Journal of the Korean Society of Visualization (한국가시화정보학회지)

The Korean Society of Visualization (한국가시화정보학회)
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Spreading and retraction dynamics of a liquid droplet impacting rough hydrophobic surfaces: Formation of micrometer-sized drops

거친 발수 표면에 충돌하는 유체 방울의 팽창 및 수축 역학: 미세 유체 방울의 형성

  • Kim, Uijin (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology) ;
  • Kim, Jeong-Hyun (Department of Mechanical System Design Engineering, Seoul National University of Science and Technology)
  • Received : 2021.07.18
  • Accepted : 2021.09.27
  • Published : 2021.12.31
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Abstract

In this study, we investigated the dynamics of a droplet impacting rough hydrophobic surfaces through high-speed imaging. Micrometer-sized structures with grooves and pillars were fabricated on smooth Polydimethylsiloxane (PDMS) surfaces by laser ablation. We used Newtonian and non-Newtonian liquid droplets to study the drop impact dynamics. De-ionized water and aqueous glycerin solutions were used for the Newtonian liquid droplet. The solutions of xanthan gum in water were prepared to provide elastic property to the Newtonian droplet. We found that the orientation of the surface structures affected the maximal spreading diameter of the droplet due to the degree of slippage. During the droplet retraction, the dynamic receding contact angles were measured to be around 90° or less. It resulted in the formation of the micro-capillary bridges between the receding droplet and the surface structures. Then, the rupture of the capillary bridge led to the formation of micrometer-sized droplets on top of the surface structures. The size of the microdroplets was found to increase with increasing the impacting velocity and viscosity of the Newtonian liquid droplets. However, the size of the isolated microdroplets decreased with enhancing the elasticity of the droplets, and the size of the non-Newtonian microdroplets was not affected by the impacting velocity.

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Acknowledgement

이 연구는 서울과학기술대학교 교내 일반과제 연구비 지원으로 수행되었습니다.

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