Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brownian motion under the microscope

11.10.2005


High precision single-particle measurements validate a corrected form of the equation describing Brownian motion



An international group of researchers from the EPFL (Ecole Polytechnique Fédérale de Lausanne), the University of Texas at Austin and the European Molecular Biology Laboratory in Heidelberg, Germany have demonstrated that Brownian motion of a single particle behaves differently than Einstein postulated one century ago.

Their results, to be published online October 11 in Physical Review Letters, provide direct physical evidence that validates a corrected form of the standard theory describing Brownian motion. Their experiment tracked the Brownian fluctuations of a single particle at microsecond time scales and nanometer length scales, marking the first time that single micron-sized particles suspended in fluid have been measured with such high precision.


A hundred years ago, Einstein first quantified Brownian motion, showing that the irregular movement of particles suspended in a fluid was caused by the random thermal agitation of the molecules in the surrounding fluid.

Scientists have subsequently discovered that many fundamental processes in living cells are driven by Brownian motion. And because Brownian particles move randomly throughout their surroundings, they have great potential for use as probes at the nanoscale. Researchers can get detailed information about a particle’s environment by analyzing its Brownian trajectory.

"It is hard to overemphasize the importance of thoroughly understanding Brownian motion as we continue to delve ever deeper into the world of the infinitesimally small, " comments EPFL’s lead researcher Sylvia Jeney.

Researchers have known for some time that when a particle is much larger than the surrounding fluid molecules, it will not experience the completely random motion that Einstein predicted. As the particle gains momentum from colliding with surrounding particles, it will displace fluid in its immediate vicinity. This will alter the flow field, which will then act back on the particle due to fluid inertia. At this time scale the particle’s own inertia will also come into play. But no direct experimental evidence at the single particle level was available to support and quantify these effects.

Using a technique called Photonic Force Microscopy, the research team has been able to provide this evidence. They constructed an optical trap for a single micron-sized particle and recorded its Brownian fluctuations at the microsecond time scale. "The new microscope allows us to measure the particle’s position with extreme precision," notes University of Texas professor Ernst-Ludwig Florin, a member of the research group.

At this high resolution, they found that the time it takes for the particle to make the transition from ballistic motion to diffusive motion was longer than the classical theory predicted.

"This work ratchets our understanding of the phenomenon up a step, providing essential physical evidence for dynamical effects occurring at short time scales," says Jeney.

Their results validate the corrected form of the equation describing Brownian motion, and underline the fact that deviations from the standard theory become increasingly important at very small time scales.

As researchers develop sophisticated, high resolution experimentation techniques for probing the nanoworld, these dynamical details of Brownian motion will be increasingly important.

Dr. Jeney was awarded the SSOM prize at the August 2005 meeting of the Swiss Society for Optics and Microscopy for her work in photonic force microscopy, the technique used in this research.

Mary Parlange | EurekAlert!
Further information:
http://www.epfl.ch

More articles from Physics and Astronomy:

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

nachricht New functional principle to generate the „third harmonic“
16.02.2017 | Laser Zentrum Hannover e.V.

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>