The theory about particle transport through ionic channels and nanopores needs to be rewritten. NIM scientist Prof Peter Hänggi and his team prove their breakthrough research with simulations and experiments on particle diffusion in channel models.
The phenomenon of diffusion is omnipresent and crucial basis of many every-day processes. Diffusion plays a central role for the transport of very small particles. The investigation of Brownian motions by Einstein, Sutherland and Smoluchowski was the foundation of all further research on diffusion processes, also for Prof Peter Hänggi from the University of Augsburg.
Passing the channel
Scientists from various fields such as physics, chemistry and biology are especially interested in the transport through natural and artificial ionic channels and nanopores. Unavoidable component of all channel structures are confining boundaries. The surface of such boundaries are typically not smooth but exhibit rather complex shapes.
Those structural features affect the spontaneous particle zig-zag movements, jittery Brownian motions, on a molecular level. On one hand, there are direct microparticle interactions with the environment, boundaries and surrounding fluid, of attracting and repelling nature altering the transport velocity. On the other hand, the available phase space for motions along the transport direction is limited and determines it, and therefore induces entropic effects.
Hydrodynamic effects were notoriously difficult, if not impossible to explore quantitatively, as the ubiquitous attracting and repelling interactions of corrugated surfaces are hard to model. Solely entropic effects were involved in analytical calculations although they did not mirror the system in its entirety.
Time- and place-dependency of predictions
For the first time, Prof Hänggi and his research group were able to analyze and quantify hydrodynamic effects from theoretical models and experimental set-ups. Their results strongly suggest a reformulation of the existing theories on channel models. In their study, they measured the mean diffusion time and its variances of spherical particles immersed in water inside corrugated channels.
There are three main results representing new milestones for future research on small-scale motion analysis. They could validate the entropic theory in channels that are much wider than the particles radius, and disprove previous simulations of narrow channels. There, hydrodynamic effects can substantially influence the transport velocity of particles.
The mean diffusion time could be 40 % higher than the prediction of the entropic theory tells. Surprisingly, in those narrow channels, the validity of the entropic theory is restored upon using an experimentally determined, spatially dependent effective diffusion coefficient instead of the Stokes-Einstein diffusion coefficient to include the complexity of the hydrodynamic interactions with corrugated confinement.
Hydrodynamic and entropic effects on colloidal diffusion in corrugated channels.
Yang X, Liu C, Li Y, Marchesoni F, Hänggi P, Zhang HP.
PNAS 2017 Sep 5;114(36):9564-9569. DOI: 10.1073/pnas.1707815114
(Web-Link of the publication: http://www.pnas.org/content/114/36/9564.abstract)
Prof. Dr. Dr. h. c. mult. Peter Hänggi
University of Augsburg
Fon: +49 (0)821-598-3250
Klaus P. Prem | idw - Informationsdienst Wissenschaft
ADP-ribosylation on the right track
26.04.2018 | Max-Planck-Institut für Biologie des Alterns
Flavins keep a handy helper in their pocket
25.04.2018 | University of Freiburg
Magnetic resonance imaging, or MRI, is a widely used medical tool for taking pictures of the insides of our body. One way to make MRI scans easier to read is...
At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.
Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
26.04.2018 | Medical Engineering
26.04.2018 | Power and Electrical Engineering
26.04.2018 | Information Technology