IJE TRANSACTIONS B: Applications Vol. 33, No. 2, (February 2020) 320-328 Please cite this article as: M. Soosani, M. Fathalilou, G. Rezazadeh, M. Homaei, Generating and Focusing the Ultrasound Waves Using Elastomer- Based Capacitive Micro-Speakers, International Journal of Engineering (IJE), IJE TRANSACTIONS B: Applications Vol. 33, No. 2, (February 2020) 320-328 International Journal of Engineering Journal Homepage: www.ije.ir Generating and Focusing the Ultrasound Waves Using Elastomer-based Capacitive Micro-Speakers M. Soosani a , M. Fathalilou* a , G. Rezazadeh a,b , M. Homaei a a Mechanical Engineering Department, Urmia University, Urmia, Iran b Institute of Engineering and Technology, South Ural State University, Chelyabinsk, Russian Federation PAPER INFO Paper history: Received 21 Octeber 2019 Received in revised form 03 November 2019 Accepted 08 November 2019 Keywords: Ultrasound Micro-speaker MEMS Dielectric Elastomers Bessel Panel Focused Pressure Pattern ABSTRACT 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. doi: 10.5829/ije.2020.33.02b.17 NOMENCLATURE 1 J First order Bessel function  Maxwell stress [ ] M Mass matrix 0  Initial pre-stress [] B Damping matrix  Relative dielectric permittivity of the elastomer [ ] K Stiffness matrix 0  Vacuum permittivity p P Acoustic pressure D Bending rigidity of the micro-plate 0  Air density  Poisson’s ratio 0 c Sound velocity in air 4  Biharmonic operator k Wavenumber 2  Laplace operator 0 U Amplitude of the piston’s velocity str T Stretching  excitation frequency 1. INTRODUCTION 1 There are three types of acoustic waves according to their frequency: A) waves of less than 20Hz is called "subsonic", B) human audible sounds have a frequency of about 20 to 20,000Hz, and C) "Ultrasound" is a sound wave whose frequency exceeds 20,000Hz. In 1876, *Corresponding Author Email: m.fathalilou@urmia.ac.ir (M. Fathalilou) Francis Galton first discovered the existence of ultrasound. The initial investigation of ultrasound has been in biologic systems and its biologic effects [1]. Ultrasound is becoming a key and useful instrument in diagnostic and therapeutic tools in current clinical practice. Research on the using of the ultrasound and its medical applications are of great importance today, due