In an article just published on-line in PNAS, researchers from Wageningen University (Netherlands) report an exception to this rule: when small, micrometer-sized particles are placed on a curved oil-water surface, they arrange in a square pattern, as on a chessboard.
Since a number of decades, scientists are looking for strategies to create ordered crystal structures of regularly arranged small particles. Such crystals are interesting, because they can be used to control, modulate, or steer visible light in applications like lasers or other optical devices. While creating hexagonal patterns is relatively easy – this is the natural way in which the particles tend to order – anything different from that is much more difficult.
The team from the Laboratory of Physical Chemistry and Colloid Science at Wageningen University, part of Wageningen UR, has now found a way to create square particle arrays. To do this, they make use of the surface tension of the underlying oil-water surface, that is the tendency of the surface to minimize its area. When a particle sticks to the liquid surface it deforms the surface somewhat, and thereby increases the total area.
The surface tension acts to minimize these deformations, which can be done by clustering all the particles together. This effect is also responsible for the clumping of breakfast cereals in a bowl of milk or of bubbles at the surface of a soft drink. The researchers have found that this effective attraction between particles resulting from the surface tension depends on how the liquid surface is curved.
A slight curving of the surface already makes the interaction between particles highly dependent on their relative orientation, with attraction in two perpendicular directions and repulsion in the other directions. This is what causes the particles to arrange spontaneously in square patterns.
The researchers believe that their findings will lead to new bottom-up strategies for the design of structured materials, to be used in high-tech optical applications.
Caption: Particle organization on oil-water interface of a droplet. The particles are labeled with a fluorescent marker to make them visible.
Wageningen University is part of Wageningen UR (University & Research centre).The mission of Wageningen UR is ‘To explore the potential of nature to improve the quality of life’. Within Wageningen UR, nine research institutes – both specialised and applied – have joined forces with Wageningen University to help answer the most important questions in the domain of healthy food and living environment. With approximately 30 locations (in the Netherlands, Brazil, Chile, Ethiopia and China), 6,000 members of staff and 9,000 students, Wageningen UR is one of the leading organisations in its domain worldwide. The integral approach to problems and the cooperation between the exact sciences and the technological and social disciplines are at the heart of the Wageningen Approach.
Jac Niessen | Wageningen University
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences