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Experiments in Fluids

, 60:169 | Cite as

Experimental investigation on water repellency and anisotropic wettability of microgrooved polymer surfaces

  • Daehee Kwon
  • Sangmin Lee
  • Eunseop YeomEmail author
Research Article
  • 94 Downloads

Abstract

Simple patterns on a surface can enhance water repellency and simultaneously impose directional wettability. Surfaces exhibiting periodic microscale grooves are examples of such surfaces. Here, we design microgrooved surfaces with three different groove widths and experimentally investigate their impact behaviors on the surfaces. In terms of wetting state, the robustness of water repellency against an impinging droplet is evaluated. Contact angle of a surface alone cannot represent the water repellency against impinging droplets. Surfaces with large contact angles are found to be less water repellent. However, water repellency of a surface depends on its capillary pressure, which resists the wetting state transition. The anisotropic pattern of grooves naturally affects the contact line motion of a droplet, particularly during the spreading and receding phases. Therefore, directional behaviors of the spreading and receding diameter and temporal characteristics were also experimentally examined. Temporal characteristics of smooth surfaces are nearly identical to those in the direction parallel to the grooved surface, while distinctive characteristics were observed in the perpendicular direction. This discrepancy probably originated from the discontinuity of the contact line experienced in the perpendicular direction.

Graphic abstract

List of symbols

C

Speed of sound inside drops (m s−1)

D

Diameter of droplets (mm)

Oh

Ohnesorge number

PC

Capillary pressure (kPa)

PD

Dynamic pressure (kPa)

PWH

Water hammer pressure (kPa)

Pwet

Wetting pressure (kPa)

V

Impact speed (m s−1)

We

Weber number

b

Ridge width (μm)

h

Groove depth (μm)

k

Empirical constant for water hammer pressure

lC

Capillary length (mm)

r

Roughness factor

ts

Spreading time (ms)

w

Groove width (μm)

β

Spreading factor

θ

Contact angle (°)

μ

Viscosity (mPa s)

ρ

Density (kg m−3)

σ

Surface tension (mN m−1)

ϕ

Texture area fraction

Notes

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (NRF-2019R1H1A1079157).

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Corporate Research and Development CenterSamsung Electro-mechanicsSuwon-siRepublic of Korea
  2. 2.Division of Mechanical Automotive, Robot Components Engineering (Automotive Major)Dong-Eui UniversityBusanRepublic of Korea
  3. 3.School of Mechanical EngineeringPusan National UniversityBusanRepublic of Korea

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