Multifunctional analytical platform on a paper strip: separation, preconcentration, and subattomolar detection

Area of Science:

• Plasmonics
• Analytical Chemistry
• Materials Science
• Nanotechnology

Background:

• Paper-based analytical devices (PADs) offer low-cost, portable sensing solutions.
• Enhancing sensitivity and handling complex samples remain key challenges for PADs.
• Surface-enhanced Raman scattering (SERS) provides high sensitivity for molecular detection.

Purpose of the Study:

• To develop a novel plasmonic paper-based analytical platform (μPAD) with enhanced sensitivity and functional versatility.
• To achieve ultrasensitive detection of analytes in complex samples using a lithography-free approach.
• To investigate a new microfluidic design for efficient sample handling and analyte preconcentration.

Main Methods:

• Fabrication of a starlike-shaped microfluidic paper-based analytical device (μPAD) using a simple cut-and-drop method (lithography-free).
• Creation of a surface chemical gradient via differential polyelectrolyte coating for complex sample separation.
• Utilized surface-enhanced Raman scattering (SERS) as the transduction method for signal amplification.

Main Results:

• Achieved a highly versatile plasmonic platform with a subattomolar (<10⁻¹⁸ M) detection limit.
• Demonstrated efficient liquid handling and analyte preconcentration through capillary-driven flow in a single cellulose microfiber.
• Successfully separated components of complex samples using the engineered surface chemical gradient.

Conclusions:

• The developed plasmonic μPAD offers a simple, cost-effective, and ultrasensitive analytical tool.
• The lithography-free design and unique fluidic handling enable broad applicability for complex sample analysis.
• This platform represents a significant advancement in portable and high-performance point-of-care diagnostics.