MagSity platform: a hybrid magnetic levitation-based lensless holographic microscope platform for liquid density and viscosity measurements

Abstract

The viscosity and density of liquids are the most extensively studied material properties, as their accurate measurement is critical in various industries. Although developments in micro-viscometers have overcome the limitations of traditional bulky methods, more accessible technologies are required. Here, we introduce a novel magnetic levitation-based method to measure the viscosity and density of solutions in a microcapillary channel. This principle exploits microparticles as microsensors to correlate levitation time and height with solutions' viscosity and density, using buoyancy and drag forces. The platform has an integrated lensless holographic microscope, providing a hybrid system for in situ and precise measurements. By utilizing this hybrid technology, portable, rapid and cost-effective measurements can be conducted. This platform enables viscosity and density measurements within 7 minutes, achieving high accuracies of at least 97.7% and 99.9%, respectively, across an operation range of 0.84–5.09 cP and 1.00–1.09 g cm⁻³. The platform is utilized to clearly distinguish differences in the spent cell culture medium across various cell lines. This method, as presented, can be readily applied to measure a diverse array of liquids in multiple domains, encompassing biotechnology, medicine, and engineering.