction and material separation criteria are known. In principle, such properties can be determined by performing a series of cutting experiments and mechanical property tests, and then iterating the finite element simulations until acceptable agreement is reached. Cutting measurements have generally included only cutting forces and tool-chip temperatures. We hypothesize that by closely coupling simulations to conventional cutting force measurements and with fine scale spatial and temporal experimental measurements of temperature and strain fields, questions related to the choice of parameters in finite element simulations can be resolved. As a step towards that resolution a method for high resolution experimental measurements of temperature and strain fields is presented here. Temperatures of the workpiece and chip are measured during transient metal cutting over areas of 27X27 [micro]m and time scales of 200 ns by using infrared detectors. Three different materials, 1018CR steel, Al6061-T6 and Ti-6Al-4V are tested. A grid method is used to measure deformations in steel with a spatial resolution of 50 [micro]m.

Dfield and Pplane are two excellent programs for graphing differential equations with the statistical/mathematical software MatLab. Both programs are accessible as function files on ftp.mathworks. They do not require proficiency at MatLab, but they can help students learn to use MatLab. They also help students learn first order differential equations, or systems of equations. Students no longer need to write programs to study these topics with computer graphics.

A coverlayer of Kapton provides a higher fatigue life for rolled-annealed copper cables than that of cables lacking the coverlayer. The fatigue life increases with bond strength among adhesive and copper layers. The debond length decreases and the bridging stiffness increases. Also, there is reduction in stress intensity factor and fatigue crack growth. Description of a fracture mechanics model for the analysis of fatigue failure of copper-Kapton flex cables is given.

Previous experiments have shown a link between oxidation and strength changes in single crystal silicon nanostructures but provided no clues as to the mechanisms leading to this relationship. Using atomic force microscope-based fracture strength experiments, molecular dynamics modeling, and measurement of oxide development with angle resolved x-ray spectroscopy we study the evolution of strength of silicon (111) surfaces as they oxidize and with fully developed oxide layers. We find that strength drops with partial oxidation but recovers when a fully developed oxide is formed and that surfaces intentionally oxidized from the start maintain their high initial strengths. MD simulations show that strength decreases with the height of atomic layer steps on the surface. These results are corroborated by a completely separate line of testing using micro-scale, polysilicon devices, and the slack chain method in which strength recovers over a long period of exposure to the atmosphere. Combining our results with insights from prior experiments we conclude that previously described strength decrease is a result of oxidation induced roughening of an initially flat silicon (1 1 1) surface and that this effect is transient, a result consistent with the observation that surfaces flatten upon full oxidation. [ABSTRACT FROM AUTHOR]