An engineered anisotropic nanofilm with unidirectional wetting properties

Nat Mater. 2010 Dec;9(12):1023-8. doi: 10.1038/nmat2864. Epub 2010 Oct 10.


Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80 μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film's anisotropic wetting behaviour as a function of measurable film morphology parameters.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Anisotropy
  • Biomimetics
  • Butterflies / physiology
  • Engineering / methods*
  • Hydrophobic and Hydrophilic Interactions
  • Microscopy, Electron, Scanning
  • Models, Biological
  • Nanostructures / chemistry*
  • Nanotubes / chemistry
  • Particle Size
  • Polymers / chemistry
  • Porosity
  • Surface Properties
  • Temperature
  • Video Recording
  • Water / chemistry
  • Wettability
  • Wings, Animal / physiology
  • Xylenes / chemistry


  • Polymers
  • Xylenes
  • poly(p-xylylene)
  • Water