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Ultrasound wave is a kind of waves with the frequency higher than the human audible frequency. Although ultrasound was first used for military identification purposes, it has been used for decades for various other applications, especially medical applications. Medical applications of ultrasound include diagnostic and therapeutic applications, such as for the treatment of cancer. In this paper, for the first time, electrostatically-actuated micro-speakers made of a dielectric elastomer (DE) have been used to generate and focus the ultrasonic waves using Micro-Electro-Mechanical Systems (MEMS) technology. The results have shown that a single micro-speaker could not generate an efficient focused wave, so an array of the micro-speakers has been considered. The layout of the micro-speakers is a square array of Bessel Panel. It has been shown that by adopting a suitable excitation frequency as well as number of the elements in the Bessel’s panel, the DE-based capacitive micro-structures can focus the generated sound wave in a pre-determined area.

The purpose of this research is to study the mechanical behavior of a micropump with clamped circular diaphragm which is the main component of drug delivery systems. In this paper, the non-linear governing equations of the circular microplate using Kirchhoff thin plate theory was been extracted based on the modified couple stress (MCST) and classical (CT) theories. Then, the non-linear equation of static deflection is solved using Step-by-Step Linearization Method (SSLM) in order to escape the nonlinearity of the differential equation and Galerkin-based reduced-order model is applied to investigate the dynamic motion of the microplate. Afterwards, static and dynamic stabilities of the micropump have been studied based on both MCST and CT, then compared. Also, volumetric flow rate of the micropump was been delved based on both theories and in entire research, presence of the length scale parameter in modified couple stress theory brings this opportunity to study the size effect on the mechanical behavior of the micropump.

A B S T R A C T This article deals with the mechanical analysis of a fixed-fixed nano-beam based on nonlocal theory of elasticity. The nano-beam is sandwiched with two piezoelectric layers through its upper and lower surfaces. The electromechanical coupled equations governing the problem are derived based on nonlocal theory of elasticity considering Euler-Berno ulli beam assumptions. Also, nonlocal piezoelectricity is according to Maxwell’s electrostatic equations. The piezoelectric layers are subjected to a voltage to tune the stiffness of the nano-beam. The equations are solved through step by step linearization method and Galerkin’s weighted residual method. The results are compared with those of the local model. The effect of piezoelectric voltages on the non-locality of the model is investigated as well .

In this article thermoelastic damping in nano-beam resonators is investigated based on nonlocal theory of elasticity and the Euler-Bernoulli beam assumptions. The governing equation of deflection of the beam is obtained from shear and moment resultants and stress–strain relationship of the nonlocal elasticity model and also the governing equations of thermoelastic damping are established by using, two dimensional non-Fourier heat conduction with one relaxation time based on continuum theory frame. Free vibration of the nano-beam resonators is analyzed using Galerkin reduced order model formulation for the first mode of vibration. In the present investigation a clamped-clamped nano-beam with isothermal boundary conditions at both ends is studied. This nonlocal nano-beam model incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect. The obtained results are compared with the numerical results of the classical thermoelastic models. Thermoelastic damping effects on the damping ratio are studied for the various nano-beam thicknesses and ambient temperatures. In addition to, the study includes computations for different values of nonlocal theory parameter. The results show that with increasing the amount of nonlocal parameter and also with decreasing the length of the nano-beam, difference of the results of classical and nonlocal theory increases.