Drop Impact Study on Flexible Superhydrophobic Surface Containing Micro-Nano Hierarchical Structures

Authors: Abinash Tripathy, Girish Muralidharan, Amitava Pramanik, Prosenjit Sen

Abstract:

Superhydrophobic surfaces are abundant in nature. Several surfaces such as wings of butterfly, legs of water strider, feet of gecko and the lotus leaf show extreme water repellence behaviour. Self-cleaning, stain-free fabrics, spill-resistant protective wears, drag reduction in micro-fluidic devices etc. are few applications of superhydrophobic surfaces. In order to design robust superhydrophobic surface, it is important to understand the interaction of water with superhydrophobic surface textures. In this work, we report a simple coating method for creating large-scale flexible superhydrophobic paper surface. The surface consists of multiple layers of silanized zirconia microparticles decorated with zirconia nanoparticles. Water contact angle as high as 159±1⁰ and contact angle hysteresis less than 8⁰ was observed. Drop impact studies on superhydrophobic paper surface were carried out by impinging water droplet and capturing its dynamics through high speed imaging. During the drop impact, the Weber number was varied from 20 to 80 by altering the impact velocity of the drop and the parameters such as contact time, normalized spread diameter were obtained. In contrast to earlier literature reports, we observed contact time to be dependent on impact velocity on superhydrophobic surface. Total contact time was split into two components as spread time and recoil time. The recoil time was found to be dependent on the impact velocity while the spread time on the surface did not show much variation with the impact velocity. Further, normalized spreading parameter was found to increase with increase in impact velocity.

Keywords: Contact angle, contact angle hysteresis, contact time, superhydrophobic.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1125171

References:

[1] Brown, P. S.; Bhushan, B. Designing bioinspired superoleophobic surfaces. APL Mater. 2016, 4 (1).
[2] Tuteja, A.; Choi, W.; Mabry, J. M.; McKinley, G. H.; Cohen, R. E. Robust omniphobic surfaces. Proc. Natl. Acad. Sci. U. S. A. 2008, 105 (47), 18200-18205.
[3] Tuteja, A.; Choi, W.; Ma, M.; Mabry, J. M.; Mazzella, S. A.; Rutledge, G. C.; McKinley, G. H.; Cohen, R. E. Designing superoleophobic surfaces. Science 2007, 318 (5856), 1618-1622.
[4] Barthlott, W.; Neinhuis, C. Purity of the sacred lotus, or escape from contamination in biological surfaces. PLANTA 1997, 202 (1), 1-8.
[5] Bird, J. C.; Dhiman, R.; Kwon, H.-M.; Varanasi, K. K. Reducing the contact time of a bouncing drop. Nature 2013, 503 (7476), 385-388.
[6] Bartolo, D.; Josserand, C.; Bonn, D. Retraction dynamics of aqueous drops upon impact on non-wetting surfaces. J. Fluid Mech. 2005, 545, 329-338.
[7] Clanet, C.; Béguin, C.; Richard, D.; Quéré, D, D. Maximal deformation of an impacting drop. J. Fluid Mech. 2004, 517, 199-208.
[8] Okumura, K.; Chevy, F.; Richard, D.; Quéré, D,; Clanet, C. Water spring: A model for bouncing drops. Europhys. Lett. 2003, 62 (2), 237-243.
[9] Richard, D.; Quéré, D,. Bouncing water drops. Europhys. Lett. 2000, 50 (6), 769-775.
[10] Richard, D.; Clanet, C.; Quéré, D,. Surface phenomena: Contact time of a bouncing drop. Nature 2002, 417 (6891), 811.
[11] Zhang, X.; Guo, Y.; Chen, H.; Zhu, W.; Zhang, P. A novel damage-tolerant superhydrophobic and superoleophilic material. J. Mater. Chem. A 2014, 2 (24), 9002-9006.
[12] Wong, T.-S.; Kang, S. H.; Tang, S. K. Y.; Smythe, E. J.; Hatton, B. D.; Grinthal, A.; Aizenberg, J. Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity. Nature 2011, 477 (7365), 443-447.
[13] Nosonovsky, M. Slippery when wetted. Nature 2011, 477 (7365), 412-413.
[14] Federle, W.; Barnes, W. J. P.; Baumgartner, W.; Drechsler, P.; Smith, J. M. Wet but not slippery: Boundary friction in tree frog adhesive toe pads. J. R. Soc. Interface 2006, 3 (10), 689-697.