Micro-, nano- and hierarchical structures for superhydrophobicity, self-cleaning and low adhesion

Abstract

Superhydrophobic surfaces exhibit extreme water-repellent properties. These surfaces with high contact angle and low contact angle hysteresis also exhibit a self-cleaning effect and low drag for fluid flow. Certain plant leaves, such as lotus leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical roughness of their leaf surfaces. The self-cleaning phenomenon is widely known as the 'lotus effect'. Superhydrophobic and self-cleaning surfaces can be produced by using roughness combined with hydrophobic coatings. In this paper, the effect of micro-and nanopatterned polymers on hydrophobicity is reviewed. Silicon surfaces patterned with pillars and deposited with a hydrophobic coating were studied to demonstrate how the effects of pitch value, droplet size and impact velocity influence the transition from a composite state to a wetted state. In order to fabricate hierarchical structures, a low-cost and flexible technique that involves replication of microstructures and self-assembly of hydrophobic waxes is described. The influence of micro-, nano-and hierarchical structures on superhydrophobicity is discussed by the investigation of static contact angle, contact angle hysteresis, droplet evaporation and propensity for air pocket formation. In addition, their influence on adhesive force as well as efficiency of selfcleaning is discussed.

Drop Detachment and Motion on Fuel Cell Electrode Materials

“…A large number of papers have focused on superhydrophobic surfaces. [32][33][34][51][52][53][54][55][56]60,61 Those studies have employed microscale patterning with hydrophobic pillars and voids where liquid did not penetrate. They are different from what we report here.…”

Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

“…The self-cleaning action on hydrophobic surfaces is a consequence of their high water contact angles where almost spherical droplets form, which can easily roll away carrying foreign particles off the surface (Blossey 2003;Bhushan and Jung 2011;Liu and Jiang 2011). This form of selfcleaning via rolling droplets is thought to be one of the principle mechanism for removing contaminants from natural and artificial surfaces (Blossey 2003;Bhushan et al 2009;Koch and Barthlott 2009;Bhushan and Jung 2011;Liu and Jiang 2011).…”

“…The kinetic energy from droplet impacts has also been shown to be effective in removing contaminants from superhydrophobic surfaces (Furstner and Barthlott 2005;Bhushan et al 2009). For the droplets to roll away easily, a low hysteresis is required.…”

Analysis of approaches to mathematical description of the characteristics of materials with high hydrophobicity

“…Бушан с сотр. утверждают [75], что переход из со-стояния Каси-Бакстера в состояние Венцеля будет осу-ществляться в том случае, когда максимальная глубина провисания δ капли радиуса R, описываемая уравнением Лапласа (рис. 6), будет больше высоты неровностей по-верхности Н, что может быть выражено неравенством (22).…”

“…Многие авторы [75,[84][85][86] делают вывод, что для достижения устойчивого состояния Касси могут быть использованы поверхности с иерар-хической структурой (рис. 9).…”