1 3 J Braz. Soc. Mech. Sci. Eng. (2017) 39:4955–4963 https://doi.org/10.1007/s40430-017-0788-7 TECHNICAL PAPER Study of micropolar fluid flow inside a magnetohydrodynamic micropump E. Alizadeh-Haghighi 1 · S. Jafarmadar 1 · Sh. Khalil Arya 1 · G. Rezazadeh 1 Received: 27 February 2015 / Accepted: 5 March 2017 / Published online: 24 May 2017 © The Brazilian Society of Mechanical Sciences and Engineering 2017 1 Introduction Application of Microelectromechanical systems (MEMS) and nanoelectromechanical systems is becoming consid- erably prevalent for variety of scientific and engineering applications [1, 2]. With the recent development of MEMS technologies, variety of studies has been performed in microfluidic systems. For instance, microvalves, micro- pumps, and flow sensors are interdisciplinary systems combining fluid mechanics and micromachining technolo- gies [3–5]. Due to their ability to control and regulate pre- cise and small volumes of fluids, micropumps are the most commonly employed components in biological, chemical, and medical applications such as microsyringes for dia- betics. However, in many situations some of fluid proper- ties which restrict certain principle to a small class of flu- ids, impact their performance considerably. Micropumps are mainly classified into two categories: mechanical and non-mechanical (without moving parts) micropumps [4]. Mechanical micropumps are actuated considering variety of actuating principles, such as, electrostatic, thermopneu- matic, piezoelectric, and magnetic ones [6, 7]. Wear and fatigue of the input–output check valves and high-pressure drop across them, are common problems in those micro- pumps [8]. Hence, micropumps without movable parts such as electrohydrodynamic (EHD), magnetohydrodynamic (MHD) and valveless diffuser–nozzle micropumps were presented. A diffuser–nozzle valveless micropump was pre- sented by Stemme and Stemme [8].The working principle of the micropump is that net volume from the inlet side to the outlet side is pumped since generally, for a given pres- sure drop, the volume flow is higher in diffuser than in noz- zle direction. Comparatively high pump volume and simplicity are features of these kinds of pumps. The other type of Abstract In this paper, a magnetohydrodynamic micro- pump with side-walled electrodes has been studied. Micro- pump was fabricated using MEMS technology and applied Lorentz force induced as a result of interaction between an applied electric field and a perpendicular magnetic field to pump the continuous steady, incompressible and fully developed laminar conducting fluid. Since the micro-pump dimensions are comparable to that of the fluid molecules, the assumption of the continuum fluid theory is no longer justified. Hence, micropolar fluid theory is considered in this study. Application of the theory of fluid dynamics and electromagnetic led to derivation of governing equations of the corresponding momentum and angular momentum. The governing equations and their associated boundary condi- tions were first cast into dimensionless form. The resulting partial differential equations were solved numerically using finite difference technique and the profiles of the velocity and microrotations are obtained. The results for a special case were compared with the experimental ones and they showed a good agreement with each other. Furthermore, the effects of coupling number, Hartmann number and micropolar parameter on the velocity, microrotation and flow rate are discussed. Keywords MEMS · Magnetohydrodynamics · Micropump · Micropolar fluid · Lorentz force Technical Editor: Marcio S Carvalho. * G. Rezazadeh g.rezazadeh@urmia.ac.ir 1 Mechanical Engineering Department, Urmia University, Urmia, Iran