The sliding mode and dissipative force of moving nanodroplets on smooth and striped hydrophobic surfaces

Lyu, Shuhang; Yang, Zhen; Duan, Yuanyuan

doi:10.1016/j.molliq.2021.118284

Cited by 6 publications

(2 citation statements)

References 48 publications

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“…At the interface between the droplet and the brush, the velocity is small indicating that the droplet rolls with little to no sliding even in the presence of lubricant. This is different from previous simulations of polymer droplets on hard corrugated substrates, , where significant slip was observed at the surface.…”

Section: Results and Discussioncontrasting

confidence: 99%

“…The friction results from an interplay of energy dissipation at the adhesive surface (contact area dissipation), at the contact line, i.e., the wetting ridge (contact line dissipation), and inside the droplet (bulk dissipation). In previous molecular simulation studies of droplets driven by external forces moving on flat or patterned forces, it was found that droplets may both roll and slide (slip) at the surface. ,, In such cases, it has been argued that the friction between the droplet and the surface is dominated by contact area dissipation for small droplet sizes , and by contact line friction or bulk dissipation for larger droplets. In our system, we find that the flow velocity is very small at the interface between droplet and substrate; thus, the droplet does not slide, and the dissipation at the adhesive surface can be neglected.…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of Droplets Moving on Lubricated Polymer Brushes

Badr,

Hauer,

Vollmer

et al. 2024

Langmuir

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Understanding the dynamics of drops on polymercoated surfaces is crucial for optimizing applications such as selfcleaning materials or microfluidic devices. While the static and dynamic properties of deposited drops have been well characterized, a microscopic understanding of the underlying dynamics is missing. In particular, it is unclear how drop dynamics depends on the amount of uncross-linked chains in the brush, because experimental techniques fail to quantify those. Here we use coarse-grained simulations to study droplets moving on a lubricated polymer brush substrate under the influence of an external body force. The simulation model is based on the many body dissipative particle dynamics (MDPD) method and designed to mimic a system of water droplets on poly(dimethylsiloxane) (PDMS) brushes with chemically identical PDMS lubricant. In agreement with experiments, we find a sublinear power law dependence between the external force F and the droplet velocity v, F ∝ v α with α < 1; however, the exponents differ (α ∼ 0.6−0.7 in simulations versus α ∼ 0.25 in experiments). With increasing velocity, the droplets elongate and the receding contact angle decreases, whereas the advancing contact angle remains roughly constant. Analyzing the flow profiles inside the droplet reveals that the droplets do not slide but roll, with vanishing slip at the substrate surface. Surprisingly, adding lubricant has very little effect on the effective friction force between the droplet and the substrate, even though it has a pronounced effect on the size and structure of the wetting ridge, especially above the cloaking transition.

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Section: Results and Discussioncontrasting

confidence: 99%