Resonant nanoelectromechanical systems (NEMS) are being actively investigated as sensitive mass detectors for applications such as chemical and biological sensing. We demonstrate that highly uniform arrays of nanomechanical resonators can be used to detect the binding of individual DNA molecules through resonant frequency shifts resulting from the added mass of bound analyte. Localized binding sites created with gold nanodots create a calibrated response with sufficient sensitivity and accuracy to count small numbers of bound molecules. The amount of nonspecifically bound material from solution, a fundamental issue in any ultra-sensitive assay, was measured to be less than the mass of one DNA molecule, allowing us to detect a single 1587 bp DNA molecule.

Abstract-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 discussed as are experimental results demonstrating the onset of limit cycle oscillations as continuous wave (CW) laser power is increased. A model describing the motion and heating of the devices is derived and analyzed. Conditions for the onset of limit cycle oscillations are computed as are conditions for these oscillations to be either hysteretic or nonhysteretic. An example simulation of a particular device is discussed and compared with experimental results.[1190]Index Terms-Finite element method (FEM), laser drive, limit cycle oscillation, self-oscillation, thermal stress.

We report a method of optical excitation of nanomechanical cantilever-type oscillators. The periodic driving signal with a controlled modulation amplitude was provided by a 415 nm diode laser, wherein the laser spot was located at some distance away from the clamped end of the cantilever. The measured resonant response of the cantilever was obtained at distances in excess of 160μm with varying oscillator dimensions. The effectiveness of the driving mode is studied for different combinations of materials, namely Si–SiO2 and Si3N4–SiO2. These observations were considered within the theoretical framework of the mechanism of heat transfer. We show that measurable amplitudes of vibrations can be obtained at temperature changes much less than 1°.

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 that the entrainment zone is hysteretic and can be as wide as 4% of the natural frequency of the resonator, 400 times the 1/Q ϳ10 Ϫ4 half-width of the resonant peak. Possible applications are discussed based on the wide range of frequency tuning and the power gain provided by the large amplitude of self-oscillations ͑controlled by a small pilot signal͒.