The history of human writing and painting can be traced back to at least 30,000 years ago, but "writing in liquid" has always been a problem. An international team led by German physicists has found a unique way to write in water and other liquid matrices, according to a new paper published in Small, the flagship journal in the field of nanomaterials.
As we all know, water is not a writing medium. This is because the ink is constantly moving and swirling, and it quickly spreads out in the water and cannot form structure. Previous research has used scanning probe lithography to "write" on self-assembled monolayers submerged in liquid; now there are also commercial slates that divers can write on underwater. However, all these methods are still substrate dependent.
This time, the research team wanted to design a way to truly "write in liquid". Such a method must prevent the drawn lines from spreading rapidly, and the writer needs a very small "pen" that does not stir up too much turbulence as it moves through the liquid medium. Because in a liquid, the smaller the moving object, the fewer vortices or eddies created.
The team's solution is to put the ink directly into the water and use microbeads made of ion-exchange resin materials as pens, with a diameter between 20 and 50 microns, without generating vortices at all.
The beads "write" by changing the local pH of water, attracting ink particles to those areas. When the water tank is tilted, the ink particles in the beads move along a trajectory that traces the desired letter or character, so it is possible to "write" a letter in water.
In a tank the size of a coin, the researchers drew simple house-like patterns that were as big as an "I" in 18-point font and could be viewed under a microscope.
The researchers say that although the technology is still in its infancy, it opens up a range of possibilities. For example, the technology could potentially be expanded to other types of pens, such as laser-heated pens that can travel through water on their own. This mechanism could also be used to create highly complex density patterns in fluids.
Art has evolved throughout history, and this new approach opens up a "versatile" approach to writing, painting, and fluid composition, even on a microscale.