Compression stockings and bandages are essential elements in the treatment of various medical conditions, and applying the optimal pressure to stimulate blood flow for a given condition is a key to successful treatment. Now a team of MIT engineers led by assistant professor Mathias Kolle has developed pressure-sensing photonic fibers that some day may be woven into a typical compression bandage.
A recent MIT release says that as the bandage is stretched, the fibers change color. Using a color chart, a caregiver can stretch a bandage until it matches the color for a desired pressure before wrapping it around a patient’s leg, for example. The photonic fibers can then serve as a continuous pressure sensor; if the color changes, caregivers or patients can use the color chart to determine if the bandage needs loosening or tightening and to what degree.
The color of the photonic fibers arises from the fiber’s structure. The researchers fabricated the fiber from ultrathin layers of transparent rubber materials, which they rolled up to create a jelly roll-type structure. Each layer within the roll is only a few hundred nanometers thick; each fiber is about 10 times the diameter of a human hair.
In this rolled-up configuration, the release says, light reflects off each interface between individual layers. With enough layers of consistent thickness, these reflections interact to strengthen some colors in the visible spectrum, while diminishing the brightness of other colors.
The fibers’ design relies on the optical phenomenon of “interference,” in which light, reflected from a periodic stack of thin, transparent layers, can produce vibrant colors that depend on the stack’s geometric parameters and material composition. The team can alter the thickness of the fibers’ layers to produce any desired color tuning.
The researchers are now looking for ways to scale up the fiber fabrication process. Currently, they are able to make fibers several inches long. Once scalable, the team imagines the fibers could be threaded into bandages, as well as textiles for athletic apparel and shoes as color indicators for muscle strain during workouts. Kolle envisions that the photonic fibers may also be used as remotely readable strain gauges for infrastructure and machinery.
This research was supported in part by the National Science Foundation and the MIT Dept. of Mechanical Engineering.