as a corset improves the appearance of its wearer by keeping everything
tightly together, rigidly constraining insulating materials in
electrical components can increase their energy density and decrease
their rates of failure.
electrical components, like wiring, are typically surrounded by a
material that keeps the electricity from passing to its surroundings.
These insulating materials are known as dielectrics, and can take many
forms, with the most common being “soft” materials known as polymers.
However, since these dielectrics are constantly being submitted to
electrical voltage, they tend to break down.
University engineers have demonstrated that rigidly constraining
dielectric materials can greatly improve their performance and
potentially lengthen their lifespans. This insight follows their
discovery earlier this year of the exact mechanism that causes soft
dielectric materials to break down in the presence of electricity.
found that increasing voltage can cause polymers to physically crease
and even crater at the microscopic level, eventually causing them to
break down,” said Xuanhe Zhao, assistant professor of mechanical
engineering and materials science at Duke’s Pratt School of Engineering.
“So we thought if we wrapped the polymer tightly, that would prevent
this creasing from occurring. Experiments proved this hypothesis to be
The results of the Duke study were published online in the journal Applied Physical Letters.
their experiments, the Duke researchers constrained three different
soft polymer dielectrics with epoxy. Epoxy is a type of polymer created
by the reaction of a resin with a hardening agent. When mixed, a hard
and inflexible coating is formed.
rigid epoxy acts as a mechanical constraint,” Zhao said. “Since it
adheres tightly to the dielectric, it prevents the deformation that
would normally occur. We found that this constraint can greatly enhance
the ability of the component to carry greater voltage, increasing its
energy density by more than ten times.”
said that scientists have been working for years to develop new
dielectrics based on new types of soft materials or polymers to increase
energy density and solve the problem of breakdown.
believe that there can be a drastically different approach to achieving
these higher energy-dense soft dielectrics,” Zhao said. “Our
experiments show that the energy density of these soft materials can be
significantly enhanced by proper mechanical constraints of the
dielectrics, and not necessarily a new type of dielectric material.”
team is currently testing newer methods for achieving even tighter
constraints to increase the energy density of polymer dielectrics.
research was supported by startup funds from Pratt and the Triangle
Materials Research Science and Engineering Center, which is funded by
the National Science Foundation.
Other Duke members of the team were students Lin Zhang and Qiming Wang.
Mechanical constraints enhance electrical energy densities of soft dielectrics