Rational design of wettability-patterned microchips for high-performance attomolar surface-enhanced Raman detection

Area of Science:

• Materials Science and Engineering
• Analytical Chemistry
• Nanotechnology

Background:

• Wettability-patterned microchips enable ultra-trace detection in biomedical and food safety applications.
• Analyte deposition in superhydrophilic traps is crucial for sensitivity.
• Wetting transitions during evaporation enlarge deposition footprints, reducing detection sensitivity and uniformity.

Purpose of the Study:

• To develop an integrated design, fabrication, and evaporation strategy to prevent wetting transitions in microchips.
• To achieve high-performance attomolar detection using surface-enhanced Raman scattering (SERS).
• To improve detection sensitivity and uniformity for ultra-trace molecules in aqueous solutions.

Main Methods:

• Designed microstructures using an improved force balance model.
• Fabricated wettability-patterned microchips via nanosecond laser direct writing and surface fluorination.
• Employed a two-step heated evaporation strategy to control analyte deposition.

Main Results:

• Achieved targeted deposition of analytes onto a minimal area (∼70 × 70 μm²).
• Reached an ultra-low detection limit at the attomolar level (5 × 10⁻¹⁸ M) with SERS enhancement factors > 10¹⁰.
• Demonstrated good signal uniformity (RSD of 11.5%) and a wide linear quantitative range (10⁻¹² M to 5 × 10⁻¹⁸ M).

Conclusions:

• The proposed strategy effectively avoids wetting transitions, enabling high-performance attomolar SERS detection.
• Wettability-patterned microchips offer high sensitivity and uniformity for ultra-trace molecule detection without specialized equipment.
• The strategy is applicable to other microfluidic devices for simple and rapid analyte pre-concentration.