Effects of micro- and nano-structures on the self-cleaning behaviour of lotus leaves

Abstract

When rain falls on lotus leaves water beads up with a high contact angle. The water drops promptly roll off the leaves, collecting dirt along the way. This self-cleaning ability or lotus effect has, in recent years, stimulated much research effort worldwide for a variety of applications ranging from self-cleaning window glasses, paints, and fabrics to low friction surfaces. What are the mechanisms giving rise to the lotus effect? Although chemical composition and surface structure are believed important, a systematic experimental investigation of their effects is still lacking. By altering the surface structure of the leaves while keeping their chemical composition approximately the same, we report in this study the influence of micro- and nano-scale structures on the wetting behaviour of lotus leaves. The findings of this work may help design self-cleaning surfaces and improve our understanding of wetting mechanisms.

Self-cleaning glazing products: A state-of-the-art review and future research pathways

“…Illustration of how self-cleaning glass works, in three steps, from left to right: 1) activation of the coating by UV radiation and natural dirtying, 2) decomposition of the organic dirt, and 3) rain water washes away the loosened and degraded dirt. Source: Pilkington Active [6] Several investigations have been carried out on hydrophilic and hydrophobic surfaces with their respective superhydrophilic and superhydrophobic counterparts or enhancements, and on self-cleaning properties and various possible application areas in general [1,2,5,10,11,12,22,24,25,27,33,34,35,36,37,38,39,40,41,42,43,44,45,46]. It is not within the scope of this work to go into details of all these, as the focus of this work is on self-cleaning characterization methods, state-of-the-art self-cleaning glazing products of today and future research pathways for self-cleaning glazing products of tomorrow.…”

“…The possibilities of the Lotus leaf with its hydrophobicity is investigated in several studies [25,34,35,45], and superhydrophobicity (including ultrahydrophobicity [42]) is furthermore the topic of yet several more studies [11,27,34,36,37,39,40,42,43,44,46], where links to nanostructure of the matter and hence nanotechnology are given in various works [1,12,33,35,40,45]. The large collection of water-repellent and self-cleaning plant surfaces with corresponding contact angles by Neinhuis and Barthlott (1997) [41] should be noted.…”

Wettability and osteoblast cell response modulation through UV laser processing of nylon 6,6

“…This increase in θ arising from the excimer patterned samples can be accounted for by the reduction in apparent polar component, γ P , and apparent total surface free energy, γ T , which is modified by the liquids equilibrium state. That is, the wetting regime had changed on account of the surface topography with the likelihood being that the transition was to a mixed-state wetting regime in which both Wenzel and Cassie-Baxter regimes formed along the liquid-surface interface [25][26][27][28][29][30][31]. It should also be noted here that Table 1 confirms that as a result of the KrF excimer laser-material oxidation of the surface was observed, allowing the surface oxygen content to increase by at most 1.6 %at.…”

Lunar Dust on Heat Rejection System Surfaces: Problems and Prospects

“…One passive system that has been proposed is to apply a texture to the heat rejection surface that is much finer than the typical grain size. This is the same strategy that nature utilizes on the leaves of lotus plants to repel water (Cheng, et al, 2006), and on the feet of geckos to keep terrestrial dust particles from clogging the small structures on their feet that enable them to climb smooth walls. In essence, the dust particles reside on a nanoscale "bed of nails" instead of a smooth surface.…”