DISPLAYS MADE FROM AIR AND WATER
An International team of researchers led by Aalto University has come with an entirely new concept of writing and displaying informations on the surfaces using simply water .
They have exploited a unique way a trapped layer of air behaves on a lotus-inspired, dual-structured, water- repelling surface immersed under water.
To achieve the extreme water-repellence of the lotus leaf, a surface needs to be superhydrophobic. It must have microscopic surface structures that prevent water from wetting the surface completely, leaving a thin layer of air between water and the surface. When such a surface immersed in water, a trapped air layer covers the entire surface.
The researchers have fabricated the structures with two size scales : microposts that have a size of ten micrometers and have tiny nanofilms that are grown on he posts. On such a two level surface the air layer can exist in two different shapes( wetting shapes) that can correspond to the two size scales. They have found that one can easily switch between the two states locally using a nozzle to create a over or under pressure in the water in order to change the air layer to another state.
The minimal energy to switch between two states means the system is bistable, which is essential property of memory devices. Combined with optical effect the system acts as as bistable reflective nature.