Colour-changing material could be used to signal traumatic brain injuries

The team, from the University of Pennsylvania, will present their discovery at the 250th National Meeting & Exposition of the American Chemical Society.

Head traumas such as those caused by bomb blasts on the battlefield and heavy tackles on the playing field have been identified as causing various long-term health problems, including dementia and memory loss.

Unfortunately, it can be difficult to immediately understand the full extent of head injuries, leading to many soldiers and athletes continuing to participate in activities that put them at further risk.

The researchers’ solution to this problem was to develop a material that responded to certain degrees of force by changing color, giving a visual indicator of the extent of damage that had been done.

“If the force was large enough, and you could easily tell that, then you could immediately seek medical attention,” states study co-author and postdoctoral researcher Shu Yang.

The team began by using a process called holographic lithography to develop crystals whose structures gave them specific colors. When force was applied, their internal structures were altered and subsequently their color changed.

Such crystals were lightweight and did not require power to function, making them well-suited to be used in protective equipment. However, the cost involved in manufacturing the crystals was high, rendering them unsuitable for mass production.

Material changes to different colors depending on how much force is applied

As an alternative, the team opted to use self-assembling polymers – chains of molecules that connect under certain conditions to form crystals with specific colors. Again, when applied force alters the internal structure of these crystals, the result is a change in color.

“The film can show the color change depending on how much and how quickly the force is applied,” explains co-author Younghyun Cho.

Applying a force of 30 millinewtons (mN) to the material – equivalent to a car at hitting a brick wall at 80 miles per hour – transformed the crystals’ color from red to green. In comparison, a force of 90 mN – equivalent to a truck hitting a brick wall – led to the crystals changing from red to purple.

Yang says that the forces that alter the color of the material range from a bomb blast to a concussion-causing impact on a sports field.

While these initial results are encouraging, there remains work to be done. Yang plans to further develop the materials at the team’s disposal so that they will be able to identify how quickly a specific force has been applied. The speed of impact is important to know as it affects the extent of the damage dealt to the brain.

Fast facts about traumatic brain injury

  • Concussion can be defined as an injury to the brain resulting from a blow or violent shaking
  • Traumatic brain injury contributes to around 30% of all injury deaths in the US
  • In 2010, around 2.5 million emergency department visits, hospitalizations or deaths were associated with traumatic brain injury. 


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