A comprehensive review on MEMS-based viscometers

Viscosity is an important rheological parameter, which needs to be measured accurately in various industrial applications to improve the quality of the product. Micro-electro-mechanical system (MEMS)-based microfluidic viscometers are nowadays overpowering conventional types of viscometers due to many advantages such as compatibility for both Newtonian and non-Newtonian fluids, small size, higher shear rates, no solvent evaporation, small sample size requirement (in micro and nano-litres), and better accuracy. This paper summarizes a comprehensive review on the state-of-the-art of MEMS-based technologies combined with microfluidics for realizing the viscometers to determine various fluidic parameters, important for applications in different fields like biopharmaceuticals and protein therapeutics, lubricants/adhesives, healthcare, food industries, cosmetics, concrete, paints, fuel and petroleum industries, etc. This review covers the basic sensing principles of various types of MEMS-based technologies useful for viscometer applications, such as pressure, diaphragm, viscometer/rheometer on a chip (VROC), acoustic, cantilever etc. Limitations of different types of commonly available tabletop viscometers are outlined. Considering the present and future applications of MEMS-based viscometers, their role in industrial applications are also discussed in detail.