Capillarity Driven Interface Motion in a Flat Triangular Minichannel

In microchannel flow, gas-liquid interface behavior is important for many applications, e.g. micro-reactors, micro heat pipes to name only two of them. Microfluidic channels shape are generally rectangular or triangular with associated solid corner. Those corners are interesting for they drastically increase capillary effects of wetting liquids compared to smooth solid boundaries. We study capillarity driven gas–liquid flows in a flat triangular channel. A channel of triangular cross section was micro-machined in a polymeric material and covered by a transparent plexiglas plate. The wetting fluid is injected at a controlled flow rate and the interface motion along the corners is recorded with a CCD video camera. A simple lubrication theory predicts the temporal evolution of the liquid-gas interface. A good agreement is found between those predictions and experimental results. the theory also predicts when the invasion of the channel bulk occurs. The dynamics of the bulk meniscus is discussed. The results suggest that the bulk meniscus dynamics is affected by the growth of the liquid fingers that develop along the edges of the channel.