Paper-Based Microfluidics: Fabrication Technique and Dynamics of Capillary-Driven Surface Flow
mediaposted on 26.11.2014, 00:00 by Joel Songok, Mikko Tuominen, Hannu Teisala, Janne Haapanen, Jyrki Mäkelä, Jurkka Kuusipalo, Martti Toivakka
Paper-based devices provide an alternative technology for simple, low-cost, portable, and disposable diagnostic tools for many applications, including clinical diagnosis, food quality control, and environmental monitoring. In this study we report a two-step fabrication process for creating two-dimensional microfluidic channels to move liquids on a hydrophobized paper surface. A highly hydrophobic surface was created on paper by TiO2 nanoparticle coating using a high-speed, roll-to-roll liquid flame spray technique. The hydrophilic pattern was then generated by UV irradiation through a photomask utilizing the photocatalytic property of TiO2. The flow dynamics of five model liquids with differing surface tensions 48–72 mN·m–1 and viscosities 1–15 mN·m–2 was studied. The results show that the liquid front (l) in a channel advances in time (t) according to the power law l = Zt0.5 (Z is an empirical constant which depend on the liquid properties and channel dimensions). The flow dynamics of the liquids with low viscosity show a dependence on the channel width and the droplet volume, while the flow of liquids with high viscosity is mainly controlled by the viscous forces.