Laser Paintbrush Creates Works of Art on Titanium
(Inside Science) -- Around 73,000 years ago, an unknown artist used a mineral pigment crayon to make a mishmash of red lines on a stone flake, creating the oldest known drawing made by Homo sapiens. Evidence of abstract markings from earlier human species, such as a zigzag pattern on a clamshell by Homo erectus, traces the potential origins of art still further back in time.
While the urge to create visual art is ancient, and materials like paints and charcoal have remained a staple in artists' toolboxes for tens of thousands of years, scientific innovations have given contemporary creators a variety of new materials to work with, from fast-drying, polymer-based acrylic paints to computer graphics for digital art.
Now, scientists have invented a new laser-based tool for artists to paint, erase and change the color of strokes on a metal canvas at will. The laser paintbrush, as they call it, is being developed into a hand-held device that could be used much like a classical brush, but without the need for external pigments or dyes. However, it currently works more like a printer, where the laser beam is scanned over the metal line-by-line to apply individual strokes.
"Maybe we can see in 10 or 15 years that artists will use our tool to create really new types of art that used to be impossible to make," said Yaroslava Andreeva, an engineer at ITMO University in Russia. "We showed our laser-painted works to people from our local museum of modern art, and they were very interested to try the hand-held version for themselves when it is ready."
The laser paintbrush heats the metal surface up to the point that it starts to evaporate, generating a thin film of metal oxide that interacts with light in a way that produces different colors. Andreeva and her colleagues re-created miniature versions of masterpieces such as Vincent van Gogh's "Starry Night" on a titanium alloy in just three minutes. As opposed to pieces made with pigments or dyes, these images are very durable and do not require any special storage environment. A study describing the new tool was published by the journal Optica in April.
"I think that this technique's most valuable contribution to art may be in its long-term stability. Oxide coatings are rugged and long-lasting, and titanium dioxide is a very sturdy molecule," said artist Greg Dunn, who works with etched metals and gold leaf but was not involved in the study. "I would expect that, under normal display conditions, the color on these would last a very long time."
The researchers produced about 30 different colors with laser oxidation, ranging from reds and yellows to blues and purples. The physics behind the effect -- a phenomenon called thin-film interference -- is also what causes the iridescent sheen of an oil film sitting on a puddle of water.
In the case of oil and water, one incoming light wave is reflected off the top surface of the oil film, while another is reflected off the bottom surface. For some colors, the waves essentially cancel each other out and are eliminated from the reflected light. This leaves only certain colors to be observed as a result. How the waves interfere depends on the thickness of the film, as well as other factors such as the optical properties of the oil and water.
With the laser paintbrush, color is produced by the interference between light reflected off the top of the oxide layer and the titanium surface. By toying with the various parameters of the laser, Andreeva and her colleagues could control the exact temperature of the device to evaporate more or less titanium to produce oxide layers of precise, desired thickness.
"Depending on the thickness, we could see different colors. So usually if you have thicker films, you can see blue or light blue, and if you have a thinner layer, you can see red or orange," said Andreeva. They also found that another pass of the laser could be used to erase and change colors repeatedly without negatively affecting the final product.
Despite the technology's novelty, Dunn and his colleague Brian Edwards harbor some doubts that the technique will stand out visually next to more traditional metal printing methods. They feel it would catch on better with artists if the laser paintbrush incorporated a unique visual effect into the piece, such as directional reflectivity or color shifting.
"From an artistic perspective, I was hoping to see some sort of novel optical effects that achieve something which goes beyond what I would expect to achieve with a dye on metal," said Edwards, an artist and senior research investigator at the University of Pennsylvania. "While their method of achieving color is very different, I'm not sure my eye would be able to notice."
Others praise the researchers for achieving reversible and alterable coloration. Sebastian Cucerca, a research engineer in the Computation, Appearance and Manufacturing Group of the Max Planck Institute for Informatics, notes that the possibility to selectively shift colors of already laser-marked areas has many benefits. For example, it may lower costs of prototyping and production by reducing material waste.
"Especially in the field of art and design, artists can directly mark their drafts without changing the substrate, which makes the process faster and increases its usability," he said. "Furthermore, erasing marked areas enables exciting possibilities regarding the reusability of materials, making the procedure of laser-marking more environmentally friendly."
Ting Xu, professor of engineering and applied science at Nanjing University in China, mentions that other methods using thin films or nanostructures to create bright, saturated colors have not been able to easily shift from one hue to another.
"Recently, most color research work has run into a stumbling block with respect to engineering 'dynamic' or 'erasable' color presentation," wrote Xu in an email to Inside Science. "In contrast, the current creative laser paintbrush technology overcomes these shortcomings and thus truly paves the way for creating a new kind of modern art and design."