Photo: Computational model of the composite bending in response to light.
(December 14, 2015) Combining
photo-responsive fibers with thermo-responsive gels, researchers at the
University of Pittsburgh’s Swanson School of Engineering and Clemson University
have modeled a new hybrid material that could reconfigure itself multiple times
into different shapes when exposed to light and heat, allowing for the creation
of devices that not only adapt to their environment, but also display
distinctly different behavior in the presence of different stimuli.
Computational modeling developed by Anna C. Balazs,
Distinguished Professor of Chemical and Petroleum Engineering at Pitt, and Olga
Kuksenok, Associate Professor of Materials Science and Engineering at Clemson's
College of Engineering and Science, predicted these composites would be both
highly reconfigurable and mechanically strong, signaling a potential for
biomimetic four-dimensional printing. Their research, “Stimuli-responsive
behavior of composites integrating thermo-responsive gels with photoresponsive
fibers,” was recently published in the journal Materials Horizons, published by
the Royal Society of Chemistry (DOI: 10.1039/C5MH00212E).
“In 4D printing, time is the fourth dimension that characterizes
the structure of the material; namely, these materials can change shape even
after they have been printed. The
ability of a material to morph into a new shape alleviates the need to build a
new part for every new application, and hence, can lead to significant cost
savings,” Dr. Balazs explained. “The challenge that researchers have faced is
creating a material that is both strong and malleable and displays different
behavior when exposed to more than one stimulus.”
Drs. Balazs and Kuksenok resolved this issue by embedding
light-responsive fibers, which are coated with spirobenzopyran (SP)
chromophores, into a temperature-sensitive gel. This new material displays
distinctly different behavior in the presence of light and heat.
“If we anchor a sample of the composite to a surface, it
will bend in one direction when exposed to light, and in the other direction
when exposed to heat,” Dr. Kuksenok said. “When the sample is detached, it
shrinks like an accordion when heated and curls like a caterpillar when
illuminated. This programmable behavior allows a single object to display
different shapes and hence functions, depending on how it is exposed to light
or heat.”