Precise capillary flow for paper-based viscometry
The imbibition dynamics of aqueous solutions in paper substrates determines the performance of all the operations integrated in analytical paper-based devices. In particular, an accurate control of the flow rate is required for quantitative analysis such as viscometry. This work experimentally investigates paper filling dynamics in order to find a strategy to improve the precision and predictability of the imbibition process. The effect of performing successive wetting–drying cycles on the same strips is explored, since we have discovered that, after around four cycles, the filling kinematics is highly repetitive, and data closely follow the theoretical Lucas–Washburn model. It is found that the cyclic process enables quantitative assessment of the filling dynamics with uncertainties lower than 0.8 %. Implementing this protocol, paper-based viscometry with a precision around 1 % was experimentally demonstrated. This knowledge is of interest to develop paper-based microfluidic devices with a new level of precision.
KeywordsPaper-based microfluidics Capillary filling Viscometry
The authors thank the financial support received from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Universidad Nacional del Litoral (UNL), Argentina.
- Fassenden RW (1928) The viscosity and surface tension of dispersions of sucrose, lactose, skim milk powder, and butterfat. http://scholarworks.umass.edu/theses/1503/
- Liu Z, Hu J, Zhao Y, Qu Z, Xu F (2015) Experimental and numerical studies on liquid wicking into filter papers for paper-based diagnostics. Appl Therm Eng 88: 280–287. 10.1016/j.applthermaleng.2014.09.057, http://www.sciencedirect.com/science/article/pii/S1359431114008291
- Lucas R (1918) Ueber das zeitgesetz des kapillaren aufstiegs von flüssigkeiten. Colloid Polym Sci 23(1):15–22Google Scholar
- Masoodi R, Pillai KM (2010) Darcy’s law-based model for wicking in paper-like swelling porous media. AIChE J 56(9):2257–2267Google Scholar
- Shou D, Fan J (2015) The fastest capillary penetration of power-law fluids. Chem Eng Sci 137: 583–589. 10.1016/j.ces.2015.07.009, http://www.sciencedirect.com/science/article/pii/S0009250915004947
- Swindells JF, Snyder CF, R.C.H, Golden PE (1958) Viscosities of sucrose solutions at various temperatures: Tables of recalculated values. Technical report, National Bureau of StandardsGoogle Scholar