Effect of non-ideal clamping shape on the resonance frequencies of silicon nanocantilevers

Frequency equation and semi-empirical mechanical coupling strength of microcantilevers in an array

A characteristic equation for the frequencies of the T-shaped and overhang-shaped cantilevers is derived for the first time. We show that there are optimum values of the overhang lengths and widths that maximize the frequency and the number of maxima is corresponding to the mode number. The frequency of higher-order modes could be tuned by changing the overhang dimensions. Especially, a semi-empirical formula for the coupling strength κ $$ \left(\kappa \right) $$ between cantilevers in an array is proposed where the strength presents a cubic decrease with the overhang width ξ $$ \left(\xi \right) $$ and a linear increase with the overhang length η $$ \left(\eta \right) $$ , κ = η / ξ 3 $$ \kappa =\eta /{\xi}^3 $$ . There is a very good agreement between the proposed formula and the values obtained in recent experiments by other researchers.

Temperature dependent Young's modulus of ZnO nanowires

A thermal resonant method was developed to accurately determine the temperature-dependent Young's moduli of nanowires. In this method, the frequency spectra of a [0001]-oriented ZnO nanowire cantilever at elevated temperatures were measured using scanning laser Doppler vibrometry. The temperature-dependent Young's moduli were derived from the resonant frequencies using Euler-Bernoulli beam theory. It was found that the modulus of ZnO nanowires decreased linearly with the increase of temperature from 300 to 650 K, independent of the nanowire diameter ranged from 101 to 350 nm. The temperature coefficient that defines the linear relationship between the dimensionless modulus and temperature is [Formula: see text] which agrees with that of [Formula: see text] being calculated using molecular dynamics with a partially charged rigid ion model.

Application of nanotechnology in biosensors for enhancing pathogen detection

Rapid detection and identification of pathogenic microorganisms is fundamental to minimizing the spread of infectious disease, and informing clinicians on patient treatment strategies. This need has led to the development of enhanced biosensors that utilize state of the art nanomaterials and nanotechnology, and represent the next generation of diagnostics. A primer on nanoscale biorecognition elements such as, nucleic acids, antibodies, and their synthetic analogs (molecular imprinted polymers), will be presented first. Next the application of various nanotechnologies for biosensor transduction will be discussed, along with the inherent nanoscale phenomenon that leads to their improved performance and capabilities in biosensor systems. A future outlook on characterization and quality assurance, nanotoxicity, and nanomaterial integration into lab-on-a-chip systems will provide the closing thoughts. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > Biosensing.

Actuation of higher harmonics in large arrays of micromechanical cantilevers for expanded resonant peak separation

A large array of elastically coupled micro cantilevers of variable length is studied experimentally and numerically. Full-scale finite element modal analysis is implemented to determine the spectral behavior of the array and to extract a global coupling matrix. A compact reduced order model is used for numerical investigation of the array's dynamic response. Our model results show that at a given excitation frequency within a propagation band, only a finite number of beams respond. Spectral characteristics of individual cantilevers, inertially excited by an external piezoelectric actuator, were measured in vacuum using laser interferometry. The theoretical and experimental results collectively show that the resonant peaks corresponding to individual beams are clearly separated when operating in vacuum at the 3^rd harmonic. Distinct resonant peak separation, coupled with the spatially-confined modal response, make higher harmonic operation of tailored, variable-length cantilever arrays well suited for a variety of resonant based sensing applications.

Young's modulus and indirect morphological analysis of Bi2Se3 nanoribbons by resonance measurements

An electrostatically induced resonance behaviour of individual topological insulator Bi₂Se₃ nanoribbons grown by a catalyst free vapour-solid synthesis was studied in situ by scanning electron microscopy. It was demonstrated that the relation between the resonant frequencies of vibrations in orthogonal planes can be applied to distinguish the nanoribbons with rectangular cross-sections from the nanoribbons having step-like morphology (terraces). The average Young's modulus of the Bi₂Se₃ nanoribbons with rectangular cross-sections was found to be 44 ± 4 GPa.

The Mechanical Properties of Nanowires

Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed.

Vapor-phase synthesis, growth mechanism and thickness-independent elastic modulus of single-crystal tungsten nanobelts

Single-crystal tungsten nanobelts with thicknesses from tens to hundreds of nanometers, widths of several micrometers and lengths of tens of micrometers were synthesized using chemical vapor deposition. Surface energy minimization was believed to have played a crucial role in the growth of the synthesized nanobelts enclosed by the low-energy {110} crystal planes of body-centered-cubic structure. The anisotropic growth of the crystallographically equivalent {110} crystal planes could be attributable to the asymmetric concentration distribution of the tungsten atom vapor around the nanobelts during the growth process. The elastic moduli of the synthesized tungsten nanobelts with thicknesses ranging from 65 to 306 nm were accurately measured using a newly developed thermal vibration method. The measured modulus values of the tungsten nanobelts were thickness-dependent. After eliminating the effect of surface oxidization using a core-shell model, the elastic modulus of tungsten nanobelts became constant, which is close to that of the bulk tungsten value of 410 GPa.

Lead zirconate titanate nanoscale patterning by ultraviolet-based lithography lift-off technique for nano-electromechanical system applications

The advantage of using lead zirconate titanate (PbZr(0.54)Ti(0.46)O(3)) ceramics as an active material in nanoelectromechanical systems (NEMS) comes from its relatively high piezoelectric coefficients. However, its integration within a technological process is limited by the difficulty of structuring this material with submicrometer resolution at the wafer scale. In this work, we develop a specific patterning method based on optical lithography coupled with a dual-layer resist process. The main objective is to obtain sub-micrometer features by lifting off a 100-nm-thick PZT layer while preserving the material's piezoelectric properties. A subsequent result of the developed method is the ability to stack several layers with a lateral resolution of few tens of nanometers, which is mandatory for the fabrication of NEMS with integrated actuation and read-out capabilities.