Biological and Synthetic Self-Cleaning Surfaces
- PDF / 565,021 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 3 Downloads / 268 Views
Synthetic SelfCleaning Surfaces
Jan Genzer and Abraham Marmur
opposite behavior. For instance, the skin of some fish and reptiles appears to prevent bioadhesion. Insects also benefit from the design of their wings and legs that make them nonwettable. Nonwettability permits water striders (Gerris remigis) to stroll effortlessly on water (Figure 1f), even in the rain. The unique hierarchical structure of their microsetae along with hydrophobicity of their feet (fraction of air = 97%) can support the insect’s weight; a single leg can hold up 152 dyn (1.52 mN), which is 15 times the entire water strider’s body weight.
Water Repellency in Bird Feathers and Plant Leaves Abstract In this contribution, we briefly discuss how various physicochemical properties of surfaces affect the wettability and self-cleaning character of both naturally occurring and synthetic surfaces. Using a few selected examples from nature, we discuss the superhydrophobic effect and antifouling character of such surfaces and how these properties are associated with variations in surface chemical composition and topography. We also review a few special case studies aimed at adopting these biomimetic schemes to design and fabricate functional self-cleaning surfaces.
Introduction After decades of research, it has become clear that the attributes of biological surfaces stem from a complex interplay between chemistry, surface morphology (such as texture), mechanical properties (such as modulus), and polarity1 and that these diverse surface characteristics play a pivotal role in determining the functionality of biological materials. Wettability, the basic principles of which are outlined in the introductory article in this issue, provides a convenient measure of the self-cleaning capability of biological surfaces. Surfaces exhibiting high contact angles (θ), so-called superhydrophobic surfaces, are often capable of self-cleaning. However, the determinants of self-cleaning are far more complex; the aforementioned traits typically act together to produce a self-cleaning surface. In this article, we briefly demonstrate this notion with a few examples.
The Diverse Effects of Surface Texture on Biological Function The unique textures of biological surfaces are responsible for many remarkable feats of nature. For instance, the eyes of moths (Figure 1a) consist of hundreds of hexagonally organized microscopic pillars, each approximately 200 nm in height, that result in a very low reflectance for visible light. This nearly perfect antireflective surface of the eye in essentially any direction allows the eye to function as a sort of biological “black hole.”
742
Another surface texture example involves the colorful wings of butterflies (Figures 1b–d). The wing scales are hierarchically organized at various length scales.2 Whereas red and yellow wing colors typically originate from colored pigments, blue and green shades result primarily from light scattered off the complex scales of the wing. The sizes and spatial arrangement of the scales and their ribs par
Data Loading...
