title: One-way wicking in open micro-channels controlled by channel topography.
abstract: One-way wicking (microfluidic diode) behaviors of a range of IPA-water mixtures on internally structured PDMS-based open micro-channels were experimentally demonstrated and quantified. The open microfluidic channels, each internally decorated with an array of angled fin-like-structure pairs, were fabricated using a combined photolithography and soft molding procedure. Propagations of wetting fluids were found to be much more impeded on the fin-tilting direction, or the hard wicking direction, comparing to the opposite direction, or the easy wicking direction. This asymmetric wicking behaviors were attributed to the structure-induced direction-dependent Laplace pressure. Two key parameters - the contact angle of the wicking fluid and the tilting angle of the fin-like structures - were studied. The effects of preferential evaporation and wetting instability were also investigated. The findings of this study are expected to provide a better understanding of how fluids interact with micro-scaled structures and to offer a new way of manipulating fluids at the micron and nanometer scales.
authors.affiliation: Department of Physics, University of Massachusetts, Amherst, MA, United States.
authors.forename: Jiansheng
authors.initials: J
authors.lastname: Feng
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Rothstein
mesh_terms: D046210:Microfluidic Analytical Techniques; D011312:Pressure; D012212:Rheology / Q000295:instrumentation / Q000379:methods*