Capillary flow in microchannels

Abstract

The surface of microchannels, especially polymer channels, often needs to be treated to acquire specific properties. This study investigated the capillary flow and the interface behavior in several glass capillaries and fabricated microchannels using a photographic technique and image analysis. The effect of air plasma treatment on the characteristics of capillary flow in three types of microfluidic chips, and the longevity of the acquired surface properties were also studied. It was observed that the dynamic contact angles in microchannels were significantly larger than those measured from a flat substrate and the angle varied with channel size. This suggests that dynamic contact angle measured in situ must be used in the theoretical calculation of capillary flow speed, especially for microfabricated microchannels since the surface properties are likely to be different from the native material. This study also revealed that plasma treatment could induce different interface patterns in the PDMS channels from those in the glass and PC channels. The PDMS channel walls could acquire different level of hydrophilicity during the plasma treatment, and the recovery to hydrophobicity is also non-homogeneous.

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

“…Strage et al, 2003), rectangular (e.g. Ichikawa et al, 2004;Jong et al, 2007;Zhu and Petkovic-Duran, 2010) and grooved/triangular (Yost and Holm, 1995;Romero and Yost, 2006;Baret et al, 2007). Moreover, the same approach has been taken for channels defined by hydrophilic paths on a hydrophobic substrate (Darhuber et al, 2001) and by the space between two parallel plates (Rosendahl et al, 2004) under the assumption of flow with low Reynolds number and liquid imbibing in a tube/slablike manner.…”

Development and characterisation of integrated microfluidics on waveguide-based photonic platforms fabricated from hybrid materials

“…Surface modification was done via oxygen plasma treatment in order to increase the wettability of the surfaces. It is well-known that hydrophilic channel surfaces are desirable for applications in microfluidics as they support pump-free fluid flow under capillary action (Zhu and Petkovic-Duran 2010). Surfaces were modified by exposure to oxygen plasma for 5 min (Harrick Plasma PDC-002, 30 W, 0.1 Torr O 2 , 3 sccm).…”

Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane) Microstructures with Velocity-Dependent Contact Angles

“…The velocity fields near the interface were in good agreement with fluid mechanics and molecular dynamics studies. The dynamic contact angle in a microchannel could be larger (advancing) or smaller (receding) than the static contact angle [22]. In all of the aforementioned studies, the effects of the relationship between the contact angle and the contact line velocity on the flow characteristics inside the microchannel or microchamber were not investigated.…”