Làm cách nào để viết được dưới nước?

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Human writing and drawing dates back at least 30,000 years and incorporates (kết hợp) traditional techniques (kỹ thuật truyền thống) such as carving (chạm khắc), engraving (khắc họa), and printing/writing with ink, as well as more novel methods such as electron lithography (thuật in thạch bản). Now a team of German physicists has figured out a unique method for writing in water and other fluid substrates (nền chất lỏng), according to a recent paper published in the journal Small.

According to the authors, most classical writing methods involve the same basic approach, in which a line is carved out or ink deposited. On a solid substrate, strong intermolecular forces help the written figures hold their shape, but that's not the case for surfaces submerged (chìm) in fluids. Prior research has used scanning probe lithography to "write' on self-assembled monolayers submerged in fluids, or to bring structures at the micron scale using two-photon polymerization. "There are now even commercial scuba diver slates available for underwater writing on a substrate," they wrote.

...The solution: put the ink directly in the water, according to co-author Thomas Palberg of Johannes Gutenberg Universitaet Mainz, and use a microbead made of ion-exchange material as a pen, measuring between 20 to 50 microns in diameter (đường kính). The bead (hạt) is so small relative to the reservoir of "ink" that it doesn't generate vortices at all. The bead "writes" by altering the local pH value of the water, attracting ink particles (mảnh nhỏ) to those areas. It's possible to "write" a letter in water by tilting the water bath so the bead moves in a trajectory (đường đạn) that traces out whatever letter or character one is trying to draw. Ink particles then accumulate along that trajectory and voila! You have written a letter in water.