Microfluidic paper analytical devices (μPADs) offer a safe, user-friendly, and cost-effective platform for inquiry-based laboratory experiments, but fabricating these devices is often tedious and time consuming. Previously, wax printing was a preferred paper device fabrication method, but since wax printers are no longer commercially available, alternative methods are needed. This presentation highlights one such alternative, the air-gap PAD, and its use in the teaching laboratory. The air-gap PAD consists of hydrophilic paper zones, separated by “air gaps” and affixed to a hydrophobic backing with double-sided adhesive. The primary appeal of this design is its compatibility with roll-to-roll manufacturing equipment for large-scale production. Here, we report on a pilot production run of air-gap “titrator” devices in partnership with a local test strip manufacturer, as well as their use in a paper-microfluidics-based acid-base titration experiment by students in a group of California high schools. Figure 1 shows titration curves obtained from RGB analysis of paper-based titrations performed on both the original wax-printed titrators and the new air-gap design. This air-gap PAD design provides a scalable manufacturing method for widespread deployment of paper microfluidics in the educational laboratory, and it will be applicable for some research applications that are currently fabricated with wax printing technology.

“Air-gap” paper microfluidic devices for acid-base titrations in the educational laboratory

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