Alan T. Zehnder

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— Limit cycle, or self oscillations can occur in a variety of NEMS devices illuminated within an interference field. As the device moves within the field, the quantity of light absorbed and hence the resulting thermal stresses changes, resulting in a feedback loop that can lead to limit cycle oscillations. Examples of devices that exhibit such behavior are(More)
Self-sustained mechanical vibrations of a disc-type micro-fabricated resonator were experimentally observed when a continuous wave (CW) laser beam was focused on the periphery of the disc (for a 40 µm diameter resonator, natural frequency 0.89MHz, the laser power above a 250 W threshold was required). A theoretical model for self-oscillatory behavior has(More)
We demonstrate synchronization of laser-induced self-sustained vibrations of radio-frequency micromechanical resonators by applying a small pilot signal either as an inertial drive at the natural frequency of the resonator or by modulating the stiffness of the oscillator at double the natural frequency. By sweeping the pilot signal frequency, we demonstrate(More)
—Thin, planar, radio frequency microelectromechan-ical 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(More)
Moisture diffusion properties of the polyimide HFPE-II-52 were determined using weight gain, weight loss and swelling experiments over a temperature range of 25 0 C to 200 0 C. Below100 0 C, diffusivity was measured using standard weight loss and weight gain methods. Above 100 ° C, diffusivity is found by weight loss experiments performed by placing(More)
Optically actuated Radio Frequency MEMS devices are seen to self oscillate or vibrate under illumination of sufficient strength [1]. These oscillations can be frequency locked to a periodic forcing, applied through an inertial drive at the forcing frequency, or subharmonically via a parametric drive, hence providing tunability. In a previous work [2] this(More)
An emerging change across the science, technology, engineering, and mathematics curriculum is the implementation of online, or virtual laboratories as supplements or replacements to both homework assignments and laboratory exercises. To test the effectiveness of such labs, a web-based virtual laboratory on the topic of torsion of engineered and biological(More)
The transformation of 3-chlorobenzoate (3CB) and acetate at initial concentrations in the wide range of 10 nM to 16 mM was studied in batch experiments with Pseudomonas sp. strain B13. Transformation rates of 3CB at millimolar concentrations could be described by Michaelis-Menten kinetics (K(infm), 0.13 mM; V(infmax), 24 nmol (middot) mg of protein(sup-1)(More)
We study the dynamics of a thermo-mechanical model for a forced disc shaped, micromechanical limit cycle oscillator. The forcing can be accomplished either parametrically, by modulating the laser beam incident on the oscillator, or non-parametrically, using inertial driving. The system exhibits both 2:1 and 1:1 resonances, as well as quasiperiodic motions(More)
Keywords: MEMS Finite element method Resonator Dynamical systems Limit cycle Hopf a b s t r a c t A micro-scale resonator suspended over a substrate and illuminated with a continuous wave (CW) laser forms an interferometer which couples deflection of the resonator to light absorption. In turn, absorption creates temperature and thermal stress fields which(More)