Abstract
U-shape nanoelectromechanical systems (NEMS) are potential for developing miniature sensors. While the electro-mechanical performance of conventional beam-type NEMS has been exclusively addressed in the literature, few works have considered this phenomenon in U-shaped systems. Herein, the static and dynamic pull-in instability of the U-shaped NEMS is investigated under the presence of vdW force. Based on the recently developed consistent couple stress theory (CCST), the size-dependent constitutive equation is derived. Two types of the beam cross-sections including rectangular and circular geometries are considered. The nonlinear equations are solved by employing Ray-leigh-Ritz solution method. The developed model is validated by comparison with the results presented in literature. The effect of various parameters on the static and dynamic pull-in parameters, phase plans and stability threshold of the system is discussed. The obtained results reveal that the vdW attraction decreases the pull-in voltage while the size dependency enhances the instability voltage. On the other hand, the presented model demonstrates that characteristics of the tip-plate can change the pull-in parameters significantly.
Highlights
A true understanding of the electromechanical stable behavior of nanoelectromechanical systems (NEMS) is crucial for reliable design, fabrication and operation of these devices
The U-shaped NEMS are made of two parallel cantilever micro/nano-beams with a rigid plate attached to theirs free ends
The U-shaped MEMS/NEMS are used for developing new generation of miniature sensors, actuators and switches [7,8,9,10]
Summary
A true understanding of the electromechanical stable behavior of NEMS is crucial for reliable design, fabrication and operation of these devices. The U-shaped actuator for capacitive applications with adjustable tuning range is studied by Yan and coworkers [8] They showed that U-shaped structures provide enhanced electrical performance. It is well proved that the presence of vdW force substantially affects the pull-in instability of NEMS at the nano-scale separations. This size-dependency of material characteristics, i.e. size effect, cannot be modeled via classic continuum mechanics. The effect of vdW force is incorporated in theoretical modeling of the U-shaped NEMS. Besides the vdW force, the size effect is another crucial small-scale phenomenon that might affect the performance of NEMS, should be incorporated in theoretical models. The Rayleigh-Ritz method (RRM) is applied to solve the obtained equations
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