Bandage is threaded with photonic fibers that change color to signal pressure level.
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. Compression stockings and bandages, wrapped tightly around the affected limb, can help to stimulate blood flow. But there is currently no clear way to gauge whether a bandage is applying an optimal pressure for a given condition.
Now engineers at MIT have developed pressure-sensing photonic fibers that they have woven into a typical compression bandage. 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, say, wrapping it around a patient’s leg.
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.
“Getting the pressure right is critical in treating many medical conditions including venous ulcers, which affect several hundred thousand patients in the U.S. each year,” says Mathias Kolle, assistant professor of mechanical engineering at MIT. “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.”
Kolle and his colleagues have published their results in the journal Advanced Healthcare Materials. Co-authors from MIT include first author Joseph Sandt, Marie Moudio, and Christian Argenti, along with J. 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.
The color of the photonic fibers arises not from any intrinsic pigmentation, but from their carefully designed structural configuration. Each fiber is about 10 times the diameter of a human hair. 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.
In this rolled-up configuration, 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, for instance red, while diminishing the brightness of other colors. This makes the fiber appear a certain color, depending on the thickness of the layers within 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.”
The fibers’ design relies upon an optical phenomenon known as “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. Optical interference is what produces colorful swirls in oily puddles and soap bubbles. It’s also what gives peacocks and butterflies their dazzling, shifting shades, as their feathers and wings are made from similarly periodic structures.
“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.
A multilayered approach
The team’s approach combines known optical design concepts with soft materials, to create dynamic photonic materials.
While a postdoc at Harvard in the group of Professor Joanna Aizenberg, Kolle was inspired by the work of Pete Vukusic, professor of biophotonics at the University of Exeter in the U.K., on Margaritaria nobilis, a tropical plant that produces extremely shiny blue berries. The fruits’ skin is made up of cells with a periodic cellulose structure, through which light can reflect to give the fruit its signature metallic blue color.
Together, Kolle and Vukusic sought ways to translate the fruit’s photonic architecture into a useful synthetic material. Ultimately, they fashioned multilayered fibers from stretchable materials, and assumed that stretching the fibers would change the individual layers’ thicknesses, enabling them to tune the fibers’ color. The results of these first efforts were published in Advanced Materials in 2013.
When Kolle joined the MIT faculty in the same year, he and his group, including Sandt, improved on the photonic fiber’s design and fabrication. In their current form, the fibers are made from layers of commonly used and widely available transparent rubbers, wrapped around highly stretchable fiber cores. Sandt fabricated each layer using spin-coating, a technique in which a rubber, dissolved into solution, is poured onto a spinning wheel. Excess material is flung off the wheel, leaving a thin, uniform coating, the thickness of which can be determined by the wheel’s speed.
For fiber fabrication, Sandt formed these two layers on top of a water-soluble film on a silicon wafer. He then submerged the wafer, with all three layers, in water to dissolve the water-soluble layer, leaving the two rubbery layers floating on the water’s surface. Finally, he carefully rolled the two transparent layers around a black rubber fiber, to produce the final colorful photonic fiber.
The team can tune the thickness of the fibers’ layers to produce any desired color tuning, using standard optical modeling approaches customized for their fiber design.
“If you want a fiber to go from yellow to green, or blue, we can say, ‘This is how we have to lay out the fiber to give us this kind of [color] trajectory,’” Kolle says. “This is powerful because you might want to have something that reflects red to show a dangerously high strain, or green for ‘ok.’ We have that capacity.”
The team fabricated color-changing fibers with a tailored, strain-dependent color variation using the theoretical model, and then stitched them along the length of a conventional compression bandage, which they previously characterized to determine the pressure that the bandage generates when it’s stretched by a certain amount.
The team used the relationship between bandage stretch and pressure, and the correlation between fiber color and strain, to draw up a color chart, matching a fiber’s color (produced by a certain amount of stretching) to the pressure that is generated by the bandage.
To test the bandage’s effectiveness, Sandt and Moudio enlisted over a dozen student volunteers, who worked in pairs to apply three different compression bandages to each other’s legs: a plain bandage, a bandage threaded with photonic fibers, and a commercially-available bandage printed with rectangular patterns. This bandage is designed so that when it is applying an optimal pressure, users should see that the rectangles become squares.
