Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding?

Dong, Jian; Guo, Youhai; Jiao, Long; Si, Chao; Bian, Yinbo; Zhang, Zheng; Hu, Jianliang

doi:10.3390/app11093734

Open AccessArticle

Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding?

by

Jian Dong

^1,2,*

,

Youhai Guo

¹

,

Long Jiao

¹,

Chao Si

¹,

Yinbo Bian

¹,

Zheng Zhang

¹ and

Jianliang Hu

¹

Key Laboratory of E&M, Zhejiang University of Technology, Ministry of Education & Zhejiang Province, Hangzhou 310023, China

²

State Key Lab of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China

^*

Author to whom correspondence should be addressed.

Appl. Sci. 2021, 11(9), 3734; https://doi.org/10.3390/app11093734

Submission received: 25 March 2021 / Revised: 16 April 2021 / Accepted: 18 April 2021 / Published: 21 April 2021

(This article belongs to the Special Issue Physics and Mechanics of New Materials and Their Applications 2020)

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Abstract

The motion state of a droplet on an inclined, hydrophilic rough surface in gravity, pinned or sliding, is governed by the balance between the driving and the pinned forces. It can be judged by the droplet’s shape on the inclined hydrophilic rough surface and the droplet’s contact angle hysteresis. In this paper, we used the minimum energy theory, the minimum energy dissipation theory, and the nonlinear numerical optimization algorithm to establish Models 1–3 to calculate out the advancing/receding contact angles (

θ_{a}

/

θ_{r}

), the initial front/rear contact angles (

θ_{1 - 0}

/

θ_{2 - 0}

) and the dynamic front/rear contact angles (

θ_{1 - *}

/

θ_{2 - *}

) for a droplet on a rough surface. Also, we predicted the motion state of the droplet on an inclined hydrophilic rough surface in gravity by comparing

θ_{1 - 0}

(

θ_{2 - 0}

) and

θ_{1 - *}

(

θ_{2 - *}

) with

θ_{a}

(

θ_{r}

). Experiments were done to verify the predictions. They showed that the predictions were in good agreement with the experimental results. These models are promising as novel design approaches of hydrophilic functional rough surfaces, which are frequently applied to manipulate droplets in microfluidic chips.

Keywords: droplet; inclined hydrophilic rough surface; pinned; sliding; droplet shape; droplet contact angle hysteresis

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MDPI and ACS Style

Dong, J.; Guo, Y.; Jiao, L.; Si, C.; Bian, Y.; Zhang, Z.; Hu, J. Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding? Appl. Sci. 2021, 11, 3734. https://doi.org/10.3390/app11093734

AMA Style

Dong J, Guo Y, Jiao L, Si C, Bian Y, Zhang Z, Hu J. Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding? Applied Sciences. 2021; 11(9):3734. https://doi.org/10.3390/app11093734

Chicago/Turabian Style

Dong, Jian, Youhai Guo, Long Jiao, Chao Si, Yinbo Bian, Zheng Zhang, and Jianliang Hu. 2021. "Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding?" Applied Sciences 11, no. 9: 3734. https://doi.org/10.3390/app11093734

APA Style

Dong, J., Guo, Y., Jiao, L., Si, C., Bian, Y., Zhang, Z., & Hu, J. (2021). Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding? Applied Sciences, 11(9), 3734. https://doi.org/10.3390/app11093734

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Which Is the Motion State of a Droplet on an Inclined Hydrophilic Rough Surface in Gravity: Pinned or Sliding?

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