Handheld 'laser paintbrush' to enable drawing on metallic surfaces

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Laser pulses can be used to heat metals and obtain an ultra-thin film of metal oxides that exhibit light interference effects to generate different colours. (Image: ITMO University)

Scientists from ITMO University in Russia are developing a handheld ‘laser paintbrush’ capable of applying different colours to metallic surfaces.

Lasers are already used in industry to mark metallic surfaces with company logos, barcodes, and trademarks.

Until now however, only robots controlled by a computer algorithm were able to draw on metallic surfaces. The researchers have therefore devised a special device that would allow artists to draw on a sheet of metal with the help of laser colouring. This would remove the need to use paints or toxic substances when applying colourful images to metals.

‘We use laser pulses to heat the material below melting point and thus obtain an ultra-thin film of metal oxides in a laser-irradiated zone,’ explained Yaroslava Andreeva, a co-author of an Optica paper describing the technique. ‘Like any other, this film exhibits interference effects. It reflects certain areas of the spectrum in various ways and as a result, we see different colours. The same effect can be observed in soap bubbles or oil spills in puddles.’

The colour depends on the laser’s scanning speed and the surface’s cooling time. Thus, the faster the metal cools off, the faster an oxide film appears and the thinner it is. Depending on the thickness of such films, the light will act differently and certain parts of the spectrum will interfere at the output. As a result, a certain colour will be observed. The thickness modification leads to colour change – from light yellow to red, purple, dark and light blue. The scientists have shown that the colour palette – which contains over 20 colours and shades – can be expanded due to the variability and accuracy of laser parameters. 

Currently, in order to undo a mistake on a metallic canvas, artists must resort to dangerous chemicals or vacuum or inert gas processing. The laser paintbrush will provide a simple and convenient way to undo such mistakes, according to the researchers.

‘How does it work?’ said Andreeva. ‘Let’s say, an artist used red colour for their painting but then changed their mind and decided to try yellow. To correct this mistake, you need to expose certain areas to the laser beam once again and change its speed rate. Then, the previous layer will be removed and a new colour (e.g. yellow) will appear. If the artist isn’t satisfied with the result, we repeat the procedure and get a blue colour.’

Images on a metal plate created with the use of laser technology. (Credit: ITMO University)

To demonstrate the capabilities of laser colouring, the researchers made reproductions of Van Gogh's paintings The Starry Night and Self-portrait with the help of programmable automated laser systems.

The actual device for laser painting or ‘laser paintbrush’, as the researchers call it, has yet to be created. This will be a handy pen-like device connected to a laser source through a fibre-optic cable. Its design has been developed, however, and now the scientists are working on its prototype, which will be finished by the end of summer.

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