N. Shukla and A. Saigal
Nanomechanical antenna beam, natural frequency, finite element analysis, modal analysis, harmonic analysis Nomenclature E Modulus of elasticity I Moment of inertia L Length T Temperature UT hermal Thermal energy UV ibration Vibrational energy b Width f Frequency h Thickness m Mass me Effective mass k Stiffness ke Effective stiffness t Time ∗ Department of Mechanical Engineering, Virginia Tech, Blacks- burg, VA 24061; e-mail: [email protected] ∗∗ Department of Mechanical Engineering, T
This paper investigates different ways to increase and detect high modal frequencies. Our approach is to explore new structural geome- tries and materials that give rise to easily detectable displacements. A 10.7 μm long suspended silicon-based antenna beam with 20 pads on each side gives rise to a typical large displacement mode shape at resonant frequency of 545.7 MHz. This typical mode, henceforth known as collective mode, can be detected by magnetomotive tech- nique. The numerical simulations predict higher collective mode frequencies for materials having higher (E/ρ) ratios. We also find that frequency increases considerably if the length of the side pads is reduced. Other geometrical changes such as using single sideway pads on both sides of central beam or varying pad widths may result in high collective mode frequencies. Harmonic analysis predicts that higher collective modes can also be detected as they have net sweep area of the same order as the 1st collective mode.
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