Description: The Naval Research Laboratory (NRL) and Pennsylvania State University have developed a nanofilm comprised of structured poly-(p-xylyene) (PPX) with directional wetting, adhesion, and droplet transport properties. The direction and extent of adhesion and wetability is adjusted through the formation of the PPX nanorods, which are fabricated with commercially available vapor deposition equipment. The result is a pattern of columns oriented at a non-perpendicular angle and a nanoscale surface roughness with unidirectional wetting properties. The film allows for water droplets to be pinned to the surface in several directions, including vertically. However, when the film is rotated to the release position, the microscale droplets are transported off the film smoothly and without deformation. The nanofilm’s ability to unidirectionally transport water droplets allows for numerous microfluidic and lab on chip applications. NRL has all rights to this technology.

Advantages/Features Include:

  • Directional transpost of fluid droplets on fluidic channels
  • Adhesion along one direction, release of water along opposite direction
  • Hydrophobic, contact angle equal to or greater than 90 degrees
  • Smooth microscale droplet motion
  • Decreased drag in release direction
  • PPX nanotubes are easily fabricated by a bottom up vapor-phase technique

Applications Include

  • Microfluidic pumpless devices
  • Hydro turbine friction control
  • Antifouling surfaces
  • Biomedical coatings
  • Ice formation control
  • Moisture barriers
  • Anti-friction layers
  • Microelectronics cooling

References:

  • "An Engineered Anisotropic Nanofilm with Unidirectional Wetting Properties," Nature Materials 2010, 12, 1023-1028.
  • "Controlling the Wettability and Adhesion of Nanostructured Poly-(p-xylyene) Films," Langmuir 2007, 23, 11391-11395.

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