To obtain effective surface morphology to control surface wettability, this work investigated the influence of protuberant and concave morphology, which are respectively represented by circle-dimpled and micro-square-...To obtain effective surface morphology to control surface wettability, this work investigated the influence of protuberant and concave morphology, which are respectively represented by circle-dimpled and micro-square-convex morphology, on surface wettability. The geometric morphologies were processed on silicon carbide （SIC） surfaces by a laser-marking machine, and surface wettability was monitored by the measurement of contact angles using the sessile drop method. Correlation analysis between contact angles and morphology parameters was conducted to determine the extent of influence. The results showed that the circle-dimpled diameter had a signific^mt influence on surface wettability, whereas grooved width did not. Additionally the depth of dimples and grooves exerted less influence on controlling wetting behaviors. In addition, surface wettability transformed from a superhydrophilic state to a hydrophobic state on micro-square-convex surfaces; contact angles on cir- cle-dimpled surfaces showed a relatively slow transformation, though the surface wettability also underwent the state change.展开更多
The dynamic wetting characteristics of water droplets on silicon wafers with microscale regular pillars structures and fresh lotus leaves are investigated experimentally.We measured the static contact angle,contact an...The dynamic wetting characteristics of water droplets on silicon wafers with microscale regular pillars structures and fresh lotus leaves are investigated experimentally.We measured the static contact angle,contact angle hysteresis,and roll-off angle of water droplets on both of these superhydrophobic surfaces with a high speed contact angle meter.The dynamic contact angles and internal velocity distribution of water droplets on superhydrophobic surfaces were studied with a high-speed camera system and a particle image velocimetry (PIV) system,respectively.We found that the acceleration of water droplets when they slide off lotus leaves is greater than that of water droplets sliding off the silicon wafers with microscale pillar structures although the static contact angles of water droplets on lotus leaves are slightly smaller than those on the silicon wafers.The reason is that water droplets sliding off lotus leaves have smaller contact angle hysteresis and larger slip velocities.These results indicate that the dynamic contact angle hysteresis and sliding acceleration of liquid droplets are more suitable for reflecting the hydrophobicity of material surfaces compared with static contact angles.Our experiments also show that lotus leaves with multiscale micro/nanostructures have stronger hydrophobicity and self-cleaning properties compared with the micro-structured superhydrophobic surfaces.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51275473)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR14E050001)the Tribology Science Fund of State Key Laboratory of Tribology of China(Grant No.SKLTKF14B13)
文摘To obtain effective surface morphology to control surface wettability, this work investigated the influence of protuberant and concave morphology, which are respectively represented by circle-dimpled and micro-square-convex morphology, on surface wettability. The geometric morphologies were processed on silicon carbide （SIC） surfaces by a laser-marking machine, and surface wettability was monitored by the measurement of contact angles using the sessile drop method. Correlation analysis between contact angles and morphology parameters was conducted to determine the extent of influence. The results showed that the circle-dimpled diameter had a signific^mt influence on surface wettability, whereas grooved width did not. Additionally the depth of dimples and grooves exerted less influence on controlling wetting behaviors. In addition, surface wettability transformed from a superhydrophilic state to a hydrophobic state on micro-square-convex surfaces; contact angles on cir- cle-dimpled surfaces showed a relatively slow transformation, though the surface wettability also underwent the state change.
基金supported by the National Natural Science Foundation of China(Grant Nos. 11072126 and 10872106)
文摘The dynamic wetting characteristics of water droplets on silicon wafers with microscale regular pillars structures and fresh lotus leaves are investigated experimentally.We measured the static contact angle,contact angle hysteresis,and roll-off angle of water droplets on both of these superhydrophobic surfaces with a high speed contact angle meter.The dynamic contact angles and internal velocity distribution of water droplets on superhydrophobic surfaces were studied with a high-speed camera system and a particle image velocimetry (PIV) system,respectively.We found that the acceleration of water droplets when they slide off lotus leaves is greater than that of water droplets sliding off the silicon wafers with microscale pillar structures although the static contact angles of water droplets on lotus leaves are slightly smaller than those on the silicon wafers.The reason is that water droplets sliding off lotus leaves have smaller contact angle hysteresis and larger slip velocities.These results indicate that the dynamic contact angle hysteresis and sliding acceleration of liquid droplets are more suitable for reflecting the hydrophobicity of material surfaces compared with static contact angles.Our experiments also show that lotus leaves with multiscale micro/nanostructures have stronger hydrophobicity and self-cleaning properties compared with the micro-structured superhydrophobic surfaces.
