& Fabio Marchesoni talk with ScienceWatch.com
and answer a few questions about this month's Fast Breaking
Paper in the field of Physics. The authors have
also sent along images of their work.
Article Title: Artificial Brownian motors:
Controlling transport on the nanoscale
Authors: Hanggi, P;Marchesoni, F
Journal: REV MOD PHYS
Year: JAN-MAR 2009
* Univ Augsburg, Inst Phys, Univ Str 1, D-86135 Augsburg,
* Univ Augsburg, Inst Phys, D-86135 Augsburg,
* Natl Univ Singapore, Dept Phys, Singapore 117542,
* Natl Univ Singapore, Ctr Computat Sci & Engn,
Singapore 117542, Singapore.
* Univ Camerino, Dipartimento Fis, I-62032 Camerino,
* Korea Inst Adv Study, Sch Phys, Seoul 130722, South
Why do you think your paper is highly
With this comprehensive paper, we survey and discuss the role of symmetry
breaking and its potential for applications for novel transport schemes and
separation methods on the length scales of micrometers right down to the
nanoscale. It's an everyday experience that the elements of symmetry
breaking such as that of left-right symmetry, or forward-backward symmetry,
rule our daily life when we use, for example, a screwdriver or drive a car.
This all becomes a challenge at small length scales, where thermal
fluctuations assume a dominating role. To obtain directed transport, one
must then learn how to overcome the limits imposed by the laws of
equilibrium thermodynamics and take advantage of those nonequilibrium
processes which happen to remain applicable at the molecular scales.
quantum Brownian motor
This objective is by no means a trivial task at the submicron scale, as
mastering these issues would pave the way for the design and engineering of
nanodevices operating in the presence of haphazard Brownian noise, so that
quantum and classical objects can be directed along pre-assigned routes
Does it describe a new discovery, methodology, or
synthesis of knowledge?
The theme of artificial Brownian motors requires a synthesis of different
principles in physics, such as breaking of time-reversal symmetry, the
inclusion of a description of fluctuating variables, and the solution of
balance equations for probabilistic flow of matter and/or information.
Would you summarize the significance of your paper in
Since the turn of the 20th century, Brownian noise has
continuously disclosed a rich variety
of phenomena both in and around physics. The understanding of this
jittering motion of suspended microscopic particles has undoubtedly helped
reinforce and substantiate the pillars of modern physical theories. Its
formal description provided the key to great achievements in statistical
mechanics, the foundations of quantum mechanics, and also astrophysical
phenomena, to name only a few.
Although noise is usually thought of as the enemy of order, in fact it also
plays a constructive role. In our work we show how random Brownian dynamics
and external control forces can be combined so as to enhance detection
and/or in facilitating the directed transmission of information. Prominent
applications range from innovative information processing devices in
physics, chemistry, and physical biology, as well as toward new hardware
for medical rehabilitation.
How did you become involved in this research, and were
there any problems along the way
I have a long standing experience in the field of physics and in developing
methods for systems that are driven far from equilibrium; both classical
and quantum. A prominent case is the phenomenon of stochastic
resonance—i.e., the possibility of boosting the transduction of
information by applying a suitably chosen dose of additional randomness.
This, by now widely appreciated phenomenon, shares some common principles
with the topic of designing machinery fueled by ambient thermal noise and
nonequilibrium perturbations—the theme of Brownian motors—a
notion coined by me in early 1995.
A new generation of micro- and nano-devices for information &
communication technologies (ICT), including sensors, processors and
actuators, will be impossible unless we figure out how to power such
devices. On addressing issues related to nanoscale energy management, such
as noise harvesting, I've been impressed by how Nature has solved the very
same problem at the cell level.
Relatively large stationary fluctuations seem to sustain a surprisingly
efficient molecular network, where mass, charge, and information are being
exchanged inside the cell body. In this work we have further pursued the
notion of "biology inspired nano-devices," regarding the cell molecular
machinery as a blueprint for the engineering of new artificial devices.
Where do you see your research leading in the
The theme of Brownian machinery is very timely these days. It leads to new
possibilities for designing "cars and wheels" on the micro- and nanoscale.
A recent development is the challenge to devise the transport of only a few
cold atoms, which proceeds fully quantum mechanically (i.e., coherently) in
the absence of environmental disturbances. The only "noise" remaining in
fueling directed quantum motion is then the zero-point quantum
Peter Hanggi, Ph.D.
Institute of Physics
University of Augsburg
Augsburg, Germany Web
Fabio Marchesoni, Ph.D.
Department of Physics
University of Camerino