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Physicists Turn Liquid into Solid Using an Electric Field

Friday, October 28, 2011

Physicists have predicted that under the influence of sufficiently high electric fields, liquid droplets of certain materials will undergo solidification, forming crystallites at temperature and pressure conditions that correspond to liquid droplets at field-free conditions. This electric-field-induced phase transformation is termed electrocrystallization. The study, performed by scientists at the Georgia Institute of Technology, appears online and is scheduled as a feature and cover article in the 42nd issue of Volume 115 of the Journal of Physical Chemistry C.

“We show that with a strong electric field, you can induce a phase transition without altering the thermodynamic parameters,” said Uzi Landman, Regents’ and Institute Professor in the School of Physics, F.E. Callaway Chair and director of the Center for Computational Materials Science (CCMS) at Georgia Tech.

In these simulations, Landman and Senior Research Scientists David Luedtke and Jianping Gao at the CCMS set out first to explore a phenomenon described by Sir Geoffrey Ingram Taylor in 1964 in the course of his study of the effect of lightning on raindrops, expressed as changes in the shape of liquid drops when passing through an electric field.  While liquid drops under field-free conditions are spherical, they alter their shape in response to an applied electric field to become needle-like liquid drops. Instead of the water droplets used in the almost 50-year-old laboratory experiments of Taylor, the Georgia Tech researchers focused their theoretical study on a 10 nanometer (nm) diameter liquid droplet of formamide, which is a material made of small polar molecules each characterized by a dipole moment that is more than twice as large as that of a water molecule.  

With the use of molecular dynamics simulations developed at the CCMS, which allow scientists to track the evolution of materials systems with ultra-high resolution in space and time, the physicists explored the response of the formamide nano-droplet to an applied electric field of variable strength. Influenced by a field of less than 0.5V/nm, the spherical droplet elongated only slightly. However, when the strength of the field was raised to a critical value close to 0.5 V/nm, the simulated droplet was found to undergo a shape transition resulting in a needle-like liquid droplet with its long axis – oriented along the direction of the applied field – measuring about 12 times larger than the perpendicular (cross-sectional) small axis of the needle-like droplet. The value of the critical field found in the simulations agrees well with the prediction obtained almost half a century ago by Taylor from general macroscopic considerations.

Past the shape transition further increase of the applied electric field yielded a slow, gradual increase of the aspect ratio between the long and short axes of the needle-like droplet, with the formamide molecules exhibiting liquid diffusional motions. 

“Here came the Eureka moment,” said Landman. “When the field strength in the simulations was ramped up even further, reaching a value close to 1.5V/nm, the liquid needle underwent a solidification phase transition, exhibited by freezing of the diffusional motion, and culminating in the formation of a formamide single crystal characterized by a structure that differs from that of the x-ray crystallographic one determined years ago under zero-field conditions. Now, who ordered that?” he added. 

Further analysis has shown that the crystallization transition involved arrangement of the molecules into a particular spatial ordered lattice, which optimizes the interactions between the positive and negative ends of the dipoles of neighboring molecules, resulting in minimization of the free energy of the resulting rigid crystalline needle.  When the electric field applied to the droplet was subsequently decreased, the crystalline needle remelted and at zero-field the liquid droplet reverted to a spherical shape. The field reversal process was found to exhibit a hysteresis.

For the full article, please visit: 

http://www.gatech.edu/newsroom/release.html?nid=71054

Summary: 

Physicists Turn Liquid into Solid Using an Electric Field

Intro: 

Physicists Turn Liquid into Solid Using an Electric Field

Alumni: 

Physicists Turn Liquid into Solid Using an Electric Field

Monday, October 10, 2011

Physicists
have predicted that under the influence of sufficiently high electric fields,
liquid droplets of certain materials will undergo solidification, forming
crystallites at temperature and pressure conditions that correspond to liquid
droplets at field-free conditions. This electric-field-induced phase
transformation is termed electrocrystallization.
The study, performed by scientists at the Georgia Institute of Technology,
appears online and is scheduled as a feature and cover article in the 42nd
issue of Volume 115 of the Journal of Physical Chemistry C.

