Hand-held, automatic capillary viscometer for analysis of Newtonian and non-Newtonian fluids

Abstract

Despite advances in measuring fluid viscosity, we still lack portable viscometers to analyze shear rate-varying fluid characteristics in the form of open-source hardware that non-expert users can easily make and use. We present a hand-held, automatic capillary viscometer, termed "Viscopette", which can be fabricated simply by assembling globally available mechanical (a stepper motor and an inline pressure sensor), fluidic (a positive-displacement pipette and a cut tubing piece), electronic (an Arduino board) parts in a 3D-printed housing. The Viscopette is specifically designed to improve user experience by adopting how to use commercial micropipettes, and fits within 7.3 cm × 7.3 cm × 38.8 cm (without the cut tubing piece) with an overall weight of 437 g for portable use. By exploiting the high level of controllability of the open-source microcontroller, the Viscopettes enables time-varying shear-rate (or flow-rate) control for viscosity analysis, and simple viscosity measurement by calculating the ratio of a pressure value measured using the inline pressure sensor and a set flow-rate condition. With the advantages of ease-of-use, portability, and shear-rate controllability, we demonstrate the Viscopette's ability to accurately analyze Newtonian and non-Newtonian fluids. Our method addresses the unmet need in portable, high-performance viscometers suitable for use as an open-source equipment, which can facilitate on-site, accurate viscosity analysis even by non-expert users.