Micromachines 2014, 5(2), 116-138; doi:10.3390/mi5020116
Article

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

Received: 6 January 2014; in revised form: 15 March 2014 / Accepted: 19 March 2014 / Published: 25 March 2014
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS) microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented.
Keywords: microfluidics; dynamic contact angle; gas-liquid interface; surface tension; filling process
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MDPI and ACS Style

Chen, J.J.; Liao, S.C.; Liu, M.H.; Lin, J.D.; Sheu, T.S.; Miao, M., Jr. Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane) Microstructures with Velocity-Dependent Contact Angles. Micromachines 2014, 5, 116-138.

AMA Style

Chen JJ, Liao SC, Liu MH, Lin JD, Sheu TS, Miao M, Jr. Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane) Microstructures with Velocity-Dependent Contact Angles. Micromachines. 2014; 5(2):116-138.

Chicago/Turabian Style

Chen, Jyh J.; Liao, Shih C.; Liu, Mao H.; Lin, Jenn D.; Sheu, Tsung S.; Miao, Ming, Jr. 2014. "Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane) Microstructures with Velocity-Dependent Contact Angles." Micromachines 5, no. 2: 116-138.

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