Theory of Superconducting and Electromagnetic
Properties of Some Nanostructured Materials
David Stroud, Ohio State University
NSF DMR04-13395
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Research Highlight: Forces in
Electrorheological (ER) Fluids
An ER fluid is a material whose
viscosity (resistance to flow) can
be changed by an electric field
(e. g. with a battery).
They usually consist of
suspensions of dielectric
spheres in a host made of
another insulator.
If an electric field is applied, the
spheres line up, making the
suspension more viscous
(instead of behaving like water, it
becomes more like honey).
In our method, we connect the
forces to the optical properties
of the spheres.
SrTi03
E
Silicone oil
Two strontium titanate spheres (diameter 6.3
mm) in silicone oil are strongly attracted when
electric field E = 71 volts/mm is applied.
Force is strongly attractive and depends on
frequency. Spheres separated by only 0.1-0.3mm
Theory of Superconducting and Electromagnetic Properties of Some
Nanostructured Materials
David Stroud, Ohio State University
NSF DMR04-13395
Some potential applications:
1. Change in viscosity with applied
electric field gives a motor oil with
controllable thickness (already
used in car brakes).
2. At optical frequencies, if the
spheres are small and metallic,
rather than large and non-metallic,
the same principle can be used to
calculate the force between the
spheres induced by a strong light
beam.
Publications:
Kwangmoo Kim, David Stroud,
X. Li, D. J. Bergman, Phys. Rev.
E71, 031503 (2005); Li, Bergman and
Stroud, Europhys. Lett. 69, 1010
(2005).
Contributions to Education:
Six grad students (Kwangmoo Kim,
Daniel Valdez-Balderas, Ivan Tornes,
Kohjiro Kobayashi, Vishwesha
Guttal, Rakesh Tiwari), one postdoc
(Sung Yong Park), one undergrad
REU student (Bryan Chen) and
another undergrad (Stefan Natu) have
contributed to work on this grant.
Ivan Tornes is now a staff scientist at
Battelle; Park has a postdoc at
Northwestern.
I have discussed ER fluids in my
graduate electromagnetism course,
including research findings from this
work.