Wax Spreading in Paper under Controlled Pressure and Temperature

Area of Science:

• Microfluidics
• Materials Science
• Biotechnology

Background:

• Paper-based microfluidic devices offer low-cost diagnostics.
• Current fabrication methods can be slow or lack high resolution.
• Controlling wax penetration and spreading is crucial for device performance.

Purpose of the Study:

• To develop a rapid, high-resolution fabrication method for paper-based microfluidic devices.
• To investigate the influence of temperature and pressure on wax penetration and lateral spreading.
• To establish optimal printing conditions for device fabrication.

Main Methods:

• Utilized wax-ink-based printing with asymmetric heating and applied pressure.
• Systematically varied temperature (up to 110 °C) and pressure (up to 49 kPa).
• Analyzed wax line width, paper penetration depth, and compared results with the Lucas-Washburn equation.

Main Results:

• Achieved high-resolution patterns with narrow lateral spreading (down to 90 μm from 130 μm initial width).
• Demonstrated thorough wax penetration through 190 μm-thick paper.
• Identified temperature's effect on spreading due to wax viscosity changes.
• Observed pressure's deviation from Lucas-Washburn due to paper compression.

Conclusions:

• Optimized conditions for full wax penetration with minimal lateral spreading were identified.
• The developed method enables rapid, high-resolution fabrication of paper-based devices.
• Findings support potential for roll-to-roll manufacturing of paper-based diagnostic devices.