Engineers Develop Compression Bandage That Changes Color to Indicate Pressure

Engineers at MIT have created color-changing compression bandages to ensure the pressure being applied is optimal. Compression bandages are used in to treat a variety of medical problems related to blood flow and circulation. 

They are often used to stimulate blood flow to a particular area, however, it is difficult to tell if the right amount of pressure has been applied. The MIT invention takes color-changing fibers and weaves them into compression bandages so that medical practitioners can get a visual check on the amount of pressure they have applied. 

Exact pressure crucial to good treatment

"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 get their color from their physical architecture. Each fiber is about 10 times the diameter of a human hair. The fibers are made from ultrathin layers of transparent rubber materials.

Each layer within the roll is only a few hundred nanometers thick. The rolled up design means light reflects off each ‘interface between individual layers.’ The reflections interact to enhance some color on the spectrum which makes the fiber look more like a certain color, depending on the thickness of the layers of the fiber. 

“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,” Sandt says. “These colors persist as long as the structure is maintained.” 

Learning from nature

The design takes its cues from nature, taking advantage of an optical phenomenon known as “interference”. When vibrant colors are produced from stacked very thin transparent layers, color and vibrancy depend on the stack’s geometric parameters and material composition. 

You see the phenomena occur in rainbows that appear in oily puddles and soap bubbles. It’s the same phenomenon that gives peacocks their incredibly colorful plumage. 

“My interest has always been in taking interesting structural elements that lie at the origin of nature’s most dazzling light manipulation strategies, to try recreating and employing them in useful applications,” Kolle says. 

The researchers then combined these fibers into a standard pressure bandage that they had ‘previously characterized to determine the pressure that the bandage generates when it’s stretched by a certain amount.’ They then drew up a chart that matched the fiber's color (produced by a certain amount of stretching) with the pressure that is generated by the bandage. 

By using this chart they could then create an indicator for other people to use the bandage. To test if their new color changing bandage worked, groups of volunteers tried three types of compression bandages on each other's legs. 

Volunteers found color bandage most effective to apply

The first was a standard bandage, the second was their fiber enhanced bandage and the third was a commercially-available bandage printed with rectangular patterns. The bandage is designed that when exerted to an optimal stretch, the pattern changes from rectangles to squares. 

The study concluded that the bandage woven with photonic fibers gave the most straightforward pressure feedback. The volunteers were able to match the colors of the fibers based on the chart and then bandage their fellow volunteers with greater accuracy than the other bandages. 

The scientists next step will be to reduce the cost of producing the fibers. Currently, the production takes a long time and requires high levels of labor. The full research can be read in Advanced Healthcare Materials.