Friction and Wetting Transitions of Magnetic Droplets on Micropillared Superhydrophobic Surfaces

Anas Al-Azawi, Mika Latikka, Ville Jokinen, Sami Franssila, Robin H.A. Ras*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

15 Citations (Scopus)
161 Downloads (Pure)


Reliable characterization of wetting properties is essential for the development and optimization of superhydrophobic surfaces. Here, the dynamics of superhydrophobicity is studied including droplet friction and wetting transitions by using droplet oscillations on micropillared surfaces. Analyzing droplet oscillations by high-speed camera makes it possible to obtain energy dissipation parameters such as contact angle hysteresis force and viscous damping coefficients, which indicate pinning and viscous losses, respectively. It is shown that the dissipative forces increase with increasing solid fraction and magnetic force. For 10 µm diameter pillars, the solid fraction range within which droplet oscillations are possible is between 0.97% and 2.18%. Beyond the upper limit, the oscillations become heavily damped due to high friction force. Below the lower limit, the droplet is no longer supported by the pillar tops and undergoes a Cassie–Wenzel transition. This transition is found to occur at lower pressure for a moving droplet than for a static droplet. The findings can help to optimize micropillared surfaces for low-friction droplet transport.

Original languageEnglish
Article number1700860
Pages (from-to)1-7
Issue number38
Publication statusPublished - 11 Oct 2017
MoE publication typeA1 Journal article-refereed


  • droplet oscillations
  • friction
  • superhydrophobicity
  • wetting transition


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