Paper-based microfluidics has gained an increasing interest as a platform for easy-to-use, point-of-care diagnostics, food quality control or further analytical devices. With respect to the latter, a number of recent studies aim on the development of low-cost, simple fabrication techniques and the use of accurate and efficient detection methods. Present examples have in common that off-the-shelf (filter) paper is being used, channels are designed by physical blocking of pores using wax, and detection elements are often physisorbed to the paper fibers. Limitations that occur from such a design are chemically and thermally instable barrier and sensor functions, as well as non-trivial to control capillary flow.<br/>In this contribution, I will in particular show that a combination of paper engineering processes with tailored surface-immobilization of (functional) polymers, address the above mentioned limitations. Lab-engineered paper sheets, consisting of different fiber sources (e.g. eucalyptus, cotton linters) and varying porosities were prepared and small, millimeter-sized channels were defined inside the paper sheets by covalently attaching hydrophobic polymers on the fiber surface. Very small amount of polymer mass (less than 2 wt% with respect to total mass of the functional paper sheets) attached to the fibers is sufficient to completely change wetting characteristics and to guide an aqueous fluid by capillary forces inside polymer-defined paper channels. The capillary-driven fluid flow of an aqueous solution inside the channels is a function of the fiber source, paper sheet porosity and channel width, the latter being defined by the hydrophobic barriers. As such this flow can be reproducibly tailored over a wide range by simple to adjust, intrinsic paper properties (Figure). Further concepts that will be highlighted include the spatially definition of reaction/detection zones prepared on paper, which are useful to carry out cascade model reactions inside the channels, and the use of such functional microfluidic paper substrates as simple colorimetric sensor devices.

Microfluidic paper - influence of fiber source, sheet properties and fiber surface modification on capillary driven flow

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.