Scientists draw on liquid with laser light

Laser light has been used for drawing on a solid surface, such as a TV screen or an LCD monitor, but now scientists have for the first time managed to draw on a liquid solution.
The discovery, by researchers from the Laboratory of Polymer Chemistry in the University of Helsinki, is particularly significant for the development of new materials for optics and electronics.
The researchers have manufactured photochemically active polymers which can be dissolved in water or certain alcohols. The new soluble, photosensitive polymer has been created by doctoral student Szymon Wiktorowicz.
In the study, a 365-nm laser was aimed at a solution into which the polymer was partially dissolved. When exposed to light, the polymer switched its conformation, dissolving completely and leaving a clear form which was visible in the cloudy solution.

The polymer chain created by Wiktorowicz includes azo compounds which can be switched from a trans conformation to a cis conformation using light.
As the two conformations are different in solubility, a ray of light can "draw" in an ethanol-based dispersion of the polymer. The switch from trans to cis happens in the entire polymer chain.
This effect where light causes the polymer to dissolve completely and be made visible can last several hours depending, for example, on the concentration of the solution, researchers said.
The research was published in Macromolecules journal.