Color-Changing Polymer-Based Material Could Help Detect Traumatic Brain Injuries

Researchers at the University of Pennsylvania have developed a new polymer-based material that is capable of changing colors based on the speed of impact inflicted on it to detect risk of brain damage.

Microscopy images of the photonic crystals after nano-indentation at 30 mN (left), 60 mN (middle) and 90 mN (right) are shown. Credit:Yang lab

It is hoped that these polymers will one day be incorporated into helmets and other head gear so that, when struck, the level of risk of brain damage will be immediately clear.

The researchers will describe their new technique in one of over 9,000 presentations to be delivered at the American Chemical Society (ACS)’s 250th National Meeting & Exposition to be held from 16 to 20 August, 2015.

A rough tackle or a bomb blast can severely damage the brain, but at the time of impact, such injuries are not often seen. New studies and media reports have suggested that professional athletes and soldiers may experience dementia, headaches, memory loss and long-term complications that arise from past head trauma.

Earlier in April, a team of National Football League players filed a lawsuit demanding the organization to make payments to retired players who had head injuries. This lawsuit was eventually settled. In fact, a number of professional hockey players are filing a lawsuit against the National Hockey League regarding the same problem.

At present, there is no clear way to find out whether someone has suffered a brain injury. As a result, athletes and soldiers may inadvertently continue to perform the very same activity that inflicted the damage and possibly cause more injury.

Shu Yang, Ph.D., explained that a color-changing, force-responsive patch could eliminate further injury. "If the force was large enough, and you could easily tell that, then you could immediately seek medical attention," she explained.

Yang's team utilized holographic lithography to develop photonic crystals with intricately designed structures to impart a specific color to the crystals, similar to opals. When the crystals are deformed through an applied force, their internal structures change, thereby changing their color.

The material is lightweight and does not need power to detect forces, thus providing a suitable means for medical staff to detect a damaging force on-site without requiring a costly tool. However, Yang said that making these crystals is a costly process, and hence is unsuitable for large-scale production.

To overcome this issue, the researchers used self-assembly and polymer basede materials which cost less to produce on a large scale than the previous holographic lithography technique.

The initial step in the process was to shape the polymer into a structure that functioned similarly to the unique photonic crystals. In order to make a mold, the team combined different sizes of silica particles, allowing them to self-assemble into photonic crystals with the preferred pattern.

The polymer was then heated, causing it to infiltrate the mold, and then they let it solidify before removing the mold, leaving the inversed polymer crystals behind. Following this, the researchers applied different amounts of force to the polymer crystal and observed the change in color. The outcomes proved to be interesting.

"We were able to change the color consistently with certain forces," Yang said.

Cho added that when a 30 mN force was applied — roughly the force of a sedan travelling at 80 mph hitting into a brick wall — it made the crystal change its color from red to green. Similarly, when a 90 mN force was applied — equal to a speeding truck crashing the same wall — the crystal changed into a purple color.

"This force is right in the range of a blast injury or a concussion," Yang said.

Yang intends to carry out more studies where she would create new materials that would indicate the speed of a force applied and reveal how a specific trauma damages the brain.



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