Overall, the bandage woven with photonic fibers gave the clearest pressure feedback. Students were able to interpret the color of the fibers, and based on the color chart, apply a corresponding optimal pressure more accurately than either of the other bandages.
The researchers are now looking for ways to scale up the fiber fabrication process. Currently, they are able to make fibers that are several inches long. Ideally, they would like to produce meters or even kilometers of such fibers at a time.
“Currently, the fibers are costly, mostly because of the labor that goes into making them,” Kolle says. “The materials themselves are not worth much. If we could reel out kilometers of these fibers with relatively little work, then they would be dirt cheap.”
Then, such fibers could be threaded into bandages, along with textiles such as athletic apparel and shoes as color indicators for, say, muscle strain during workouts. Kolle envisions that they may also be used as remotely readable strain gauges for infrastructure and machinery.
“Of course, they could also be a scientific tool that could be used in a broader context, which we want to explore,” Kolle says.
The Latest on: Pressure-sensing photonic fibers
via Google News
The Latest on: Pressure-sensing photonic fibers
- Physics and applications of Raman distributed optical fiber sensingon May 13, 2022 at 10:06 am
Raman distributed optical fiber sensing has been demonstrated to be a mature and versatile scheme that presents great flexibility and effectivity for the distributed temperature measurement of a ...
- Novel Polymers Ease Fabrication of Optical Interconnectson May 10, 2022 at 5:00 pm
Researchers have developed new polymer materials for the advancement of optical sensing for the development ... links necessary to connect chip-based photonic components with board-level circuits or ...
- Distributed Fiber Optic Sensor (DFOS) Market size is to reach USD 987.4 million by 2028 with a CAGR of 8.7%| Valuates Reportson May 6, 2022 at 8:59 am
The growing use of DFOS in the power industry, bridges and tunnels, the petrochemical industry, and security monitoring is expected to propel the Distributed Fiber Optic Sensor (DFOS) Market forward.
- Distributed Fiber Optic Sensor (DFOS) Market size is to reach USD 987.4 million by 2028 with a CAGR of 8.7%| Valuates Reportson May 6, 2022 at 8:19 am
BANGALORE, India, May 6, 2022 /PRNewswire/ -- The Global Distributed Fiber Optic Sensor Market Segmented ... vibrations, pressure changes, and impacts throughout their entire length.
- Distributed Fiber Optic Sensor (DFOS) Market size is to reach USD 987.4 million by 2028 with a CAGR of 8.7%| Valuates Reportson May 6, 2022 at 6:02 am
BANGALORE, India, May 6, 2022 /PRNewswire/ -- The Global Distributed Fiber Optic Sensor Market Segmented by Type (DTS,DAS) by Application (Petroleum and Petrochemical, Power, Bridges and Tunnels ...
- Advances in femtosecond laser direct writing of fiber Bragg gratings in multicore fibers: technology, sensor and laser applicationson May 5, 2022 at 12:05 pm
Advances in femtosecond laser direct writing of fiber Bragg gratings in multicore fibers: technology, sensor and laser applications A new publication from Opto-Electronic Advances; DOI ...
- Research on the photonic crystal topological state beyond the optical diffraction limiton May 5, 2022 at 9:42 am
photonic-crystal fibers, optical sensors, etc. One of the major difficulties in the photonic crystal manufacturing process is the defect, which can cause the scattering of light that is propagated ...
- Photonic Sensors Market to Reach $94.26 Bn, Globally, by 2030 at 16.8% CAGR: AMR'on April 25, 2022 at 9:03 am
April 25, 2022 /PRNewswire/ -- Allied Market Research recently published a report, titled, 'Photonic Sensors Market by Product (Fiber Optic ... Position Sensor, and Pressure Sensor) and End ...
- Photonic Sensors Market to Reach $94.26 Bn, Globally, by 2030 at 16.8% CAGR: AMRon April 25, 2022 at 6:01 am
The fiber optic sensor segment held the largest share By product, the fiber optic sensor segment held the largest share in 2020, accounting for more than one-third of the global photonic sensors ...
via Bing News