Nano-Surfaces

Nanostructure engineering to create superhydrophobic and superhydrophilic surfaces has been a hot topic. Applications include the design of "self-cleaning, anti-sticking" surfaces, drag reduction, and improvements of tranditional processes such as printing and lubrications [1-3]. In addition, there surfaces are extensively studied as a model system to investigate the interfacial interactions between liquid, solid and air [4] and the dramatic influences of surface topologies on liquid behaviors have been demonstrated [5].

The conventional studies of nanostructured surfaces, however, focus on homogeneous surface features and the nanosturctured surfaces with heterogeneous properties has been of recent interest and drawn more attentions due to the potentials to control the liquid motions [6,7]. Nevertheless, the directional and actively controllable liquid motion have not been achieved yet.

In this work, we develop novel tunable nanostructures to investigate the dynamic behavior of droplets spreading and liquid motions. The nanopillar arrays which are asymmetric and tunable. Some of the pillars have magnetic tips such that upon application of a magnetic field, the deflection angle can be altered. These tunable nanostructured surfaces have great potential to manipulate fluid for applications in microfluidic, biological, and thermal management systems.

  1. X.-M. Li, D. Reinhoudt, M. Crego-Calama. "What do we need for a superhydrophobic surface? A review on the recent progress in the preparation of superhydrophobic surfaces", Chemical Society Reviews, 2007, 36, 1350-1368.
  2. 2.C. W. Extrand, S. I. Moon, P. Hall, and D. Schmidt, "Superwetting of Structured Surfaces" Langmuir, 2007, 23 (17), 8882-8890.
  3. N.-R. Chiou, C. Lu, J. Guan, L. J. Lee, and A. J. Epstein, "Growth and alignment of polyaniline nanofiberes with superhydrophobic, superhydrophlic and other properties", Nature Nanotechnology, 2007, 2, 354-357.
  4. D. Quéré, "Non-sticking drops" Reports on Progress in Physics, 2005, 68, 2495−2532.
  5. L. Courbin, E. Denieul, E. Eressaire, M. Roper, M. Ajdari, and H. A. Stone, "Imbibition by polygonal spreading on microdecorated surfaces", Natural Materials, 6, 2007, 661-664
  6. J. Drelich, J. L. Wilbur, J. D. Miller, and G. M. Whitesides, "Contact Angles for Liquid Drops at a Model Heterogeneous Surface Consisting of Alternating and Parallel Hydrophobic/Hydrophilic Strips" Langmuir , 1996 ,12 (7), 1913-1922.
  7. H. Gau, S. Herminghaus, P. Lenz and R. Lipowsky, "Liquid Morphologies on Structured Surfaces: From Microchannels to Microchip" Science, 1999, 283, 46-49.