Human writing and drawing date back at least 30,000 years and include traditional techniques such as carving, etching, and ink printing/writing, as well as newer methods such as electron lithography. Now a team of German physicists have found a unique method for writing on water and other liquid surfaces, according to a recently published paper in the journal Small.
How is it possible to write on water?
According to the authors, most classical writing methods involve the same basic approach, such as carving a line or laying down ink. On a solid substrate, strong intermolecular forces help inscribed shapes maintain their shape, but this is not the case for surfaces immersed in liquids. That’s why scientists have developed a unique method for this type of surface.
Mechanism of writing in water: As the ‘pen’ draws in ink, unnecessary ink is left behind to mark the path.
The solution, according to co-author Thomas Palberg of Johannes Gutenberg Universitaet Mainz, is to put the ink directly into water and use a microbead made of ion exchange material as a pen, ranging from 20 to 50 microns in diameter. In this way, the bead remains so small compared to the “ink” chamber that it does not create any vortex.
The bead “writes” by changing the local pH of the water, attracting ink particles to these areas. It is possible to “write” a letter in water by moving the bead in a trajectory that follows the letter or character it is trying to draw. The ink particles then accumulate along this trajectory, and as a result, you write whatever you want on the water.
Palberg emphasizes that this study is primarily a proof of principle and that their research is still very preliminary. But the team thinks their method should be able to reproduce any type of writing that uses continuous lines. It may even be possible to make cuts between individual letters by turning the ion exchange process on and off when necessary, or by deleting and/or correcting what is “written”.
Researchers think using “sticky” inks that are sensitive to UV light could help keep lines and letters in place for longer. “In addition to beads made of ion-exchange resins, ‘pencils’ consisting of particles that can be heated with lasers or even individually steerable microswimmers can be used,” said co-author Benno Liebchen from TU Darmstadt. said.
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