Enhancing Fluid Absorption Time Delays Through Glycerol Concentration Variations in Microfluidic Paper-Based Systems

Paper-based microfluidics provides an economical and flexible approach to fluid handling for simple and complex assays. Many applications still require ease of flow control with the added advantage of low-cost fabrication for commercial applications. In this study, we develop a fluid control strategy using glycerol as a barrier within paper channels. Glycerol reduces porosity and increases resistance, causing delayed flow times. As glycerol is hydrophilic in nature and can establish hydrogen bonds with water molecules, it is an efficient substrate for creating these delay zones in paper strips. The Lucas–Washburn model describes the physics for flow of liquid water through the porous substrate. From our findings, we observed that the water flow time was delayed from 5 to 20 min and penetration reduced from 43 mm to 24 mm by increasing glycerol concentration from 0% to 30%. Using oleic acid (fatty acid) as the working fluid instead of water extended the delay further, causing it to take up to 1 day to transport 35 mm with 30% glycerol investigation into the effects of glycerol concentration on flow behavior highlights the importance of understanding absorption time delays and the physics of wet-out flow in porous media., and we hope that, ultimately, our findings will be applicable for a variety of paper-based microfluidic devices for commercial applications