(Invited) Fluid Spectroscopy with Piezoelectric Ultrasound MEMS Transducers

• Published in: ECS transactions 2018-01, Vol.86 (16), p.13-20
• Main Authors: Pratap, Rudra, Dangi, Ajay, Roy, Kaustav, Gupta, Harshvardhan
• Format: Article
• Language: English
• ISSN: 1938-5862; 1938-6737; 1938-6737; 1938-5862
• DOI: 10.1149/08616.0013ecst

In this work, Piezoelectric Micromachined Ultrasound Transducers (PMUTs) are explored as a potential MEMS solution for fluid property monitoring. PZT based PMUTs fabricated with three different diameters-1000 μm, 500 μm, 250 μm-showing in-air resonant frequencies between 100 kHz to 2 MHz are tested in water-glycerol mixtures with glycerol concentrations varying between 0% to 80% in both static and dynamic conditions. Spectral shifts of PMUT vibrations with changing fluid environment are quantitatively related to the density and viscosity of the fluid. The density sensitivity of the PMUTs is found to increase from 27 Hz/kg.m-3 for 1000 μm to 365 Hz/kg.m-3 for 250 µm, which is in close agreement with theoretical expectations. Similarly, viscosity sensing is also explored using PMUT arrays. A through-the-fluid ultrasound transmission architecture is proposed for a potential fluid property sensor that can fill the gap of miniature sensors for sensing physical properties of various fluids.