“We
show that with a strong electric field, you can induce a phase transition
without altering the thermodynamic parameters,” said Uzi Landman, Regents’ and
Institute Professor in the School of Physics, F.E. Callaway Chair and director
of the Center for Computational Materials Science (CCMS) at Georgia Tech.

In
these simulations, Landman and Senior Research Scientists David Luedtke and
Jianping Gao at the CCMS set out first to explore a phenomenon described by Sir
Geoffrey Ingram Taylor in 1964 in the course of his study of the effect of
lightning on raindrops, expressed as changes in the shape of liquid drops when
passing through an electric field.  While liquid drops under field-free
conditions are spherical, they alter their shape in response to an applied
electric field to become needle-like liquid drops. Instead of the water
droplets used in the almost 50-year-old laboratory experiments of Taylor, the
Georgia Tech researchers focused their theoretical study on a 10 nanometer (nm)
diameter liquid droplet of formamide, which is a material made of small polar
molecules each characterized by a dipole moment that is more than twice as
large as that of a water molecule.  

With
the use of molecular dynamics simulations developed at the CCMS, which allow
scientists to track the evolution of materials systems with ultra-high
resolution in space and time, the physicists explored the response of the
formamide nano-droplet to an applied electric field of variable strength.
Influenced by a field of less than 0.5V/nm, the spherical droplet elongated
only slightly. However, when the strength of the field was raised to a critical
value close to 0.5 V/nm, the simulated droplet was found to undergo a shape transition
resulting in a needle-like liquid droplet with its long axis – oriented along
the direction of the applied field – measuring about 12 times larger than the
perpendicular (cross-sectional) small axis of the needle-like droplet. The
value of the critical field found in the simulations agrees well with the
prediction obtained almost half a century ago by Taylor from general macroscopic
considerations.

Past
the shape transition further increase of the applied electric field yielded a
slow, gradual increase of the aspect ratio between the long and short axes of
the needle-like droplet, with the formamide molecules exhibiting liquid
diffusional motions. 

“Here
came the Eureka moment,” said Landman. “When the field strength in the
simulations was ramped up even further, reaching a value close to 1.5V/nm, the
liquid needle underwent a solidification phase transition, exhibited by
freezing of the diffusional motion, and culminating in the formation of a
formamide single crystal characterized by a structure that differs from that of
the x-ray crystallographic one determined years ago under zero-field
conditions. Now, who ordered that?” he added. 

Further
analysis has shown that the crystallization transition involved arrangement of
the molecules into a particular spatial ordered lattice, which optimizes the
interactions between the positive and negative ends of the dipoles of
neighboring molecules, resulting in minimization of the free energy of the
resulting rigid crystalline needle.  When the electric field applied to the
droplet was subsequently decreased, the crystalline needle remelted and at
zero-field the liquid droplet reverted to a spherical shape. The field reversal
process was found to exhibit a hysteresis.

Analysis
of the microscopic structural changes that underlie the response of the droplet
to the applied field revealed that accompanying the shape transition at 0.5
V/nm is a sharp increase in the degree of reorientation of the molecular
electric dipoles, which after the transition lie preferentially along the
direction of the applied electric field and coincide with the long axis of the
needle-­­like liquid droplet. The directional dipole reorientation, which is
essentially complete subsequent to the higher field electrocrystallization
transition, breaks the symmetry and transforms the droplet into a field-induced
ferroelectric state where it possesses a large net electric dipole, in contrast
to its unpolarized state at zero–field conditions. 

Along
with the large-scale atomistic computer simulations, researchers formulated and
evaluated an analytical free-energy model, which describes the balance between
the polarization, interfacial tension and dielectric saturation contributions.
This model was shown to yield results in agreement with the computer simulation
experiments, thus providing a theoretical framework for understanding the
response of dielectric droplets to applied fields.

“This
investigation unveiled fascinating properties of a large group of materials
under the influence of applied fields,” Landman said. “Here the field-induced
shape and crystallization transitions occurred because formamide, like water
and many other materials, is characterized by a relatively large electric
dipole moment. The study demonstrated the ability to employ external fields to
direct and control the shape, the aggregation phase (that is, solid or liquid)
and the properties of certain materials.” 

