Design and implementation of a passive micro flow sensor based on diamagnetic levitation

This study presents a prototype of a micro-flow sensor based on magnetic levitation for the use in microfluidic systems. Accurate assessment of flow rates is crucial in the microfluidic system design. Micro-sensors utilizing levitation constitute an important topic in this regard. Diamagnetic levitation is an efficient technique, which is useful in applications with low power consumption and eliminates friction. With the proposed approach, zero mechanical contact in a microfluidic channel can be achieved. A sensor capable of accurately measuring flow rates was designed in this study. The corresponding flow rate range was between 1000 μL/min and 7000 μL/min. Levitation was accomplished with pyrolytic graphite and a ring magnet (NdFeB) acting as a lifter. The displacement of the micro-magnet in the micro channel in longitudinal direction was monitored via a microscope-camera system and was measured via a laser sensor above the lifter-magnet. A commercial analysis software (COMSOL Multiphysics Version 5.3 CPU License No: 17076072) was used for dynamic analysis and validation of experimental results. The flow rates were obtained using the data from the laser sensor via an exclusively coded C# program. The developed sensor prototype, which has the advantages of simple structure, small size and low cost, is a substantial candidate for the use in microfluidic devices requiring high accuracy