Scientists make world's smallest Mona Lisa

The world’s most famous smile is now the world’s smallest.

Researchers at the Georgia Institute of Technology have “painted” the smallest version of the Mona Lisa ever -- approximately 30 microns in width, or just a third as wide as a human hair.

The micro-method relied not on paintbrushes or pencils but chemistry, and a new process called ThermoChemical NanoLithography (TCNL), in which incredibly precise variations in heat produced lighter or darker shades of gray in a special dye.

"By tuning the temperature, our team manipulated chemical reactions to yield variations in the molecular concentrations on the nanoscale," said Jennifer Curtis, an associate professor in the School of Physics and the study's lead author. "The spatial confinement of these reactions provides the precision required to generate complex chemical images like the Mini Lisa."

Each pixel in the photograph is spaced by 125 nanometers.

The process was difficult to achieve and didn’t yield hard edges to regions, giving the painting a blurry, soft-focus effect. But the researchers expect to be able to expand the process to other materials that may yield a better effect.

"This technique should enable a wide range of previously inaccessible experiments and applications in fields as diverse as nanoelectronics, optoelectronics and bioengineering," Curtis said.

A paper on the process, called “Fabricating Nanoscale Chemical Gradients with ThermoChemical NanoLithography,” was published online by the journal Langmuir.