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Bio-inspired dewetted surfaces based on SiC/Si interlocked structures for enhanced-underwater stability and regenerative-drag reduction capability.

Lee BJ, Zhang Z, Baek S, Kim S, Kim D, Yong K - Sci Rep (2016)

Bottom Line: Among diverse approaches for drag reduction, superhydrophobic surfaces have been mainly researched due to their high drag reducing efficiency.These structures have an unequaled stability of underwater superhydrophobicity and enhance drag reduction capabilities,with a lifetime of plastron over 18 days and maximum velocity reduction ratio of 56%.Furthermore, through photoelectrochemical water splitting on a hierarchical SiC/Si nanostructure surface, the limited lifetime problem of air pockets was overcome by refilling the escaping gas layer, which also provides continuous drag reduction effects.

View Article: PubMed Central - PubMed

Affiliation: Surface Chemistry Laboratory of Electronic Materials, Department of Chemical Engineering, POSTECH (Pohang University of Science and Technology), Pohang, 790-784 Korea.

ABSTRACT
Drag reduction has become a serious issue in recent years in terms of energy conservation and environmental protection. Among diverse approaches for drag reduction, superhydrophobic surfaces have been mainly researched due to their high drag reducing efficiency. However, due to limited lifetime of plastron (i.e., air pockets) on superhydrophobic surfaces in underwater, the instability of dewetted surfaces has been a sticking point for practical applications. This work presents a breakthrough in improving the underwater stability of superhydrophobic surfaces by optimizing nanoscale surface structures using SiC/Si interlocked structures. These structures have an unequaled stability of underwater superhydrophobicity and enhance drag reduction capabilities,with a lifetime of plastron over 18 days and maximum velocity reduction ratio of 56%. Furthermore, through photoelectrochemical water splitting on a hierarchical SiC/Si nanostructure surface, the limited lifetime problem of air pockets was overcome by refilling the escaping gas layer, which also provides continuous drag reduction effects.

No MeSH data available.


(a) Scheme of a set-up for drag reduction experiment. (b) Snapshots of movements of superhydrophilic and superhydrophobic SiC/Si hierarchical structures for 10 sec in drag reduction experiment, and scheme of a drag reduction mechanism for superhydrophobic surfaces. (c) Velocity variations depending on four different surface structures; flat, superhydrophobic, liquid infused slippery and superhydrophilic surfaces in various gravitational force (Fg). (d) Velocity reduction ratio (ΔV) of three different surface structures; superhydrophobic, liquid infused slippery and superhydrophilic surfaces depending on the velocities of the flat surface.
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f4: (a) Scheme of a set-up for drag reduction experiment. (b) Snapshots of movements of superhydrophilic and superhydrophobic SiC/Si hierarchical structures for 10 sec in drag reduction experiment, and scheme of a drag reduction mechanism for superhydrophobic surfaces. (c) Velocity variations depending on four different surface structures; flat, superhydrophobic, liquid infused slippery and superhydrophilic surfaces in various gravitational force (Fg). (d) Velocity reduction ratio (ΔV) of three different surface structures; superhydrophobic, liquid infused slippery and superhydrophilic surfaces depending on the velocities of the flat surface.

Mentions: To evaluate the drag reduction properties of the superhydrophobic SiC/Si hierarchical structures and their SLIPS samples, a measurement systemfor the sample velocity was designed, as illustrated in Fig. 4a (a detailed explanation isprovided in the method section). By allowing the double-sided superhydrophobic surfaces immersed in water to move along the tilted water filled tank, the velocity of the samples was measured and analyzed for drag reduction measurements. When the sink was tilted by θ°, the gravitational force (Fg) exerted on the sample in the direction of sample’s movement is Fg=mg sin θ, where m is massof the sample, and is the gravitational acceleration. When the substrate starts to move, a drag force caused by the contact between the solid surface and water layer is applied in the opposite direction of the movement. The drag force (FD) is expressed as


Bio-inspired dewetted surfaces based on SiC/Si interlocked structures for enhanced-underwater stability and regenerative-drag reduction capability.

