A Magnetically Actuated Superhydrophobic Ratchet Surface for Droplet Manipulation

ChangHee Son, BingQiang Ji, JunKyu Park, Jie Feng, Seok Kim

Research output: Contribution to journalArticlepeer-review


A water droplet dispensed on a superhydrophobic ratchet surface is formed into an asymmetric shape, which creates a Laplace pressure gradient due to the contact angle difference between two sides. This work presents a magnetically actuated superhydrophobic ratchet surface composed of nanostructured black silicon strips on elastomer ridges. Uniformly magnetized NdFeB layers sputtered under the black silicon strips enable an external magnetic field to tilt the black silicon strips and form a superhydrophobic ratchet surface. Due to the dynamically controllable Laplace pressure gradient, a water droplet on the reported ratchet surface experiences different forces on two sides, which are explored in this work. Here, the detailed fabrication procedure and the related magnetomechanical model are provided. In addition, the resultant asymmetric spreading of a water droplet is studied. Finally, droplet impact characteristics are investigated in three different behaviors of deposition, rebound, and penetration depending on the impact speed. The findings in this work are exploitable for further droplet manipulation studies based on a dynamically controllable superhydrophobic ratchet surface.
Original languageEnglish (US)
Article number325
Issue number3
StatePublished - Mar 19 2021


  • Droplet manipulation
  • Laplace pressure
  • NdFeB
  • Ratchet surface
  • Superhydrophobic

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Mechanical Engineering
  • Electrical and Electronic Engineering


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