A droplet-based micropillar-enhanced acoustic wave (?PAW) device for viscosity measurement

Viscosity monitoring has recently received significant attention in various fields such as pharmacy, oil industry, food industry, and medical diagnostics. Given that the commercially available viscometers usually require a large sample volume to conduct accurate measurement, there is an urgent need to develop a viscometer that can consume the least sample while maintaining high accuracy. Despite of being simple, rapid, and cost-effective, quartz crystal microbalance (QCM) based viscometers are low in sensitivity and not able to measure viscosity directly. This work focuses on the development of a novel micropillar-enhanced QCM viscosity measurement device which relies on the coupled vibration between micropillars and quartz substrate (QCM-P) to achieve an ultra-sensitive viscosity measurement of a sample droplet. A hybrid model by integrating an equivalent circuit and numerical simulation approach was established to understand the working principle of the QCM-P device and evaluate the viscosity value. The experimental results and analysis demonstrate that the micropillar-enhanced acoustic wave (mu PAW) devices such as QCM-P viscometer is a promising device for droplet-based viscosity measurement.