- Published on 14 June 2022
When a homogeneous mixture is subjected to a thermal gradient, the fluid components are partially separated because of the temperature gradient. This phenomenon, known since the mid-19th century, is called thermodiffusion, the Soret effect or thermophoresis. Despite its relatively small amplitude it impacts many natural systems, such as the salinity gradient in ocean or even pre-biological evolution, and can be exploited in applications ranging from the manipulation of biological macromolecules to isotope enrichment. However, despite numerous attempts by leading researchers, including some Nobel laureates, a full understanding of the microscopic origin of this subtle phenomenon is still lacking and there is no consensus on which model, among the numerous existing ones, is the most reliable to quantify it in dense phases.
- Published on 24 May 2022
The understanding of the clustering and movement of microswimmers has a range of applications from human health to tackling ecological problems.
Microswimmers are biological entities that range from sperm to phytoplankton to bacteria, meaning that their study can have implications for fields in science as diverse as human health and ecology.
A new paper published in EPJ E looks at the dynamics of microswimmers under gravity. It is authored by a team from the Institute for Theoretical Physics at the Berlin Institute of Technology: Felix Rühle, Arne W. Zantop, and Holger Stark.
EPJ E Highlight - The relationship between active areas and boundaries with energy input in snapping shells
- Published on 05 April 2022
New research looks at how the geometry of shells relates to the energy input required to actuate snap-through instability.
In nature, diverse organisms such as the hummingbird and Venus flytrap use rapid snapping motions to capture prey, inspiring engineers to create designs that function using snap-through instability of shell structures. Snapping rapidly releases stored elastic energy and does not require a continuously applied stimulus to maintain an inverted shape in bistable structures.
A new paper published in EPJ E authored by Lucia Stein-Montalvo, Department of Civil and Environmental Engineering, Princeton University, and Douglas P. Holmes, Department of Mechanical Engineering, Boston University, along with co-authors Jeong-Ho Lee, Yi Yang, Melanie Landesberg, and Harold S. Park, examines how restricting the active area of the shell boundary allows for a large reduction in its size, and decreases the energy input required to actuate snap-through behaviour in the shell to guide the design of efficient snapping structures.
- Published on 08 December 2021
The publishers of European Physical Journal E: Soft Matter and Biological Physics are delighted to announce the appointment of Prof Giovanna Fragneto as Editor-in-Chief, starting January 1 2022. Prof Fragneto has served on the Editorial Board of EPJE since 2011, and takes over the EiC role from Prof François Graner, who steps down at the end of this year.
- Published on 29 November 2021
- Published on 16 November 2021
Water, regarded as the matrix of life, is an ubiquitous and peculiar liquid that exhibits a plethora of anomalous properties, both in its stable and metastable bulk states, which fostered a lot of experimental and theoretical studies. Less explored is the field of water and aqueous systems confined in nanoporous materials that, in addition to its fundamental interest, are present in a number of practical situations, including biological and separation processes and energy generation and storage, among others. These facts have triggered a vast amount of research that, so far, has not been conveniently reviewed.
- Published on 12 July 2021
A combination of two simulation techniques has allowed researchers to investigate how swimming microparticles propel themselves through ‘nematic liquid crystals’ – revealing some unusual behaviours
Artificial microswimmers have received much attention in recent years. By mimicking microbes which convert their surrounding energy into swimming motions, these particles could soon be exploited for many important applications. Yet before this can happen, researchers must develop methods to better control the trajectories of individual microswimmers in complex environments. In a new study published in EPJ E, Shubhadeep Mandal at the Indian Institute of Technology Guwahati (India), and Marco Mazza at the Max Planck Institute for Dynamics and Self-Organisation in Göttingen (Germany) and Loughborough University (UK), show how this control could be achieved using exotic materials named ‘nematic liquid crystals’ (LCs) – whose viscosity and elasticity can vary depending on the direction of an applied force.
- Published on 31 March 2021
New experiments reveal the characteristic ways in which self-propelled ‘Janus particles’ with charged coatings will slide across or move away from charged boundaries in their surrounding environments.
By harvesting energy from their surrounding environments, particles named ‘artificial micromotors’ can propel themselves in specific directions when placed in aqueous solutions. In current research, a popular choice of micromotor is the spherical ‘Janus particle’ – featuring two distinct sides with different physical properties. Until now, however, few studies have explored how these particles interact with other objects in their surrounding microenvironments. In an experiment detailed in EPJ E, researchers in Germany and The Netherlands, led by Larysa Baraban at Helmholtz-Zentrum Dresden-Rossendorf, show for the first time how the velocities of Janus particles relate to the physical properties of nearby barriers.
- Published on 17 March 2021
By considering how some bacteria will swim faster within higher nutrient concentrations, researchers have created a more accurate model of how these microbes search for nutrients
Many bacteria swim towards nutrients by rotating the helix-shaped flagella attached to their bodies. As they move, the cells can either ‘run’ in a straight line, or ‘tumble’ by varying the rotational directions of their flagella, causing their paths to randomly change course. Through a process named ‘chemotaxis,’ bacteria can decrease their rate of tumbling at higher concentrations of nutrients, while maintaining their swimming speeds. In more hospitable environments like the gut, this helps them to seek out nutrients more easily. However, in more nutrient-sparse environments, some species of bacteria will also perform ‘chemokinesis’: increasing their swim speeds as nutrient concentrations increase, without changing their tumbling rates. Through new research published in EPJ E, Theresa Jakuszeit and a team at the University of Cambridge led by Ottavio Croze produced a model which accurately accounts for the combined influences of these two motions.
- Published on 19 February 2021
By using a more complex model for neutron scattering data, researchers can better understand the composition of materials such as milk.
Neutron scattering is a technique commonly used in physics and biology to understand the composition of complex multicomponent mixtures and is increasingly being used to study applied materials such as food. A new paper published in EPJ E by Gregory N Smith, Niels Bohr Institute, University of Copenhagen, Denmark, shows an example of neutron scattering in the area of food science. Smith uses neutron scattering to better investigate casein micelles in milk, with the aim of developing an approach for future research.
Smith, also a researcher at the ISIS Neutron and Muon Source in the UK, explains why better modelling of how neutrons are scattered by structures in colloid materials is important. “How well you can understand the structure of a system from scattering data depends on how good your model is, and the better and more realistic your model, the better your understanding,” the researcher says. “This is true for food as for any material. A better understanding of the structure of casein in milk can help better understand dairy products.”