Performances of microvalve using magnetorheological fluid droplet as switching element

Abstract Magnetorheological fluid (MRF) can be made to behave like a solid in a magnetic field, controlling microchannel flow. A novel microchannel valve design employs a MRF droplet and magnetic field for valve control. The proposed valve assembly incorporates a permanent magnet array, a MRF droplet and a microchannel integrated by a reservoir. By regulating the permanent magnet array, the MRF droplet may stay in the reservoir or fill in the microchannel, thus resulting in the open and close of the channel, respectively. The numerical simulation as well as experimental validation was conducted to investigate the effects of geometrical parameters of reservoir on the morphology and pressure resistance of the MRF droplet. A reservoir length of 6 mm yields a response time of approximately 2.1 s for valve closure and 0.5 s for valve opening, respectively. At a flow rate of 5 µl/min, a combined experimental and simulation approach has been employed to predict potential leakage points of magnetorheological fluid droplet valves with different reservoir lengths. It can be seen that when the reservoir length between 6 and 14 mm, the rupture point of the MRF droplet occurs near the junction between the reservoir and the channel. Nevertheless, for the length between 16 and 18 mm, the rupture subsequently relocated to the upper portion of the channel. A comprehensive analysis of the influence of reservoir length on the pressure resistance of the valve shows a changing pattern, indicating that the valve exhibits optimal pressure resistance at the length of 12 mm, with the critical pressure difference around 600 Pa.