Abstract
Since the pioneering works of Wenzel and Cassie Baxter in the 1930s, and now with the trivialization of the micro- and nanotechnology facilities, superhydrophobic surfaces have been announced as potentially amazing components for applications such as fluidic, optical, electronic, or thermal devices. In this paper, we show that using superhydrophobic surfaces in digital microfluidic devices could solve some usual limitations or enhance their performances. Thus, we investigate a specific monophasic (air environment) microfluidic device based on electrowetting integrating either a hydrophobic or a superhydrophobic surface as a counter-electrode. The droplet transport using a superhydrophobic surface compared with a classical hydrophobic system led to some original results. Characterization of the dynamic contact angle and the droplet shape allows us to get new insight of the fluid dynamics. Among the remarkable properties reported, a 30 % lower applied voltage, a 30 % higher average speed with a maximum instantaneous speed of 460 mm/s have been measured. Furthermore, we have noticed a huge droplet deformation leading to an increase by a factor 5 of the Weber number (from 1.4 to 7.0) on SH compared to hydrophobic surfaces. Finally, we discuss some of the repercussions of this behaviour especially for microfluidic device.
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Acknowledgments
The Centre National de la Recherche Scientifique (CNRS), the Defence Science and Technology Laboratory (Porton Down, United Kingdom) and the European Community Seventh Frame-work Programme (FP7/2007–2013) under grant agreement no. 227243 are gratefully acknowledged for financial support. The authors thank F. Zoueshtiagh and P. Brunet for their kind support during the visualizations and G. Piret for her kind support for superhydrophobic surfaces realization.
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Lapierre, F., Jonsson-Niedziolka, M., Coffinier, Y. et al. Droplet transport by electrowetting: lets get rough!. Microfluid Nanofluid 15, 327–336 (2013). https://doi.org/10.1007/s10404-013-1149-1
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DOI: https://doi.org/10.1007/s10404-013-1149-1