GEORGIA TECH (US) — Scientists have “painted” the world’s most famous painting on a substrate surface approximately 30 microns in width—or one-third the width of a human hair.
The “Mini Lisa” demonstrates a technique that could potentially be used to achieve nanomanufacturing of devices, researchers say, because they were able to vary the surface concentration of molecules on such short-length scales.
The image was created with an atomic force microscope and a process called ThermoChemical NanoLithography (TCNL). Going pixel by pixel, the team positioned a heated cantilever at the substrate surface to create a series of confined nanoscale chemical reactions.
On the left is the “Mona Lisa” with representation of the temperature that needs to be applied at each position on the surface to get the appropriate final result. On the right is the “Mini Lisa.” (Credit: Georgia Tech)
By varying only the heat at each location, researchers controlled the number of new molecules that were created. The greater the heat, the greater the local concentration.
More heat produced the lighter shades of gray, as seen on the Mini Lisa’s forehead and hands. Less heat produced the darker shades in her dress and hair seen when the molecular canvas is visualized using fluorescent dye. Each pixel is spaced by 125 nanometers.
“By tuning the temperature, our team manipulated chemical reactions to yield variations in the molecular concentrations on the nanoscale,” says Jennifer Curtis, associate professor of physics at Georgia Institute of Technology (Georgia Tech) and lead author of the paper published in the journal Langmuir.
“The spatial confinement of these reactions provides the precision required to generate complex chemical images like the Mini Lisa.”
Production of chemical concentration gradients and variations on the sub-micrometer scale are difficult to achieve with other techniques, despite a wide range of applications the process could allow.
The Georgia Tech TCNL research collaboration, which includes associate professor Elisa Riedo and Regents professor Seth Marder, produced chemical gradients of amine groups, but expects that the process could be extended for use with other materials.
“We envision TCNL will be capable of patterning gradients of other physical or chemical properties, such as conductivity of graphene,” Curtis says. “This technique should enable a wide range of previously inaccessible experiments and applications in fields as diverse as nanoelectronics, optoelectronics, and bioengineering.”
Another advantage, is that atomic force microscopes are fairly common and the thermal control is relatively straightforward, making the approach accessible to both academic and industrial laboratories.
To facilitate their vision of nano-manufacturing devices with TCNL, the team has recently integrated nanoarrays of five thermal cantilevers to accelerate the pace of production.
Because the technique provides high spatial resolutions at a speed faster than other existing methods, even with a single cantilever, Curtis is hopeful that TCNL will provide the option of nanoscale printing integrated with the fabrication of large quantities of surfaces or everyday materials whose dimensions are more than one billion times larger than the TCNL features themselves.
Atomic force microscope (AFM) modified with a thermal cantilever. The AFM scanner allows for precise positioning on the nanoscale while the thermal cantilever induces local nanoscale chemical reactions. (Credit: Georgia Tech)
Source: Georgia Tech