With enough layers of consistent thickness, these reflections interact to strengthen some colors in the visible spectrum, for instance red, while diminishing the brightness of other colors. In this rolled-up configuration, light reflects off each interface between individual layers. Each layer within the roll is only a few hundred nanometers thick. The researchers fabricated the fiber from ultrathin layers of transparent rubber materials, which they rolled up to create a jelly-roll-type structure. Each fiber is about 10 times the diameter of a human hair. The color of the photonic fibers arises not from any intrinsic pigmentation, but from their carefully designed structural configuration. Kenji Clark of the Univeristy of Tokyo, James Hardin of the United States Air Force Research Laboratory, Matthew Carty of Brigham and Women’s Hospital-Harvard Medical School, and Jennifer Lewis of Harvard University. Co-authors from MIT include first author Joseph Sandt, Marie Moudio, and Christian Argenti, along with J. Kolle and his colleagues have published their results in the journal Advanced Healthcare Materials. We can design them so that for a specific desired pressure, the fibers reflect an easily distinguished color.” “These fibers can provide information about the pressure that the bandage exerts.
each year,” says Mathias Kolle, assistant professor of mechanical engineering at MIT. “Getting the pressure right is critical in treating many medical conditions including venous ulcers, which affect several hundred thousand patients in the U.S. The photonic fibers can then serve as a continuous pressure sensor - if their color changes, caregivers or patients can use the color chart to determine whether and to what degree the bandage needs loosening or tightening. Using a color chart, a caregiver can stretch a bandage until it matches the color for a desired pressure, before, say, wrapping it around a patient’s leg. As the bandage is stretched, the fibers change color. Now engineers at MIT have developed pressure-sensing photonic fibers that they have woven into a typical compression bandage. But there is currently no clear way to gauge whether a bandage is applying an optimal pressure for a given condition. Compression stockings and bandages, wrapped tightly around the affected limb, can help to stimulate blood flow.
Compression therapy is a standard form of treatment for patients who suffer from venous ulcers and other conditions in which veins struggle to return blood from the lower extremities.
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