Crystals and ceramics pale
when compared to a material researchers at Oak Ridge National Laboratory
discovered that has 10 times their piezoelectric effect, making it suitable for
perhaps hundreds of everyday uses.
ORNL's Volker Urban and colleagues at Technical
University Aachen in Germany
noticed the reverse piezoelectric effect—defined as creating a mechanical
strain by applying an electrical voltage—while conducting fundamental research
on polymers. At first they didn't think about their observations in terms of
classic piezoelectric materials, but then they became more curious.
"We thought about comparing the effects
that we observed to more 'classic' piezoelectric materials and were surprised
by how large the effects were by comparison," says Urban, a member of the
Department of Energy lab's Neutron Scattering Science Division.
Until now, scientists did not believe that
non-polar polymers were capable of exhibiting any piezoelectric effect, which
occurs only in non-conductive materials. This research, however, shows up to 10
times the measured electro-active response as compared to the strongest known
piezoelectric materials, typically crystals and ceramics.
"We observed this effect when two
different polymer molecules like polystrene and rubber are coupled as two
blocks in a di-block copolymer," Urban says.
Temperature-dependent studies of the
molecular structure revealed an intricate balance of the repulsion between the
unlike blocks and an elastic restoring force found in rubber. The electric
field adds a third force that can shift the intricate balance, leading to the
piezoelectric effect.
"The extraordinarily large response
could revolutionize the field of electro-active devices," says Urban, who
listed a number of examples, including sensors, actuators, energy storage
devices, power sources, and biomedical devices. Urban also noted that
additional potential uses are likely as word of this discovery gets out and additional
research is performed.
"Ultimately, we're not sure where this
finding will take us, but at the very least it provides a fundamentally new
perspective in polymer science," Urban says.
The paper, titled "Piezoelectric
Properties of Non-Polar Block Copolymers," was published in Advanced Materials.
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