The Influence of Cross-Sectional Shape and Orientation of Micropillar Surface on Microdroplet Formation by a Dewetting Process

Bambang Arip Dwiyantoro; Shiu-Wu Chau

doi:10.5614/j.eng.technol.sci.2013.45.2.5

Authors

Bambang Arip Dwiyantoro Department of Mechanical Engineering, Institute of Technology Sepuluh Nopember
Shiu-Wu Chau Department of Mechanical Engineering, National Taiwan University of Science and Techonology

DOI:

https://doi.org/10.5614/j.eng.technol.sci.2013.45.2.5

Abstract

In this study the dewetting process on micropillars of three different cross-sectional shapes, i.e. circular, square and triangular, was numerically investigated. The influence of the orientation of the triangular and square micropillars on the dewetting behavior was also studied. The numerical simulations showed that the cross-sectional shapes of the micropillars and their orientation play an important role in determining the flow pattern of the dewetting process, especially the evolution and movement of the meniscus across the micropillar before a microdroplet is formed. The diameter of the microdroplets is mainly determined by the capillary effect, viscous drag and fluid inertia contributed by the peeling rate and the thickness of the water layer above the micropillar. The numerical results also indicate that the hydraulic diameter of the micropillars (Dp) is one of the parameters governing the size of the microdroplets formed on the top surface of the micropillars after the dewetting process, while the microdroplet diameter is almost insensitive to the cross-sectional shape and orientation of the micropillars. The dimensionless diameter of the microdroplets (d) can then be expressed as a function of a dimensionless group, i.e. the Ohnesorge number (Oh), the capillary number (Ca), the dimensionless liquid thickness (H), and the contact angle (q).

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References

Sugiura, S., Nakajima, M. & Seki, M., Prediction of Droplet Diameter for Microchannel Emulsification, Langmuir, 18(10), pp. 3854-3859, 2002.

Xu, J.H., Luo, G.S., Chen, G.G. & Wang, J.D., Experimental and Theoretical Approaches on Droplet Formation from A Micrometer Screen Hole, Journal of Membrane Science, 266(1-2), pp. 121-131, 2005.

Gupta, A. & Kumar, R., Effect of Geometry on Droplet Formation in The Squeezing Regime in A Microfluidic T-Junction, Microfluid Nanofluid, 8(6), pp. 799-812, 2010.

Luo, C., Xing, R., Zhang, Z., Fu, J. & Han, Y., Ordered Droplet Formation by Thin Polymer Film Dewetting on A Stripe-Patterned Substrate, Journal of Colloid and Interface Science, 269(1), pp. 158-163, 2004.

Yoon, B., Acharya, H., Lee, G., Kim, H., Huh, J. & Park, C., Nanopatterning of Thin Polymer Films by Controlled Dewetting on A Topographic Pre-Pattern, Soft Matter, 4(1), pp. 1476-1472, 2008.

Mulji, N. & Chandra, S., Rupture and Dewetting of Water Films on Solid Surfaces, Journal of Colloid and Interface Science, 352(1), pp. 194-201, 2010.

Zhang, Z., Wang, Z., Xing, R. & Han, Y., How to Form Regular Polymer Microstructures by Surface-Pattern-Directed Dewetting, Surface Science, 539(1-3), pp. 129-136, 2003.

Martin, C.P., Blunt, M.O., Vaujour, E.P., Stannard, A. & Moriarty, P., Controlling Pattern Formation in Nanoparticle Assemblies via Directed Solvent Dewetting, Physical Review Letters, 99(11), 116103, pp. 1-4, 2007.

Reiter, G., Al Akhrass, S., Hamieh, M., Damman, P., Gabriele, S., Vilmin, T. & Rapha<

Karthaus, O., Mikami, S. & Hashimoto, Y., Control of Droplet Size and Spacing in Micrometer-Sized Polymeric Dewetting Patterns, Journal of Colloid and Interface Science, 301(2), pp.703-705, 2006.

Guan, J., Boukany, P.E., Hemminger, O., Chiou, N.R., Zha, W. & Lee, L.J., Large Laterally Ordered Nanochannel Arrays from DNA Combing and Imprinting, Advanced Materials, 22(36), pp. 3997-4001, 2010.

Lin, C.H., Guan, J., Chau, S.W., Chen, S.C. & Lee, L.J., Patterning Nanowire and Micro-/Nanoparticle Array on Micropillar-Structured Surface: Experiment and Modeling, Biomicrofluidics, 4(3), 034103, pp. 1-15, 2010.

Muzaferija, S., Adaptive Finite Volume Method for Flow Prediction Using Unstructured Meshes and Multigrid Approach, PhD Thesis, Department of Mechanical Engineering, University of London, 1994.

Khosla, P.K. & Rubin, S.G., A Diagonally Dominant Second-Order Accurate Implicit Scheme, Computers and Fluids, 2(2), pp. 207-209, 1974.

Pantankar, S.V., Numerical Heat Transfer and Fluid Flow, 1st edition, Hemisphere, pp. 30-70, 1980.

Lin, C.H., Guan, J., Chau, S.W. & Lee, L.J., Experimental and Numerical Analysis of DNA Nanostrand Array Formation by Molecular Combing on Microwell Patterned Surface, Journal of Physics D: Applied Physics, 42(2), 025303, pp.1-8, 2009.

PeriA, M. & Ferziger, J.H., Computational Methods for Fluid Dynamics, 1st edition, Springer, 25-50, 1996.

Dwiyantoro, B.A. & Chau, S.W., The Dynamic Behavior of Droplet Formation on Micropillar Surface During A Dewetting Process, 12th IEEE International Conference on Nanotechnology (IEEE-NANO), pp. 1-6, 2012.

De Gennes, P.G., Brochard-Wyart, F. & Quere, D., Capillarity and Wetting Phenomena, Springer, 2002.