Water-repelling surface sensor
doi:10.1038/nindia.2011.31 Published online 28 February 2011
Researchers have designed a tiny gallium nitride belt whose surface is dotted with nanosized protrusions. These nanosized cavities repel water, making such a surface potentially useful as a biocompatible sensor.
Nature has a plethora of hydrophobic biosurfaces with special wetting characteristics, one example being the famous lotus leaf. These natural surfaces lure researchers to mimic and fabricate smart devices in biotechnology and nanofluidics.
To achieve the same feat, the researchers passed gallium through ammonia gas at high temperatures to produce a microbelt of gallium nitride whose surface contained nanosized protrusions with nanosized cavities. Each belt had a breadth of 100 μm, a width of 10 μm and a length of ~3–7 mm.
The researchers found that water droplets sat on the surface of the belt at an angle of 150°.
The surface of gallium nitride is generally hydrophilic. This hydrophilic–superhydrophobic switching is thought to result from the presence of special air cavities measuring around 80 nm that are trapped within the surface protrusions.
The surfaces have a high degree of hydrophobicity and may find applications in nanofluidics and for developing biocompatible nanobiosensors, say the researchers.