The Role of Paper Chemistry and Paper Manufacture in the Design of Paper-Based Diagnostics

Abstract

Paper has been used intensively for thousands of years, and it is a material made from renewable resources. It consists of a highly porous, bendable and foldable, flat structure of randomly arranged and connected fiber-like basic building blocks. The possibility to transport fluids without pumps and sophisticated dosing systems is attractive, and microfluidic paper for diagnostic applications has gained increasing interest, in particular, throughout the last decade. Although a number of interesting demonstrator devices for such easy-to-use diagnostic systems have been reported, still only a very limited number of devices made it into the market. The latter is mainly caused by the geometric and chemical complexity of the paper material itself. Whereas chemical functionalization (e.g., for defining hydrophobic barriers for spatially resolved fluid transport) is well advanced and will be covered by other groups in this book, understanding the impact of the paper material itself on the performance of paper-based diagnostic devices is still a challenge. Yet, only if we understand the latter from a fundamental point of view, more advanced and successful paper materials for such applications may become available. This book chapter outlines principles of paper manufacture; it thereafter reviews important paper chemistry aspects, and finally highlights recent developments on how engineering the morphology and chemistry of paper sheets gives us more insight into fundamentals on the role of the material itself in paper-based diagnostic applications.