A smart material that can be switched back and forth between glassy and rubbery could be used to assemble tiny structures placed on its surface.
Researchers at Iowa State University in Ames, led by principal investigators Vladimir Tsukruk and Eugene Zubarev, have shown that the material can be switched back and forth on a scale of just a few molecules.
They say that it could be used for directed assembly of inorganic nanoparticles and nanotubes, as well as to precisely control liquids flowing through microfluidic devices that hold promise for biomedical research and medical diagnostics.
The material comprises a layer of Y-shaped molecules that are attached at the base of the Y.
One of the upright arms is a polymer that is hydrophilic-attracted to water-while the other arm is a polymer that is hydrophobic-repelled by water.
When exposed to water, the molecules collapse into mounds about eight nanometers wide with the hydrophilic arms shielding the hydrophobic arms.
When exposed to an organic solvent such as toluene, the molecules flip so that the hydrophobic arms are on top.
The properties of the two states, such as their stickiness, are dramatically different.
While the arms currently collapse in a random scatter, the researchers are aiming to create ordered patterns that will allow them to make novel surfaces with controllable properties.