A Microfluidic MEMS-Microbalance Platform With Minimized Acoustic Radiation in Liquid

Area of Science:

• Micro/nanotechnology
• Sensor technology
• Materials science

Background:

• Microscale resonant sensors require robust liquid interfacing.
• Acoustic energy loss and signal interference are challenges in liquid environments.
• Thin-film piezoelectric-on-silicon (TPoS) sensors offer high sensitivity but need effective liquid handling.

Purpose of the Study:

• To integrate microfluidic channels into the backside of TPoS resonators.
• To investigate the effect of a parylene isolation layer on sensor performance in liquid.
• To characterize Lamb wave modes and optimize TPoS sensors for liquid-based mass sensing.

Main Methods:

• Fabrication of TPoS resonators with backside-integrated microwells on silicon-on-insulator (SOI) wafers.
• Application of a parylene isolation layer of varying thicknesses.
• Characterization of resonator performance in air and liquid using PDMS-based microfluidic channels.
• Experimental validation of acoustic energy radiation effects.

Main Results:

• The parylene layer significantly enhances TPoS sensor performance in liquid media.
• High quality factors (Q > 400) were achieved for specific symmetric (S) Lamb wave modes, such as S(4, 2).
• Acoustic energy radiation into liquid was experimentally validated, impacting Q and resonance frequency.

Conclusions:

• Backside microfluidic integration with a parylene isolation layer effectively mitigates acoustic energy loss in TPoS sensors.
• The developed TPoS sensor architecture demonstrates potential for highly stable and sensitive microbalance applications.
• This approach facilitates real-time mass sensing with improved performance in liquid environments.