Water molecules do not simply swirl around in complete disorder; they can form certain preferred structures. This scientific fact is often presented in entirely unscientific ways, for example when people speak of an alleged “memory of water” or of “water clusters” as a possible explanation for homeopathy, among other things.
All of this has been refuted. But even though water is not a magical information storage medium, its ability to form short-lived structures can have important consequences. This has now been shown in a study by TU Wien, in collaboration with the University of Vienna and the University of Oslo, as part of the FWF-funded Cluster of Excellence “MECS”. The team investigated how easily charged particles can be held at a surface – a question that is important in many areas, such as research on batteries, fuel cells, and biological membranes. The new results show that this can only be understood if one takes into account the structures that water forms on nanosecond timescales.
An Ion Rarely Comes Alone
“When positively charged ions in an aqueous solution attach to a negatively charged surface, this initially sounds very simple from a physics point of view,” says Markus Valtiner from the Institute of Applied Physics at TU Wien. “Opposite electric charges attract, so the particle moves towards the surface. But in reality, things are rather more complicated.”
Charged particles do not move through water on their own. They are surrounded by water molecules, and these molecules can arrange themselves in different ways. How pronounced this ordering is depends on the particle: “Lithium ions, for example, are extremely small and can strongly order the water around them. Cesium ions, by contrast, are large, and this effect is much weaker for them,” says Markus Valtiner.
Ordered Water – But Only for Nanoseconds
However, this order should not be imagined like the orderly arrangement of atoms in a crystal. “This order is statistical in nature,” explains Markus Valtiner. “The water molecules are constantly vibrating, moving very quickly, continuously redistributing themselves, forming weak bonds and breaking them again.”
This means that water molecules are not “information storage media”, as is sometimes falsely claimed. Rather, they perform a kind of “dance” around the ion, and this dance follows certain rules. The dance of water around a lithium ion or a calcium ion is, statistically speaking, in a certain sense more ordered than the dance of water around a cesium ion.
When the ions move towards the surface, they carry this dancing water shell with them. When the ion then attaches to the surface, the surrounding water is forced to structure itself differently than it otherwise would.
“Ions that have a stronger influence on the surrounding water molecules create more order in the water – in thermodynamic terms, this means that they create a state of lower entropy,” explains Markus Valtiner. “And the lower the entropy, the less likely it is for such a state to arise spontaneously. Such ions therefore attach less readily directly to the surface.”
No Esoteric “Memory of Water”
The research team combined high-resolution atomic force microscopy, molecular dynamics simulations, and spectroscopic measurements to measure these surface effects. This led to a thermodynamic model that can now quantitatively describe the adsorption of particles: for the first time, the different effects are considered together – electrostatic attraction on the one hand, but also entropy, the probability of ordering, and interactions with surrounding water molecules.
This now makes it possible to predict more precisely which ions will adhere to a surface and how they will behave there, for example in batteries, electrodes, catalysts, or biological membranes. It is not only electric charges that must be taken into account, but also the statistical order of water.
“This is not a magical memory of water; it has nothing to do with esoteric ideas about water information,” emphasizes Markus Valtiner. “It is simply a highly interesting physical dynamic behavior between different ions and the surrounding water molecules – and we have found a quantitative model that allows us to describe this interaction precisely.”
Science Advances
Experimental study
Not applicable
Entropic-dielectric interplay governs ion adsorption in inner electric double layers
15-May-2026