Along
with the fundamental interest in understanding the microscopic origins of
materials behavior, this may lead to development of applications of
field-induced materials control in diverse areas, ranging from targeted drug delivery,
nanoencapsulation, printing of nanostructures and surface patterning, to
aerosol science, electrospray propulsion and environmental science.

This research was supported by a grant from the U.S. Air Force Office of Scientific Research.

Media Contact: 

Jason Maderer, Media Relations
404-385-2966

Summary: 

Physicists
have predicted that under the influence of sufficiently high electric fields,
liquid droplets of certain materials will undergo solidification, forming
crystallites at temperature and pressure conditions that correspond to liquid
droplets at field-free conditions. This electric-field-induced phase
transformation is termed electrocrystallization and was performed at the Georgia Institute of Technology,

Intro: 

Physicists
have predicted that under the influence of sufficiently high electric fields,
liquid droplets of certain materials will undergo solidification, forming
crystallites at temperature and pressure conditions that correspond to liquid
droplets at field-free conditions. This electric-field-induced phase
transformation is termed electrocrystallization and was performed at the Georgia Institute of Technology,

Alumni: 

Physics Professors Awarded CAREER Awards

Wednesday, October 5, 2011

School of Physics Assistant Professors Markus Kindermann and Daniel Goldman have been awarded National Science Foundation Faculty Early Career Development (CAREER) Awards.

Dr. Goldman's (pictured at left) award will support his research on the "Discovery and Dissemination of Neuromechanical Principles of Swimming, Walking and Running in Granular Media."

Dr. Kindermann's (pictured at right) award will support his research on "Interactions and Entanglement in Electronic Nanostructures."

The Faculty Early Career Development (CAREER) Program is a Foundation-wide activity that offers the National Science Foundation's most prestigious awards in support of junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research within the context of the mission of their organizations. Such activities should build a firm foundation for a lifetime of leadership in integrating education and research.

Summary: 

School of Physics professors Markus Kindermann and Daniel Goldman have been awarded National Science Foundation Faculty Early Career Development (CAREER) Awards.

Intro: 

School of Physics professors Markus Kindermann and Daniel Goldman have been awarded National Science Foundation Faculty Early Career Development (CAREER) Awards.

Alumni: 

2011 Nobel Prize in Physics

Tuesday, October 4, 2011

The Nobel Prize in Physics 2011 was awarded "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae" with one half to Saul Perlmutter and the other half jointly to Brian P. Schmidt and Adam G. Riess.

The Royal Swedish Academy of Sciences said American Saul Perlmutter would share the 10 million kronor ($1.5 million) award with U.S.-Australian Brian Schmidt and U.S. scientist Adam Riess. Working in two separate research teams during the 1990s -- Perlmutter in one and Schmidt and Riess in the other -- the scientists raced to map the universe's expansion by analyzing a particular type of supernovas, or exploding stars.

Summary: 

Three US-born scientists won the Nobel Prize in physics Tuesday for discovering that the universe is expanding at an accelerating pace.

Intro: 

Three US-born scientists won the Nobel Prize in physics Tuesday for discovering that the universe is expanding at an accelerating pace.

Alumni: 

Emeritus Prof. Eugene Patronis receives 2011 Fellowship to the Audio Engineering Society

Monday, August 29, 2011

Congratulations to Emeritus Professor Eugene Patronis on receiving the 2011 Fellowship award from the Audio Engineering Society!

The Fellowship Award is given to a member who had rendered conspicuous service or is recognized to have made a valuable contribution to the advancement in or dissemination of knowledge of audio engineering or in the promotion of its application in practice.

He is now Professor Emeritus of Physics at the Georgia Institute of Technology where he taught and performed research for fifty-one years. During his teaching career he founded programs in applied physics in the areas of acoustics, electronic instrumentation, and computer interfacing. In addition to numerous refereed scientific publications dealing with nuclear physics, electronics, acoustics, and audio, he has authored chapters in five reference handbooks dealing with nuclear physics, electronics, and audio engineering.

Summary: 

Congratulations to Emeritus Professor Eugene Patronis on receiving the 2011 Fellowship award from the Audio Engineering Society!

