This paper investigates the postbuckling and free vibration response of geometrically imperfect multilayer nanobeams. The beam is assumed to be subjected to a pre-stress compressive load due to the manufacturing and its ends are kept at a fixed distance in space. The small-size effect is modeled according to the nonlocal elasticity differential model of Eringen within the nonlinear Bernoulli-Euler beam theory. The constitutive equations relating the stress resultants to the cross-section stiffness constants for a nonlocal multilayer beam are developed. The governing nonlinear equation of motion is derived and then manipulated to be given in terms of only the lateral displacement. The static problem is solved for the buckling load and the postbuckling deflection in terms of three parameters: Imperfection amplitude, size, and lamination. A closed-form solution for the buckling load in terms of all of the beam parameters is developed. With the presence of imperfection and size effects, it has been shown that the buckling load can be either less or greater than the Euler buckling load. Moreover, the free vibration in the pre and postbuckling domains are investigated for the first five modes. Numerical results show that the effects of imperfection, the nonlocal parameter, and layup on buckling loads and natural frequencies of the nanobeams are significant.

We experimentally investigate the primary superharmonic of order two and subharmonic of order one-half resonances of an electrostatic MEMS actuator under direct excitation. We identify the parameters of a one degree of freedom (1-DOF) generalized Duffing oscillator model representing it. The experiments were conducted in soft vacuum to reduce squeeze-film damping, and the actuator response was measured optically using a laser vibrometer. The predictions of the identified model were found to be in close agreement with the experimental results. We also identified the noise spectral density of process (actuation voltage) and measurement noise.

Research into sustainable energy sources has gained significant attention due to global environmental challenges. Vibration energy harvesting (VEH) presents a promising approach for developing self-powered sensors, offering both practical and environmental benefits. This paper reviews recent advancements in VEH with a specific focus on piezoelectric-based methods. It classifies the key techniques in the literature into categories such as multistability (including bistability), internal resonance, optimized designs, and frequency-up conversion. The paper discusses the underlying principles of each technique, provides relevant illustrations, highlights recent studies within each category, and summarizes their main contributions.

This work presents a comprehensive model for nanobeams, incorporating beam curvature and surface energy. Gurtin–Murdoch surface stress theory is used, in conjunction with Euler–Bernoulli beam theory, to model the beams and take surface energy effects into consideration. The model was validated by contrasting its outcomes with experimental data published in the literature on the static bending of fixed–fixed and fixed–free nanobeams. The outcomes demonstrated that surface stress alters the stiffness of both fixed–fixed and fixed–free nanobeams with different behaviors in each case.

This paper investigates the performance of cantilever-type micro-mirrors under electromagnetic, electrostatic and dual actuation. We developed and validated a two-DOFs model of the coupled bending-torsion motions of the mirror and used it in conjunction with experiments in air and in vacuum to compare all three actuation methods. We found that electromagnetic actuation is the most effective delivering a scanning range of ± out of a geometrically allowable range of ± at a current amplitude i = 3 mA and a magnetic field of B = 30 mT. Electrostatic actuation, whether alone or in conjunction with electromagnetic actuation, limited the stable angular range to smaller values (as small as ) due to the presence of spurious piston motions. This is an innate characteristic of micro-scale electrostatic actuation, the electrostatic force and the undesirable piston motion grow faster than the electrostatic torque and the desired angular displacement as the voltage is increased and they limit the stable angular range. Finally, we found that the dual actuation can be used to design two-DOF mirrors where electromagnetic actuation drives angular motion for optical beam steering and electrostatic actuation drives piston motion to control the mirror focus.