Visual Detection Strategy Based on Size-Gradient Coffee Rings on a Superslippery Platform.

Area of Science:

• Analytical Chemistry
• Materials Science
• Surface Science

Background:

• Superslippery surfaces are known for resisting the coffee-ring effect due to their unique properties.
• Traditional analytical methods often require complex instrumentation and sample preparation.

Purpose of the Study:

• To develop a novel strategy for dynamic coffee-ring formation on superslippery surfaces for analyte detection.
• To enable both qualitative and quantitative visual detection of target analytes.

Main Methods:

• Functionalizing superslippery surfaces to induce affinity recognition with target analytes.
• Leveraging synergistic interactions between the coffee-ring effect and mobile contact line properties.
• Utilizing suspended micro-/nanoparticles for visualization of coffee rings.

Main Results:

• Successfully generated coffee rings on superslippery surfaces by dynamically creating contact line pinning defects.
• Established a linear relationship between coffee-ring diameter and target analyte concentration for quantitative detection.
• Demonstrated naked-eye detection of streptavidin and *Escherichia coli* over a wide range of concentrations.

Conclusions:

• This study presents the first use of superslippery surfaces to dynamically induce coffee-ring formation for detection.
• The developed method offers a user-friendly, visual, and interpretable approach for analyte detection.
• The strategy holds significant potential for point-of-care testing applications.