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Article

A Magnetically Actuated Superhydrophobic Ratchet Surface for Droplet Manipulation

by 1,†, 1,†, 1,†, 1 and 1,2,*
1
Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
2
Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 37673, Korea
*
Author to whom correspondence should be addressed.
ChangHee Son, Bingqiang Ji and Jun Kyu Park contributed equally to this work.
Academic Editor: Giampaolo Mistura
Micromachines 2021, 12(3), 325; https://doi.org/10.3390/mi12030325
Received: 3 March 2021 / Revised: 15 March 2021 / Accepted: 17 March 2021 / Published: 19 March 2021
(This article belongs to the Section E:Engineering and Technology)
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. View Full-Text
Keywords: ratchet surface; superhydrophobic; Laplace pressure; droplet manipulation; NdFeB ratchet surface; superhydrophobic; Laplace pressure; droplet manipulation; NdFeB
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MDPI and ACS Style

Son, C.; Ji, B.; Park, J.; Feng, J.; Kim, S. A Magnetically Actuated Superhydrophobic Ratchet Surface for Droplet Manipulation. Micromachines 2021, 12, 325. https://doi.org/10.3390/mi12030325

AMA Style

Son C, Ji B, Park J, Feng J, Kim S. A Magnetically Actuated Superhydrophobic Ratchet Surface for Droplet Manipulation. Micromachines. 2021; 12(3):325. https://doi.org/10.3390/mi12030325

Chicago/Turabian Style

Son, ChangHee, BingQiang Ji, JunKyu Park, Jie Feng, and Seok Kim. 2021. "A Magnetically Actuated Superhydrophobic Ratchet Surface for Droplet Manipulation" Micromachines 12, no. 3: 325. https://doi.org/10.3390/mi12030325

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