Scientists go with the flow of liquid particles
A team of Austrian researchers has made an intriguing discovery about how particles in liquids can form in an organised fashion. Writing in the journal Physical Review Letters, the scientists, from Vienna University of Technology (TU Vienna) and the University of Vienna, found that a liquid does not necessarily need to be made up of a disordered bunch of particles. Their research uncovered mysterious structures formed by tiny particles floating in liquids. It seems that under mechanical strain, particle clusters in liquids can spontaneously form strings and dramatically change the properties of the liquid. The researchers analysed computer simulations of the liquids blood, ink and gruel, which all contain tiny suspended particles, or 'colloids'. In some of these liquids, the particles form into clusters which in turn form regular structures, much in the same way atoms in a crystal do. By examining these crystal-like substances, the scientists were able to work out that under mechanical strain, the crystalline pattern can change into a different structure or even vanish completely. If small particles are able to accumulate, they can form clusters; within a cluster, the particles may overlap and mingle. And surprisingly, these clusters are not found at random positions; rather, they spontaneously form a regular structure, or 'cluster crystal'. The scientists observed how at first the crystal structure starts to melt and the connections between the clusters are broken. From these molten particle clusters, a new regular order starts to emerge spontaneously, and long, straight strings of particles are formed, neatly aligned in parallel. Arash Nikoubashman, lead author of the study from TU Vienna, explains: 'Increasing the density of particles adds more and more particles to each cluster - but the distance between them stays the same.' While these strings are being created, the liquid gets thinner and its viscosity decreases. This is due to the strings being able to slide relative to one another. If the material is subject to even more strain, the strings break up too, and what can be described as a 'molten unstructured ensemble of particle clusters' remains, with the viscosity of the liquid increasing again. More and more particles are washed away from their original positions and inhibit the flow. This behaviour is the same for all types of cluster crystals. This study builds on previous studies carried out in the field that already showed how these particles could exhibit strange behaviour under certain external conditions. Moving beyond the theory, their findings have implications for a wide range of practical applications - for blood or large biopolymers like DNA, as well as in the construction of vibration dampers and protective clothing. They are important in biotechnology as well as petrochemistry and pharmacology or any practice that uses tailor-made nano materials.For more information, please visit:University of Vienna:http://www.univie.ac.at/en/
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Austria