Lee BJ, Zhang Z, Baek S, Kim S, Kim D, Yong K - Sci Rep (2016)

(a) Scheme of a set-up for drag reduction experiment. (b) Snapshots of movements of superhydrophilic and superhydrophobic SiC/Si hierarchical structures for 10 sec in drag reduction experiment, and scheme of a drag reduction mechanism for superhydrophobic surfaces. (c) Velocity variations depending on four different surface structures; flat, superhydrophobic, liquid infused slippery and superhydrophilic surfaces in various gravitational force (Fg). (d) Velocity reduction ratio (ΔV) of three different surface structures; superhydrophobic, liquid infused slippery and superhydrophilic surfaces depending on the velocities of the flat surface.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837397&req=5

f4: (a) Scheme of a set-up for drag reduction experiment. (b) Snapshots of movements of superhydrophilic and superhydrophobic SiC/Si hierarchical structures for 10 sec in drag reduction experiment, and scheme of a drag reduction mechanism for superhydrophobic surfaces. (c) Velocity variations depending on four different surface structures; flat, superhydrophobic, liquid infused slippery and superhydrophilic surfaces in various gravitational force (Fg). (d) Velocity reduction ratio (ΔV) of three different surface structures; superhydrophobic, liquid infused slippery and superhydrophilic surfaces depending on the velocities of the flat surface.
Mentions: To evaluate the drag reduction properties of the superhydrophobic SiC/Si hierarchical structures and their SLIPS samples, a measurement systemfor the sample velocity was designed, as illustrated in Fig. 4a (a detailed explanation isprovided in the method section). By allowing the double-sided superhydrophobic surfaces immersed in water to move along the tilted water filled tank, the velocity of the samples was measured and analyzed for drag reduction measurements. When the sink was tilted by θ°, the gravitational force (Fg) exerted on the sample in the direction of sample’s movement is Fg=mg sin θ, where m is massof the sample, and is the gravitational acceleration. When the substrate starts to move, a drag force caused by the contact between the solid surface and water layer is applied in the opposite direction of the movement. The drag force (FD) is expressed as

Bottom Line: Among diverse approaches for drag reduction, superhydrophobic surfaces have been mainly researched due to their high drag reducing efficiency.These structures have an unequaled stability of underwater superhydrophobicity and enhance drag reduction capabilities,with a lifetime of plastron over 18 days and maximum velocity reduction ratio of 56%.Furthermore, through photoelectrochemical water splitting on a hierarchical SiC/Si nanostructure surface, the limited lifetime problem of air pockets was overcome by refilling the escaping gas layer, which also provides continuous drag reduction effects.

View Article: PubMed Central - PubMed

Affiliation: Surface Chemistry Laboratory of Electronic Materials, Department of Chemical Engineering, POSTECH (Pohang University of Science and Technology), Pohang, 790-784 Korea.

ABSTRACT
Drag reduction has become a serious issue in recent years in terms of energy conservation and environmental protection. Among diverse approaches for drag reduction, superhydrophobic surfaces have been mainly researched due to their high drag reducing efficiency. However, due to limited lifetime of plastron (i.e., air pockets) on superhydrophobic surfaces in underwater, the instability of dewetted surfaces has been a sticking point for practical applications. This work presents a breakthrough in improving the underwater stability of superhydrophobic surfaces by optimizing nanoscale surface structures using SiC/Si interlocked structures. These structures have an unequaled stability of underwater superhydrophobicity and enhance drag reduction capabilities,with a lifetime of plastron over 18 days and maximum velocity reduction ratio of 56%. Furthermore, through photoelectrochemical water splitting on a hierarchical SiC/Si nanostructure surface, the limited lifetime problem of air pockets was overcome by refilling the escaping gas layer, which also provides continuous drag reduction effects.

No MeSH data available.