Detecting both the mass and position of an accreted particle by a micro/nano-mechanical resonator sensor

Vibration Control of Diamond Nanothreads by Lattice Defect Introduction for Application in Nanomechanical Sensors

Carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene sheets (GSs), have been adopted as resonators in vibration-based nanomechanical sensors because of their extremely high stiffness and small size. Diamond nanothreads (DNTs) are a new class of one-dimensional carbon nanomaterials with extraordinary physical and chemical properties. Their structures are similar to that of diamond in that they possess sp3-bonds formed by a covalent interaction between multiple benzene molecules. In this study, we focus on investigating the mechanical properties and vibration behaviors of DNTs with and without lattice defects and examine the influence of density and configuration of lattice defects on the two them in detail, using the molecular dynamics method and a continuum mechanics approach. We find that Young’s modulus and the natural frequency can be controlled by alternating the density of the lattice defects. Furthermore, we investigate and explore the use of DNTs as resonators in nanosensors. It is shown that applying an additional extremely small mass or strain to all types of DNTs significantly changes their resonance frequencies. The results show that, similar to CNTs and GSs, DNTs have potential application as resonators in nano-mass and nano-strain sensors. In particular, the vibration behaviors of DNT resonators can be controlled by alternating the density of the lattice defects to achieve the best sensitivities.

Mode Localization and Eigenfrequency Curve Veerings of Two Overhanged Beams

Overhang provides a simple but effective way of coupling (sub)structures, which has been widely adopted in the applications of optomechanics, electromechanics, mass sensing resonators, etc. Despite its simplicity, an overhanging structure demonstrates rich and complex dynamics such as mode splitting, localization and eigenfrequency veering. When an eigenfrequency veering occurs, two eigenfrequencies are very close to each other, and the error associated with the numerical discretization procedure can lead to wrong and unphysical computational results. A method of computing the eigenfrequency of two overhanging beams, which involves no numerical discretization procedure, is analytically derived. Based on the method, the mode localization and eigenfrequency veering of the overhanging beams are systematically studied and their variation patterns are summarized. The effects of the overhang geometry and beam mechanical properties on the eigenfrequency veering are also identified.

Critical conditions for escape of a high-speed fullerene from a BNC nanobeam after collision

For a resonator-based nano-balance, the capability of capturing a nanoparticle is essential for it to measure the mass of the particle. In the present study, a clamped-clamped nanobeam from a Boron-Nitride and Carbon (BNC) nanotube acts as the nano-balance, and a fullerene, e.g., C60, is chosen as the particle, and the capturing capability is quantitatively estimated by the minimal escape velocity (MEV) of the fullerene from the nanobeam after collision. When centrally colliding with the nanobeam, the escape of fullerene depends on both incidence of fullerene and temperature of the system. When the colliding in the Boron-Nitride (BN) area of the beam surface, the nanoball escapes easier than that at the carbon area. The MEV of the nanoball is lower at higher temperature. As the nanoball sometimes slides for a few pica-seconds on the beam surface before being bounced out, the nanoball can escape only when the beam surface can provide the nanoball enough kinetic energy to overcome the van der Waals interaction between them. The capturing capability of the nano-balance can, thus, be improved by reducing the initial kinetic energy of the system.

Mass and Force Sensing of an Adsorbate on a Beam Resonator Sensor

The mass sensing superiority of a micro-/nano-mechanical resonator sensor over conventional mass spectrometry has been, or at least is being firmly established. Because the sensing mechanism of a mechanical resonator sensor is the shifts of resonant frequencies, how to link the shifts of resonant frequencies with the material properties of an analyte formulates an inverse problem. Besides the analyte/adsorbate mass, many other factors, such as position and axial force, can also cause the shifts of resonant frequencies. The in situ measurement of the adsorbate position and axial force is extremely difficult if not impossible, especially when an adsorbate is as small as a molecule or an atom. Extra instruments are also required. In this study, an inverse problem of using three resonant frequencies to determine the mass, position and axial force is formulated and solved. The accuracy of the inverse problem solving method is demonstrated, and how the method can be used in the real application of a nanomechanical resonator is also discussed. Solving the inverse problem is helpful to the development and application of a mechanical resonator sensor for two reasons: reducing extra experimental equipment and achieving better mass sensing by considering more factors.