ORNL researchers detected for the first time ferroelectric domains (seen as red stripes) in the simplest known amino acid—glycine. |
The boundary
between electronics and biology is blurring with the first detection by
researchers at United States Department of Energy’s Oak Ridge National
Laboratory of ferroelectric properties in an amino acid called glycine.
A
multi-institutional research team led by Andrei Kholkin of the University of
Aveiro, Portugal, used a combination of experiments and modeling to identify
and explain the presence of ferroelectricity, a property where materials switch
their polarization when an electric field is applied, in the simplest known
amino acid—glycine.
“The
discovery of ferroelectricity opens new pathways to novel classes of
bioelectronic logic and memory devices, where polarization switching is used to
record and retrieve information in the form of ferroelectric domains,”
said coauthor and senior scientist at ORNL’s Center for Nanophase Materials Sciences
(CNMS) Sergei Kalinin.
Although certain
biological molecules like glycine are known to be piezoelectric, a phenomenon
in which materials respond to pressure by producing electricity,
ferroelectricity is relatively rare in the realm of biology. Thus, scientists
are still unclear about the potential applications of ferroelectric
biomaterials.
“This
research helps paves the way toward building memory devices made of molecules
that already exist in our bodies,” Kholkin said.
For example,
making use of the ability to switch polarization through tiny electric fields
may help build nanorobots that can swim through human blood. Kalinin cautions that such nanotechnology is
still a long way in the future.
“Clearly
there is a very long road from studying electromechanical coupling on the
molecular level to making a nanomotor that can flow through blood,” Kalinin said. “But
unless you have a way to make this motor and study it, there will be no second
and third steps. Our method can offer an option for quantitative and
reproducible study of this electromechanical conversion.”
The study,
published in Advanced Functional
Materials, builds on previous research at ORNL’s CNMS, where Kalinin and
others are developing new tools such as the piezoresponse force microscopy used
in the experimental study of glycine.
“It turns
out that piezoresponse force microsopy is perfectly suited to observe the fine
details in biological systems at the nanoscale,” Kalinin said. “With this type of
microscopy, you gain the capability to study electromechanical motion on the
level of a single molecule or small number of molecular assemblies. This scale
is exactly where interesting things can happen.”
Kholkin’s laboratory
grew the crystalline samples of glycine that were studied by his team and by
the ORNL microscopy group. In addition to the experimental measurements, the
team’s theorists verified the ferroelectricity with molecular dynamics
simulations that explained the mechanisms behind the observed behavior.
