using hydrophilic/phobic materials

Materials now in labs can turn surfaces hydrophobic or hydrophilic via applied voltages. The first intended use is to shuttle water-based samples around a chip-sized lab with multiple paths and chambers that must be flooded and evacuated under external control.

That's a good idea and garners research money by hitting the hot buttons of health (cheaper organic fluid testing) and terrorism (compact and quick bad-stuff sniffers).

But the real good idea here is when the materials can be made in large quantities and/or in an easily applied coating. Then the hulls of boats can be covered with this material. This may lead to the following advances:

• Silent propulsion with no moving parts.
  Just attract water to the hull at a point (probably an area narrow in the direction of travel, but the full width of the hull), then cause it to become hydrophobic while making the area just behind it hydrophilic. With successive "waves" of this switching, the water will move from the front of the boat to the rear--the definition of propulsion. But no propellor or impellor is required.
• Slipperier boats.
  It is now well-known that certain patterns of turbulence can actually make travel through fluid more efficient. Dimples in golf-balls or scalloped whale fins are common examples. A standing pattern of hydrophilic/phobic areas on a hull may act as golf ball dimples, breaking up the uniform surface and leading to efficiency gains.

by Guy T. Schafer
(First published August 30, 2004)