Once a caregiver has stretched a patient's bandages enough to apply a certain amount of pressure, the photonic fibers can be used as a visual check on the amount of pressure the bandage is providing. "Getting the pressure right is critical in treating many medical conditions including venous ulcers, which affect several hundred thousand patients in the US each year," said MIT's Mathias Kolle in a statement. "These fibers can provide information about the pressure that the bandage exerts. We can design them so that for a specific desired pressure, the fibers reflect an easily distinguished color."
The fibers change color due to their structure, which consists of rolled up ultrathin layers of transparent rubber material. That way, light reflects off each individual layer which reflects specific wavelengths of light depending on thickness of the layers. When stretched, the layers thin out, reflecting different colors. "Structural color is really neat, because you can get brighter, stronger colors than with inks or dyes just by using particular arrangements of transparent materials," said Joseph Sandt, the first author on the paper. "These colors persist as long as the structure is maintained."