For 1st time, scientists write words in liquid water

One-line drawing of a complex pattern with rectangular and 45° angles as well as multiple line crossings. The inset shows the intended result (Das Haus vom Nikolaus).
One-line drawing of a complex pattern with rectangular and 45° angles as well as multiple line crossings. The inset shows the intended result. (Image credit: Lukas Hecht)

Scientists have discovered a way to write directly into liquid water, creating clear and long-lasting patterns which float below the surface of the fluid.

In the new study, published Aug. 21 in the journal Nano Micro Small, Benno Liebchen and colleagues at the Technical University of Darmstadt and Johnannes Gutenberg University in Germany have developed a method to create long-lasting writing inside of a liquid. The water-writing  relies on a chemical process called diffusioosmosis — a spontaneous movement of different types of particles, caused by a difference in concentration within a liquid mixture.

The team's liquid mixture, which contains a low concentration of charged particles called ions, acts as the "paper."  The "ink" is made up of large colloidal (solid) particles, which are dispersed thinly through the entire solution. The "pen" is a single small ion-exchange bead — a particle which is able to swap the charged particles in the liquid mixture for different, smaller charged particles.

"When you exchange larger ions with smaller ions, the smaller ions can move (diffuse) faster and that leads to a difference in concentration," Liebchen told Live Science. "This concentration gradient in the ion distribution forces the liquid at the bottom of the container near where the bead is to move. The moving liquid carries the visible colloidal particles (the 'ink') along with it."

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By rotating the liquid (paper) on a small stage, Liebchen and Palberg exploited gravity to direct the ion-exchange bead pen through the solution to create different patterns. As the bead moves through the liquid, the colloidal particles are drawn into its wake by this concentration gradient effect, resulting in a visible line where the pen has been.

"Importantly, because the pen is small, it doesn't disturb the surrounding solvent too much — a larger pen would agitate the water and destroy what you were writing," Liebchen said. "The colloidal particles are too big and heavy to move much in still water within the time scales of the experiment which is why the lines remain visible."

The team developed this technique using water as the paper and silica particles as the ink so they next explored whether other paper, pen, and ink combinations worked.

"Many aspects of the writing approach are quite robust with respect to changing those components, but there are limits of course," said Liebchen. "For example, if the ink particles are too small, you wouldn't see them very well or they would move too much whereas if they're too big, they wouldn't follow the fluid very well. It's a balance but overall the method is quite general."

The team are now looking at different ways of steering the pen by using magnetism or electrical fields instead of gravity and possibly extending this system into deeper liquid mixtures.

Victoria Atkinson
Live Science Contributor

Victoria Atkinson is a freelance science journalist, specializing in chemistry and its interface with the natural and human-made worlds. Currently based in York (UK), she formerly worked as a science content developer at the University of Oxford, and later as a member of the Chemistry World editorial team. Since becoming a freelancer, Victoria has expanded her focus to explore topics from across the sciences and has also worked with Chemistry Review, Neon Squid Publishing and the Open University, amongst others. She has a DPhil in organic chemistry from the University of Oxford.

  • TSSoules
    As a matter of fact,

    I'll be reading at the Decatur GA Oublic Library on the 19th as the 5th reader in the Written in Water series.
  • sheetal007
    Scientists used a process called 'diffusioosmosis' to write words that lingered in liquid water. Scientists have discovered a way to write directly into liquid water, creating clear and long-lasting patterns which float below the surface of the fluid.