Intro: 

Congratulations to Emeritus Professor Eugene Patronis on receiving the 2011 Fellowship award from the Audio Engineering Society!

Alumni: 

Oct. 22: Prof. Ignacio Taboada speaks at the Atlanta Science Tavern: Cool Neutrino Astrophysics at the South Pole

Saturday, October 22, 2011

IceCube is gigantic detector, about 400 times the volume of the great pyramid of Giza, that operates at the geographic South Pole. By finding and studying ghost-like neutrino particles, IceCube will open a new window into the Universe and may solve the century-old question of the origin of cosmic rays. Ignacio's talk will describe the operation of IceCube, life at the South Pole, what neutrinos and cosmic rays are and how IceCube uses neutrinos to study the cosmos.

For more information see the Atlanta Science Tavern page.

Summary: 

Prof. Ignacio Taboada speaks at the Atlanta Science Tavern: Cool Neutrino Astrophysics at the South Pole

Intro: 

Prof. Ignacio Taboada speaks at the Atlanta Science Tavern: Cool Neutrino Astrophysics at the South Pole

Alumni: 

Walter de Heer has been named as the first recipient of the Utz-Hellmuth Felcht Award

Tuesday, August 16, 2011

Regents’ Professor Walter de Heer is recognized for his invention of graphene based electronics –“Carbon Based Solutions for Urban Life” in Shanghai / Wiesbaden on July 29, 2011.

SGL Group—The Carbon Company has awarded the Utz-Hellmuth Felcht Award for the first time at the International Carbon Conference in Shanghai. This prestigious donation of €20,000 will be awarded by SGL Group every two years in honor of its former Supervisory Board Chairman Prof. Utz-Hellmuth Felcht. Honored will be outstanding scientific and technological contributions in the field of carbon and ceramic materials.

The first winner of the Felcht Award is Professor Walter de Heer from the Georgia Institute of Technology in Atlanta, Georgia for his merits in the area of graphene research and his revolutionary concept of graphene based nanoelectronics.

Dr. Gerd Wingefeld, member of the Board of Management of SGL Group, responsible for Technology and Innovation: “The challenges of our time are global: Energy production from alternative sources, energy storage and energy efficiency. Carbon in its various forms and applications can contribute mastering these challenges. Through his work on electronic transportation mechanisms in graphene, Prof. Walter de Heer opened the door to a new era of extremely small electronic circuits.”

Individual graphite layers are known as graphene. In 2010, Konstantin Novoselov and Andre Geim were awarded with the Nobel Prize in Physics for their contributions in the field of electrical properties of the thinnest graphite layers. Graphene has the potential to replace silicon in electronics for applications such as ultra-high frequency electronics. At the time, SGL Group presented its “Carbon Based Solutions for Urban Life” concept, which focuses on innovative applications and sustainable solutions through the use of carbon-based products – from electromobility to lightweight solutions, energy efficient infrastructures and cooling systems in buildings.

In general, the Award will honor a single scientific and technological contribution which provided recent impact of significance on manufacturing and application or has the character of a breakthrough in science.

The Utz-Hellmuth Felcht Award will be presented biennially on the occasion of the International Carbon Conferences held alternately in Asia, Europe, and the USA.  The selection of the awardees is dedicated to an International Award Committee composed of six renowned scientists and persons of high standing in industry.

Summary: 

Regents’ Professor Walter de Heer is recognized for his invention of graphene based electronics –“Carbon Based Solutions for Urban Life” in Shanghai / Wiesbaden on July 29, 2011.

Intro: 

Regents’ Professor Walter de Heer is recognized for his invention of graphene based electronics –“Carbon Based Solutions for Urban Life” in Shanghai / Wiesbaden on July 29, 2011.

Alumni: 

Mechanical models of sandfish locomotion reveal principles of high performance subsurface sand-swimming

Tuesday, August 9, 2011

Assistant Professor Daniel Goldman and his group integrated biological experiment, empirical theory, numerical simulation and a physical model to reveal principles of undulatory locomotion in granular media. High-speed X-ray imaging of the sandfish lizard showed that it swims within the medium without using its limbs by propagating a single-period travelling sinusoidal wave down its body. Using these models and analytical solutions of the RFT, they varied the ratio of undulation amplitude to wavelength (A/λ) and demonstrate an optimal condition for sand-swimming, which for a given A results from the competition between η and λ.  J. R. Soc. Interface, September 7, 2011 8:1332-1345.

