Transpiration-based micropump for delivering continuous ultra-low flow rates

Abstract

In this paper we describe the design, construction and operation of a micropump that delivers continuous, ultra-low flow velocities at 100 m s -1 . The pumping concept is based on the commonly observed phenomenon of transpiration in plant leaves. A liquid meniscus is pinned inside a microchannel by selective hydrophobic patterning and the evaporation rate of the liquid at the meniscus is controlled. The controlled evaporative flux results in a regulated flow of the liquid from a reservoir to the meniscus. Using this technique, precise flow control (5 nl min -1 ) has been achieved in several channel geometries for extended periods of time (2 h). Various factors affecting the performance of the pump were studied and theoretical predictions along with experimental results are presented. Such a micropump could find applications in emerging biological assays such as single-molecule studies of DNA and cell adhesion analyses.