'Pen' can write in water

An international team of scientists has developed a 50-micrometer particle pen made of a special material with the ability to exchange ions in liquid.

Some examples of domestic writing. Photo: Small — Some examples of domestic writing. Photo: *Small*

Water is not a preferred medium for writing because it constantly shifts and swirls, causing the ink to quickly diffuse and lose its shape. However, a team of researchers from Johannes Gutenberg University Mainz (JGU) and Technical University Darmstadt in Germany, and Huazhong University of Science and Technology in China, have developed a special “pen” that can enable writing in this environment. The new research is published in the journal Small.

The new device is a tiny bead, just 50 micrometers wide, made of a special material that exchanges ions in a liquid, creating zones of relatively low pH. Traces of the bead suspended in water are then drawn into an acidic solution, from which continuous lines can be created.

To keep the writing stable, the pen moves water around the beads, rather than moving the beads through the water. Initially, this was done manually, but the team later used a pre-programmed device.

"In water no larger than a 1 euro coin, we have created a simple house-like pattern the size of the dot of the letter 'i' in 18-point font, which we can then observe under a microscope. But we are still at the early stages," said physicist Thomas Palberg from JGU.

The pen's tiny size, and the fact that water flows around it rather than the other way around, ensures that the liquid remains as stable as possible. The lines remain visible for over 15 minutes and can be created in a variety of different shapes using light techniques to activate or deactivate ion exchange.

'Pen' can write in water — Simulates how to draw a straight line. Video : *Small*

In addition to the physical experiments, the team also studied a number of theoretical models to find out the basic mechanisms. They believe that this technique can be extended to other types of pens, for example, a laser-heated pen that can operate independently in water.

“This could even allow parallel writing of structures in water. This would allow the new mechanism to create complex patterns in liquids,” says physicist Benno Liebchen from TU Darmstadt.

While still in its early stages, the new pen has a lot of potential, from creating new forms of art to being able to track chemical traces as it moves through liquid. The team says the new method opens up a versatile way to write, draw, and pattern in liquid.

Thu Thao (According to Science Alert )

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