title: Capillary Pumping Independent of Liquid Sample Viscosity.
abstract: Capillary flow is a dominating liquid transport phenomenon on the micro- and nanoscale. As described at the beginning of the 20th century, the flow rate during imbibition of a horizontal capillary tube follows the Washburn equation, i.e., decreases over time and depends on the viscosity of the sample. This poses a problem for capillary driven systems that rely on a predictable flow rate and where the liquid viscosity is not precisely known. Here we introduce and successfully experimentally verify the first compact capillary pump design with a flow rate constant in time and independent of the liquid viscosity that can operate over an extended period of time. We also present a detailed theoretical model for gravitation-independent capillary filling, which predicts the novel pump performance to within measurement error margins, and in which we, for the first time, explicitly identify gas inertia dominated flow as a fourth distinct flow regime in capillary pumping. These results are of potential interest for a multitude of applications and we expect our results to find most immediate applications within lab-on-a-chip systems and diagnostic devices.
authors: KTH Royal Institute of Technology, Micro and Nanosystems, Osquldas väg 10, 100 44 Stockholm, Sweden.
authors: Weijin
authors: W
authors: Guo
authors: KTH Royal Institute of Technology, Micro and Nanosystems, Osquldas väg 10, 100 44 Stockholm, Sweden.
authors: Jonas
authors: J
authors: Hansson
authors: KTH Royal Institute of Technology, Micro and Nanosystems, Osquldas väg 10, 100 44 Stockholm, Sweden.
authors: Wouter
authors: W
authors: van der Wijngaart