研究目的
To present a novel method for monitoring liquid condition by tracking density using Piezoelectric Micromachined Ultrasound Transducers (PMUTs) in a PMUT-Fluid-PMUT arrangement.
研究成果
The PFP system using PMUTs is feasible for fluid density sensing with high sensitivity (up to 365 Hz/kg/m3) and low error (<1%). It shows promise for applications in process industries and microfluidic devices due to small size, customizability, and fast response. Future work should address theoretical discrepancies and turbulent flow effects.
研究不足
The theoretical assumptions, such as wavelength being smaller than plate size, are not fully satisfied at the microscale studied. Effects of turbulent flow on sensitivity are not thoroughly investigated and may cause fluctuations. The resolution and range depend on frequency sweep bandwidth and PMUT design.
1：Experimental Design and Method Selection:
The study uses a PMUT-Fluid-PMUT (P-F-P) arrangement for density sensing based on the virtual added mass effect, where the natural frequency shift of PMUTs in fluid is measured. Theoretical models from Lamb and Kwak are employed.
2：Sample Selection and Data Sources:
Glycerol-water mixtures with varying concentrations are prepared, and their densities are measured by weighing mass for a fixed volume.
3：List of Experimental Equipment and Materials:
PMUT arrays (fabricated with silicon and PZT layers, diameters of 1000μm, 500μm, 250μm), lock-in amplifier (Zurich Instruments MFLI), D.C supply, peristaltic pump (discharge rate 90 mL/min), laser Doppler vibrometer (Polytec MSA 500), and glycerol-water mixtures.
4：Experimental Procedures and Operational Workflow:
PMUT arrays are aligned facing each other with fluid in between, maintaining a distance of at least 10 times the radius. The top PMUT acts as transmitter, bottom as receiver. Frequency sweeps are performed using the laser Doppler vibrometer for PMUT characterization and lock-in amplifier for PFP arrangement. Mixtures are circulated using the peristaltic pump for dynamic conditions.
5：Data Analysis Methods:
Sensitivity is calculated as the rate of change of frequency with respect to density. Theoretical and experimental sensitivities are compared, and errors are computed as percentage differences.
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