Summary One of the main obstacles to including transient dynamic effects into the performance functions of a structural optimization is the high computational cost of each time-dependent simulation. The focus of this paper is on the application of model order reduction techniques to reduce the transient analysis time for the attainable optimization process. The software mor4ansys developed at IMTEK performs model reduction via the Arnoldi algorithm directly to ANSYS finite element models. We adopt a micro accelerometer as an example to demonstrate the advantages of this approach. The harmonic and transient results of a reduced model of the accelerometer yield very good agreement with those from the original high dimensional ANSYS model. The use of model reduction within the optimization iterations produces almost the same results as without order reduction and speeds up the total computation by about an order of magnitude.

No published data are available about the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and the role of PPARgamma in retinoblastoma protein (RB)-deficient human colorectal cancer (CRC) cells (SNU-C4 and SNU-C2A). Our aim was to investigate whether PPARgamma is expressed in SNU-C4 and SNU-C2A cells and to elucidate possible molecular mechanisms underlying the effect of pioglitazone, a synthetic ligand for PPARgamma, on cell growth in these cell lines. RT-PCR and Western blot analysis showed that both human CRC cell lines expressed PPARgamma mRNA and protein. Pioglitazone inhibited the cell growth of both cell lines through G2/M phase block and apoptosis. In addition, pioglitazone caused a down-regulation of the X chromosome-linked inhibitor of apoptosis (XIAP), Bcl-2, and cyclooxygenase-2 (COX-2) under conditions leading to PPARgamma down-regulation. These results suggest that pioglitazone may have therapeutic relevance or significance in the treatment of human CRC, and the down-regulation of XIAP, Bcl-2, and COX-2 may contribute to pioglitazone-induced apoptosis in these and other RB-deficient cell lines and tumors.

In this paper we present an in-depth parametric study and structural optimization for a micro-optical switch based on the concept of a laterally driven electromagnetic microactuator (LaDEM). This utilizes the nonlinear behavior of a snap-through buckling occurring in two arch-shaped leaf springs of the switch, when actuated by a distributed Lorentz force induced along the leaf springs. A sudden jump in displacement can facilitate a large actuation stroke suitable for practical applications. The leaf springs are connected to the fixed frame with two meandering parts, which also enhance their flexibility. Thus, an important objective in the design of the micro-optical switch is to achieve a large displacement with low actuation force. For this purpose, the effect of important geometrical parameters, such as the initial height of the leaf spring and the dimensions of meandering part on the displacement response is first investigated and optimized to satisfy given design specifications. The nonlinear displacement–load response calculated by a modified Riks method in ABAQUS shows good agreement with the measurement result. Nonlinear finite element techniques and optimizations are found to be valuable tools for the analysis and design of microactuators, which utilize a complex nonlinear snap-through buckling behavior.

A robust optimal design of shape and size is formulated for vibratory microgyroscopes that can reduce the effect of variations from uncertainties in microelectromechanical systems fabrication. The important objective in the design of vibratory microgyroscopes is to reduce the difference between the resonance frequencies of the vertical (detecting) and lateral (driving) modes in order to attain high mechanical detecting sensitivity. The deterministic optimization for this goal results in good performance but is sensitive to fabrication errors. The basic idea of the present formulation is to obtain robustness of the objective function by minimizing the gradient of the objective function with respect to uncertain variables through a proper selection of shapes and sizes. The beam width, length and thickness of vibratory microgyroscopes are adopted as design variables and are simultaneously regarded as uncertain variables in the optimization problems. A robustness check using a newly defined yield through the Monte Carlo simulation has shown that the robust optimal design obtained has generated twice the number of acceptable designs than the deterministic optimum. The important point is that the formulation of minimizing the maximum sensitivity of the objective function requires no statistical information on the uncertainties and yet achieves robustness.

This paper demonstrates a novel quadstable monolithic mechanism (QsMM), which provides four stable equilibrium positions within its planar operation range. The QsMM has been realized from the use of both X- and Y-directional bistable structures, which utilize curved snapping beams. Two pairs of curved beams were attached to an inner frame in both X and Y directions to present an independent bistable behavior in the directions. It was found out that the design of the inner frame is crucial for the quadstability and dynamic responses of the mechanism. A millimeter-scale brass mechanism was actually fabricated by ultraprecision milling to test the quadstability and the force-displacement behavior. The prototype clearly demonstrates four distinct stable positions in its millimeter-scale operation range. The design concept, finite element simulation, fabrication, and experimental measurement of the proposed multistable mechanism have been presented. The mechanical multistability of the proposed QsMM can be utilized for multiple switching and optical networking applications, yielding low power consumption operations.

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This paper discusses optimization of an electromagnetic microactuator for large-displacement optical switching. The microactuator used in this research is a laterally driven electromagnetic one that provides parallel actuation to the silicon substrate surface (in-plane motion) using the Lorentz force. When the microactuator is driven by the distributed Lorentz force induced along the arch-shaped leaf springs, a buckling phenomenon in two leaf springs enables a large displacement with a relatively small actuation load. An important design objective of a microactuator is to achieve a large displacement with a low actuating force. In this research, two optimization formulations have been performed to improve the displacement capabilities of the microactuator. In the first, the actuation load to obtain a specific displacement is minimized, subject to constraints on the first natural frequency and maximum allowable stress. In the second, the actuation displacement for a given actuation load is maximized, subject to the same constraints as in the first formulation. These optimizations have generated considerably improved designs, making the actuators capable of large-displacement actuations with small actuating loads.

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