Experimental and theoretical investigation on magnetic fluid seal in capillary tube

Abstract The application of magnetic fluid (MF) in microfluidics such as micropump and microvalve has been a hot topic recent years. Furthermore, the researches and the applications of MF seal are relatively mature and systematic. However, the seal capacity, which significantly influences the performance of micropump and microvalve, has not been studied specifically and overly. This paper focuses on the theoretical and experimental study about the seal capacity of MF seal in capillary tube. Furthermore, the influence of the clearance between the heads of steel poles, the inner diameter of the capillary tube, and the length of MF plug is investigated numerically and experimentally. In the simulation work, the conventional calculation model of magnetic pressure is applied to the occasion under the presence of low magnetic field and the simulation of magnetic field in the capillary tube is also conducted. Subsequently, the experiments are conducted and compared with our theoretical simulation results. In order to improve the prediction of the theory, the influence of viscosity is considered and the optimized theoretical results are compared with conventional theoretical results, which revealed that the viscosity cannot be ignored in the study of MF seal in capillary tube.