AVS 51st International Symposium
    Surface Science Friday Sessions
       Session SS1-FrM

Paper SS1-FrM8
Measurements of Interfacial Water Properties as a Function of Surface Functionalization Using the IFM

Friday, November 19, 2004, 10:40 am, Room 210B

Session: Hydrated Surface Phenomena
Presenter: G.E. Thayer, Sandia National Laboratories
Authors: G.E. Thayer, Sandia National Laboratories
A.K. Boal, Sandia National Laboratories
B.I. Kim, Sandia National Laboratories
J.E. Houston, Sandia National Laboratories
B.C. Bunker, Sandia National Laboratories
Correspondent: Click to Email
Water exhibits dramatically different structures and properties near interfaces, impacting a wide range of activities including the assembly and properties of nano- and bio-materials, microfluidic and sensor systems. In this work, we use the interfacial force microscope (IFM) to study forces generated by hydrophobic/hydrophilic surfaces in contact with water and the resulting properties of the near-surface water region. The IFM measures force-distance curves between a scanning probe tip and substrate surfaces, providing quantitative measurements of adhesion, long-range (electrical double layer) and short-range (Van der Waals and hydration) forces, and fluid properties such as viscosity. Measurements are performed at the water-solid interface as a function of surface and tip functionalization using self-assembled monolayers (SAMs), temperature, speed, and tip size. Our results indicate that in extreme cases a viscous water layer can form which extends greater than 5 nm from the surface is 6 orders of magnitude more viscous than bulk water. This remarkable effect is due to the interaction of surface hydration forces with the hydrogen-bonding network of water. Such forces are capable of controlling phenomena such as protein adsorption, for example we find forces generated by ordered interfacial water are large enough to resist adsorption of the motor protein kinesin.