Summary: 

Mechanical models of sandfish locomotion reveal principles of high performance subsurface sand-swimming

Intro: 

Mechanical models of sandfish locomotion reveal principles of high performance subsurface sand-swimming

Alumni: 

Heated AFM Tip Draws Ferroelectric Nanostructures Directly on Plastic

Wednesday, July 27, 2011

Using a technique known as thermochemical nanolithography (TCNL), researchers have developed a new way to fabricate nanometer-scale ferroelectric structures directly on flexible plastic substrates that would be unable to withstand the processing temperatures normally required to create such nanostructures.

The technique, which uses a heated atomic force microscope (AFM) tip to produce patterns, could facilitate high-density, low-cost production of complex ferroelectric structures for energy harvesting arrays, sensors and actuators in nano-electromechanical systems (NEMS) and micro-electromechanical systems (MEMS). The research was reported July 15 in the journal Advanced Materials.

"We can directly create piezoelectric materials of the shape we want, where we want them, on flexible substrates for use in energy harvesting and other applications," said Nazanin Bassiri-Gharb, co-author of the paper and an assistant professor in the School of Mechanical Engineering at the Georgia Institute of Technology. "This is the first time that structures like these have been directly grown with a CMOS-compatible process at such a small resolution. Not only have we been able to grow these ferroelectric structures at low substrate temperatures, but we have also been able to pattern them at very small scales."

The research was sponsored by the National Science Foundation and the U.S. Department of Energy. In addition to the Georgia Tech researchers, the work also involved scientists from the University of Illinois Urbana-Champaign and the University of Nebraska Lincoln.

The researchers have produced wires approximately 30 nanometers wide and spheres with diameters of approximately 10 nanometers using the patterning technique. Spheres with potential application as ferroelectric memory were fabricated at densities exceeding 200 gigabytes per square inch -- currently the record for this perovskite-type ferroelectric material, said Suenne Kim, the paper's first author and a postdoctoral fellow in laboratory of Professor Elisa Riedo in Georgia Tech's School of Physics.

To read the full article, please visit this site:  http://www.gatech.edu/newsroom/release.html?nid=68848

Summary: 

Researchers have developed a new way to fabricate nanometer-scale ferroelectric structures directly on flexible plastic substrates that would be unable to withstand the processing temperatures normally required to create such nanostructures.

Intro: 

Researchers have developed a new way to fabricate nanometer-scale ferroelectric structures directly on flexible plastic substrates that would be unable to withstand the processing temperatures normally required to create such nanostructures.

Alumni: 

Scientists Finely Control Methane Combustion to Get Different Products

Thursday, July 21, 2011

Scientists have discovered a method to control the gas-phase selective catalytic combustion of methane, so finely that if done at room temperature the reaction produces ethylene, while at lower temperatures it yields formaldehyde. The process involves using gold dimer cations as catalysts — that is, positively charged diatomic gold clusters. Being able to catalyze these reactions, at or below room temperature,  may lead to significant cost savings in the synthesis of plastics, synthetic fuels and other  materials. The research was conducted by scientists at the Georgia Institute of Technology and the University of Ulm. It appears in the April 14, 2011, edition of The Journal of Physical Chemistry C.

­The beauty of this process is that it allows us to selectively control the products of this catalytic system, so that if one wishes to create formaldehyde, and potentially methyl alcohol, one burns methane by tuning its reaction with oxygen to run at  lower temperatures, but if it’s ethylene  one is after,  the reaction can be tuned to run at room temperature,” said Uzi Landman, Regents’ and Institute Professor of Physics and director of the Center for Computational Materials Science at Georgia Tech.

Full article can be found here.

Summary: 

Scientists Finely Control Methane Combustion to Get Different Products

Intro: 

Scientists Finely Control Methane Combustion to Get Different Products

Alumni: 

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