μ-'Diving suit' for liquid-phase high-Q resonant detection.

Area of Science:

• * Micro/Nano-electromechanical Systems (MEMS)
• * Chemical and Biological Sensing
• * Materials Science and Engineering

Background:

• * Resonant micro-cantilever sensors offer high sensitivity for trace-level detection.
• * Operation in liquid environments is challenging due to liquid damping and non-specific adsorption.
• * Existing methods struggle with long-term stability and accurate real-time measurements in solution.

Purpose of the Study:

• * To develop a waterproof coating for resonant micro-cantilevers to enable stable liquid-phase operation.
• * To overcome limitations of liquid damping and non-specific adsorption for enhanced sensor performance.
• * To achieve long-time, high-Q resonance for real-time bio/chemical detection in aqueous solutions.

Main Methods:

• * Fabrication of a micro-cantilever with a patterned photoresist sacrificial layer and a hydrophobic parylene waterproof coat.
• * Formation of an air gap between the coat and cantilever to mitigate liquid damping.
• * Design of a localized sensing pool at the cantilever tip and a hydrophobic slit for anti-leakage, integrated with electro-thermal excitation and piezoresistive readout.

Main Results:

• * Achieved a Q-factor of 23 in water and continuous operation exceeding 20 hours.
• * Demonstrated real-time detection of ppb-level acephate pesticide and E. coli DH5α using specific sensing materials.
• * Successfully addressed the long-standing challenge of operating resonant micro-sensors effectively in liquid.

Conclusions:

• * The developed 'diving suit' technology fundamentally enables robust and long-term operation of resonant micro-cantilever sensors in liquid.
• * This innovation opens new avenues for sensitive, real-time bio/chemical analysis in diverse aqueous environments.
• * The lab-chip micro-system provides a powerful platform for liquid-phase detection with high sensitivity and stability.