Materials Science

Inching up the Wall

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Science  04 Apr 2008:
Vol. 320, Issue 5872, pp. 23
DOI: 10.1126/science.320.5872.23a

The sight of ivy clinging to a wall may evoke serene contemplation, but for the plant, wending up there takes some work. How do the slender stems scale a sheer surface without slipping back down to the ground? More than 100 years ago, Darwin noted a yellow secretion accompanying the climbing process. Zhang et al. have now taken a closer look and observed a multitude of nanoparticles emanating from disks that the ivy stems pressed against silicon or mica substrates as they grew. After pulling away the branches, the authors used atomic force microscopy to characterize the fairly uniform distribution of ∼70-nm-diameter particles. Chemical analysis by extraction into organic solvent and subsequent high-performance liquid chromatography revealed a complex composition, of which the 19 most prominent components were characterized by mass spectrometry. These compounds ranged in molecular weight from ∼300 to ∼700, comprising 18 to 38 carbons together with hydrogen, nitrogen, oxygen, and sulfur. The precise adhesion mechanism remains unclear, but the authors highlight the high surface area of contact fostered by nanoparticle secretion. — JSY

Nano Lett. 8, 10.1021/nl0725704 (2008).

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