Department of Chemistry, College of Staten Island, City University of New York, 2800 Victory Boulevard, Staten Island, New York 10314, United States.
Langmuir. 2011 Aug 16;27(16):9902-9. doi: 10.1021/la201222a. Epub 2011 Jul 18.
The fabrication and properties of superhydrophobic surfaces that exhibit ratchet-like anisotropic slip angle behavior is described. The surface is composed of arrays of poly(dimethylsiloxane) (PDMS) posts fabricated by a type of 3D printing. By controlling the dispense parameters, regular arrays of asymmetric posts were deposited such that the slope of the posts was varied from 0 to 50 relative to the surface normal. Advancing and receding contact angles as well as slip angles were measured as a function of the post slope and droplet volume. Ratchetlike slip angle anisotropy was observed on surfaces composed of sloped features. The maximum slip angle difference (for a 180° tilt angle variation) was 32° for 20 μL droplets on surfaces with posts fabricated with a slope of 50°. This slip angle anisotropy is attributed to an increase in the triple contact line (TCL) length as the droplet is tilted in a direction against the post slope whereas the TCL decreases continuously when the drop travels in a direction parallel to the post slope. The increasing length of the TCL creates an increased energy barrier that accounts for the higher slip angles in this direction.
描述了具有棘轮式各向异性滑移角行为的超疏水表面的制造和特性。该表面由通过一种 3D 打印技术制造的聚二甲基硅氧烷 (PDMS) 柱阵列组成。通过控制分配参数，可以沉积规则的不对称柱阵列，使得柱的斜率相对于表面法线从 0 变化到 50。作为柱斜率和液滴体积的函数，测量了前进和后退接触角以及滑移角。在由倾斜特征组成的表面上观察到了类似棘轮的滑移角各向异性。对于在斜率为 50°的柱上制造的表面，对于 20 μL 液滴，最大滑移角差（对于 180°倾斜角度变化）为 32°。这种滑移角各向异性归因于当液滴在与柱斜率相反的方向倾斜时，三相接触线 (TCL) 的长度增加，而当液滴沿平行于柱斜率的方向移动时，TCL 连续减小。TCL 长度的增加会产生更高的滑移角，这就是产生更高能量势垒的原因。
