Automated device for multi-stage paper-based assays enabled by an electroosmotic pumping valve.

Area of Science:

• Microfluidics
• Biotechnology
• Materials Science

Background:

• Paper-based devices offer low-cost platforms for diagnostics.
• Controlling fluid flow in paper-based devices is crucial for multi-step assays.
• Existing methods for flow control can be complex or expensive.

Purpose of the Study:

• To develop a controllable valve for paper-based devices using electroosmotic flow and a hydrophobic air gap.
• To enable finite dosing and continuous flow modes for multi-step assays.
• To demonstrate a low-cost, automated diagnostic device for pathogen detection.

Main Methods:

• Utilized electroosmotic flow generation in porous media to actuate a valve.
• Incorporated a hydrophobic air gap between paper pads to create a normally closed valve.
• Developed a model for flow dynamics and governing parameters, validated with experimental results.
• Designed an automated device integrating paper pads with printed circuit boards (PCBs).

Main Results:

• Demonstrated a controllable valve operating in finite dosing or continuous flow modes.
• Achieved stable valve operation under strenuous conditions with good model-experiment agreement.
• Successfully applied the device for SARS-CoV-2 sequence amplification from raw saliva samples using loop-mediated isothermal amplification (LAMP).

Conclusions:

• The developed valve provides a robust and controllable fluidic interface for paper-based devices.
• The integrated PCB-based device offers a straightforward design for automated, low-cost diagnostics.
• This approach holds promise for sensitive pathogen detection, such as SARS-CoV-2, directly from clinical samples.