SMART MATERIALS—MATERIALS THAT ADAPT TO CHANGING CONDITIONS - Chemistry: Notable Research and Discoveries - page 123

materials are made of long chains of bonded molecules that form du-
rable fibers. Although natural fibers continue to be used, many clothes
today are made from synthetic materials.
If “smart fibers” began to be widely used, perhaps clothes and oth-
er fabrics would become more adaptable. Nature is one place to look
for inspiration. Olivier Emile and Albert Le Floch of the Université de
Rennes in France and Fritz Vollrath at Oxford University in England
studied why spiders rarely spin around when hanging from their silk
threads. Most fibers turn and twist, as a climber dangling from a rope
knows all too well, yet a suspended spider is stable. The researchers dis-
covered that spider silk has a kind of shape memory in which it rapidly
recovers its shape, resisting any twisting motion. This research, “Shape
Memory in Spider Draglines,” was published in Nature in 2006.
Researchers who study polymers are looking for novel ways to in-
corporate shape memory into these materials. Shape-memory polymers
that respond to heat have been discovered, and in 2005, Andreas Lend-
lein at the Institute of Polymer Research in Teltow, Germany, Massa-
chusetts Institute of Technology researcher Robert Langer, and their
colleagues found a shape-memory polymer that is responsive to light.
As reported in “Light-Induced Shape-Memory Polymers,” published in
Nature in 2005, this smart polymer is composed of certain chemical
groups that are sensitive to light. Exposure to light induces the poly-
mer's molecules to bond, cross-linking and stabilizing the structure in
a specific shape. Light of different wavelength can break the bonds, re-
turning the polymer to its original shape.
Smart fibers can make smart sutures—threads used by surgeons
to sew up incisions—such as suture that ties itself when heated! And
Sensatex Incorporated makes a smart shirt that automatically monitors
the wearer's vital signs. Special sensors and conducting fibers embed-
ded in the shirt measure heart rate, respiration, and body temperature,
and a tiny controller relays this information by transmitter to a medical
station.
AdAPTABlEAIrPlAnES
One of the most heavily researched applications for smart materials in-
volves aviation. The marvelous adaptability of the wings of peregrine
falcons means that the bird is proficient in both soaring and diving.