Response of parametrically-driven nonlinear coupled oscillators with application to micro- and nanomechanical resonator arrays

The response of a coupled array of nonlinear oscillators to parametric excitation is calculated in the weak nonlinear limit using secular perturbation theory. Exact results for small arrays of oscillators are used to guide the analysis of the numerical integration of the model equations of motion for large arrays. The results provide a qualitative explanation for a recent experiment [Buks and Roukes, cond-mat/0008211, to appear in J. MEMS (2002)] involving a parametrically-excited micromechanical resonator array. Future experiments are suggested that could provide quantitative tests of the theoretical predictions.Comment: 27 pages (in preprint format), 8 figure

Observation of Locked Intrinsic Localized Vibrational Modes in a Micromechanical Oscillator Array

金沢大学理学部The nonlinear vibrational properties of a periodic micromechanical oscillator array have been measured. For sufficiently large amplitude of the driver, the optic mode of the di-element cantilever array becomes unstable and breaks up into excitations ranging over only a few cells. A driver-induced locking effect is observed to eternalize some of these intrinsic localized modes so that their amplitudes become fixed and the modes become spatially pinned

Study of intrinsic localized vibrational modes in micromechanical oscillator arrays

金沢大学大学院自然科学研究科物理学金沢大学理学部Intrinsic localized modes (ILMs) have been observed in micromechanical cantilever arrays, and their creation, locking, interaction, and relaxation dynamics in the presence of a driver have been studied. The micromechanical array is fabricated in a 300 nm thick silicon-nitride film on a silicon substrate, and consists of up to 248 cantilevers of two alternating lengths. To observe the ILMs in this experimental system a line-shaped laser beam is focused on the 1D cantilever array, and the reflected beam is captured with a fast charge coupled device camera. The array is driven near its highest frequency mode with a piezoelectric transducer. Numerical simulations of the nonlinear Klein-Gordon lattice have been carried out to assist with the detailed interpretation of the experimental results. These include pinning and locking of the ILMs when the driver is on, collisions between ILMs, low frequency excitation modes of the locked ILMs and their relaxation behavior after the driver is turned off. © 2003 American Institute of Physics

Viral nanomotors for packaging of dsDNA and dsRNA

While capsid proteins are assembled around single-stranded genomic DNA or RNA in rod-shaped viruses, the lengthy double-stranded genome of other viruses is packaged forcefully within a preformed protein shell. This entropically unfavourable DNA or RNA packaging is accomplished by an ATP-driven viral nanomotor, which is mainly composed of two components, the oligomerized channel and the packaging enzymes. This intriguing DNA or RNA packaging process has provoked interest among virologists, bacteriologists, biochemists, biophysicists, chemists, structural biologists and computational scientists alike, especially those interested in nanotechnology, nanomedicine, AAA+ family proteins, energy conversion, cell membrane transport, DNA or RNA replication and antiviral therapy. This review mainly focuses on the motors of double-stranded DNA viruses, but double-stranded RNA viral motors are also discussed due to interesting similarities. The novel and ingenious configuration of these nanomotors has inspired the development of biomimetics for nanodevices. Advances in structural and functional studies have increased our understanding of the molecular basis of biological movement to the point where we can begin thinking about possible applications of the viral DNA packaging motor in nanotechnology and medical applications

Optical properties of square lattices of gold nanoparticles

We reanalyse optical measurements on two-dimensional lattices of ultrafine gold particles, produced by electron beam lithography. The spectra exhibit a distinct absorption peak due to the localized plasma resonance of the conduction electrons in the particles. The theoretical modeling used rigorous solutions, in the long-wavelength limit, for the polarizability of oblate spheroids and truncated spheres on a substrate. The dipole-dipole interactions between the particles in the square lattice were taken into account. We find good agreement between experimental and theoretical absorption peak positions for the case of oblate spheroids, but not for truncated spheres. Peak widths and minimum transmittances also show satisfactory agreement with theory

Optical properties of square lattices of gold nanoparticles

We reanalyse optical measurements on two-dimensional lattices of ultrafine gold particles, produced by electron beam lithography. The spectra exhibit a distinct absorption peak due to the localized plasma resonance of the conduction electrons in the particles. The theoretical modeling used rigorous solutions, in the long-wavelength limit, for the polarizability of oblate spheroids and truncated spheres on a substrate. The dipole-dipole interactions between the particles in the square lattice were taken into account. We find good agreement between experimental and theoretical absorption peak positions for the case of oblate spheroids, but not for truncated spheres. Peak widths and minimum transmittances also show satisfactory agreement with theory

Conformation, Length, and Speed Measurements of Electrodynamically Stretched DNA in Nanochannels

A method is presented to rapidly and precisely measure the conformation, length, speed, and fluorescence intensity of single DNA molecules constrained by a nanochannel. DNA molecules were driven electrophoretically from a nanoslit into a nanochannel to confine and dynamically elongate them beyond their equilibrium length for repeated detection via laser-induced fluorescence spectroscopy. A single-molecule analysis algorithm was developed to analytically model bursts of fluorescence and determine the folding conformation of each stretched molecule. This technique achieved a molecular length resolution of 114 nm and an analysis time of around 20 ms per molecule, which enabled the sensitive investigation of several aspects of the physical behavior of DNA in a nanochannel. λ-bacteriophage DNA was used to study the dependence of stretching on the applied device bias, the effect of conformation on speed, and the amount of DNA fragmentation in the device. A mixture of λ-bacteriophage with the fragments of its own HindIII digest, a standard DNA ladder, was sized by length as well as by fluorescence intensity, which also allowed the characterization of DNA speed in a nanochannel as a function of length over two and a half orders of magnitude