    For more information contact us:-
    Website:- No. 9999196162
  • mahnoor1
    Breaking barriers in communication! Scientists achieve a remarkable feat by writing words in liquid water for the first time. This groundbreaking accomplishment could revolutionize various fields, from data storage to environmental monitoring. Imagine the possibilities for transmitting messages in water-rich environments or even underwater communication networks. This discovery is not just a drop in the ocean; it's a wave of innovation, fit for a king WhatsApp era of connectivity.
  • Hartmann352
    Traditional writing techniques comprise carving and engraving as well as printing and writing with ink. Earliest human drawings date back some 30 000 years, possibly even much longer.1] As a visible language, writing appeared in the Middle East between 3400 and 2600 before the Common Era.2, 3] These techniques continue to coexist as means of storing and transporting information, nowadays accompanied by various multimedia techniques for displaying.4] In addition, various novel techniques extend and complement these traditional techniques, including (electron) lithography, optical tweezing, direct printing, or force microscopic manipulation.5-12] Remarkably, the size of glyphs and letters covers the range from a few hundred meters13] down to the atomic scale14] and even below.15] In the more classical approaches, one creates a local, line-shaped variation of the material density in or on an extended substrate acting as background: A line is carved out or some ink is deposited. A solid substrate stabilizes the density variation by strong intermolecular forces, keeping it in shape. The same principle has been applied to write on surfaces submerged in a fluid. For instance, scanning probe lithography was used to carve or deposit lines within or onto self-assembled monolayers submerged in fluids containing suitable chemicals.16, 17] In addition, sophisticated micron-sized structures have been printed using two-photon polymerization.18, 19] UV-polymerization and crosslinking were also used to write on a solid surface within a liquid starting from a dispersion of reactive chemicals to manufacture patterns with superb thermoresponsive mechanical properties.20] There are now even commercial scuba diver slates available for underwater writing on a substrate. Importantly, however, all these approaches still rely on a substrate i) for fixing the written structures and ii) for providing mechanical support. In contrast, “writing into a fluid” requires a mechanism that does not depend on such localization measures. The mechanism must also be intrinsically robust against rapid line dispersion, which would cause short lifetimes of any drawn lines. In fact, even in a quiescent (convection-free) fluid, the moving pen would transfer kinetic energy to the fluid, provoking line dispersion by locally created eddies. While such local eddies are rather unimportant when the pen is much smaller than the written letters, as, e.g., in skywriting,21] the creation of fine, durable, and freely-floating lines remains challenging. In fact, to write fully reconfigurable lines into a liquid at the microscale, an approach fundamentally different from underwater ink deposition or line carving and a new type of micro-pen are required. To develop such an approach, we exploit the following ideas.

    Incidentally, a mobile fluid offers an alternative way of writing lines by particle transport toward a prescribed pattern. Imagine to start from a homogenous density of ink particles in a quiescent fluid and to use a pen that attracts the ink particles toward itself and/or its trajectory. If the resulting accretion process is sufficiently efficient and fast as compared to the subsequent dispersion of the ink particles, an increase in ink density may result past the pen, and a line is written. As key ingredients, this approach requires a sufficient range of particle-transporting attraction, a slow line dispersion, and a suitable way of pen-steering.

    To meet the first requirement, the directed transport of colloidal particles by chemical, thermal, or light-intensity gradients can be exploited. A key example is phoretic effects, where, in general, the imposed gradient leads to a difference in chemical potential along a particle surface and drives a slip flow of the adjacent fluid along the surface, which, in turn, evokes directed motion of the particle.22-26] Using a large chemical-loaded “beacon” falling under gravity, Banerjee et al. created a colloidal over-density evolving along the trajectory within a few minutes.27] Here, colloidal motion relied on the local strength and direction of the gradient of electrolyte concentration. While these pioneering experiments demonstrate the possibility of writing freely buoyant lines within a fluid, they lack the option of deliberate pen steering.

    In this work, we demonstrate a generic method for writing lines and letterings into a liquid rather than onto a solid. This method uses an ion-exchange resin bead (IEX) as a fully steerable micro-pen and exploits the presence of a solid substrate only for line assembly but not for fixing the ink. Instead, lines are written near a substrate but are not attached to it yielding freely floating long-lived lines which can be reconfigured and allow us to recycle the ink for writing new lines before optionally fixing them to the substrate.20, 28, 29] To achieve this, we exploit an effective way to transport colloids along extended surfaces: The ion-exchange resin bead (pen) evokes a so-called diffusio–osmotic (DO) flow.22, 30, 31] Such a flow emerges because the ion-exchange process induces a nonuniform concentration profile that causes a stress (force) on the solvent within the interfacial layer of the substrate resulting in a solvent flow towards the IEX.32] This flow then advects colloidal tracers towards the IEX, which can be viewed as an effective attraction between the IEX and the tracers.33] In the past, DO flows have been successfully employed with fixed sources,32-38]self-propelling sources,39, 40] and combinations of sources and sinks41] to create centrally symmetric or asymmetric assemblies of tracer particles at the source. Here, we exploit this mechanism to dynamically assemble a line of tracer particles (ink) in the wake of a moving ion-exchange resin bead. Once assembled, those tracers will disperse only very slowly by thermal diffusion in the eddy-free fluid. Moreover, the ongoing pen-induced DO flows focus ink particles toward the center of the written lines supporting their durability and sharpness.

    Our results exemplify a generic pathway for writing and drawing fine, free-floating but durable lines in a liquid medium. Our approach is modular and allows combinations of different inks, drives, steering, and, optionally, fixation techniques. This could be used in the future for structuring liquids with deliberate line-based patterns, decorate, and thus visualize chemical tracers, or create desired initial states for future colloid experiments.

    Any kind of written form that can be produced using continuous lines can be readily reproduced, as other simulations have shown. Moreover, interruptions, such as breaks between separate letters, could also be achieved because, for example, the ion exchange process could be switched on and off at will using light exposure techniques. Even erasure and correction of what has been written is possible.