Smart Materials in Action: Application of Magnetorheological Fluids in Micropump Design

Abstract

Smart materials that can change their properties in response to external stimuli offer exciting possibilities for innovative device design. One such material is magnetorheological (MR) fluid, which undergoes a reversible change in rheological properties in the presence of a magnetic field. This enables active control of fluid flow properties. In this work, we report the design, fabrication and testing of an MR fluid-based micropump capable of variable flow rate control. The micropump utilizes soft lithography techniques to pattern microfluidic channels onto a polydimethylsiloxane substrate bonded to glass. Miniature electromagnetic coils surrounding the microchannel actively control the viscosity of MR fluid within the pump chamber. Applying current to the coils creates a magnetic field which triggers formation of micron-sized particle chains in the MR fluid. This rapidly increases fluid viscosity and enables precise adjustment of flow resistance and pumping rate. We demonstrate continuous flow rate control over a wide range spanning 0 - 1.5 ml/min with response times under 50 ms upon applying field pulses. The pump is also capable of on/off switching functionality. Our prototype represents a simple, fast-response active microfluidic system with potential lab on chip analytical applications. Further miniaturization and optimization of control electronics could enable practical biomedical applications such as programmable drug delivery systems. The integration of smart fluids with microfluidics thus offers a versatile platform for creating rapidly actuated, precisely controlled microscale pumps and valves.