By using exotic man-made materials,
scientists from Duke University and Boston College
believe they can greatly enhance the forces of electromagnetism (EM), one of
the four fundamental forces of nature, without harming living beings or
damaging electrical equipment.
This theoretical finding could have
broad implications for such applications as magnetic levitation trains, which
ride inches above the surface without touching it and are propelled by magnets
receiving electrical current.
As the term indicates, EM is made up
of two types of fields—electric and magnetic. Alternating current sources
generate both electric and magnetic fields, and increasing one of them
generally leads to the increase in the other. Electrical fields can cause
problems if they get too high.
“For any EM applications dealing with
things on the human scale, high-intensity EM fields needed for the generation
of strong EM forces interfere with other devices and may be harmful to
biological tissues, including humans,” said Yaroslav Urzhumov, assistant
research professor in electrical and computer engineering at Duke’s Pratt
School of Engineering.
“The severity of this problem is
substantially reduced if the fields are predominantly magnetic, since virtually
all biological substances and the majority of conventional materials are
transparent to magnetic fields,” Urzhumov said. “While we can’t suppress the
electric field completely, a magnetically active metamaterial could
theoretically reduce the amount of current needed to generate a high enough
magnetic field, thus reducing parasitic electric fields in the environment and
making high-power EM systems safer.”
The results of Urzhumov’s analysis
were published online in Physical Review
B, and the team’s research was supported by the Air Force Office of
The solution to this problem comes
from the recent ability to fabricate exotic composite materials known as
metamaterials, which are not so much a single substance, but an entire man-made
structure that can be engineered to exhibit properties not readily found in
nature. These metamaterials can be fabricated into a limitless array of sizes,
shapes, and properties depending on their intended use.
In the magnetic levitation train
example, conventional electromagnets could be supplemented by a metamaterial,
which would have been designed to produce significantly higher intensities of
magnetic fields using the same amount of electricity.
The Duke scientists came up with the
theoretical underpinning for the metamaterial, which is being fabricated by
collaborators at Boston
College, led by Willie
Padilla, associate professor of physics.
“The metamaterial should be able to
increase the magnetic force without increasing the electric current in the
source coil,” Urzhumov said. “The phenomenon of magnetostatic surface resonance
could allow magnetic levitation systems to increase the mass of objects being
levitated by one order of magnitude while using the same amount of
currently being used in a host of devices and applications, ranging from
subatomic optical tweezers scientists use to manipulate microscopic particles
with laser beams, to potentially highly destructive weapons.