A radical new hi-tech football helmet can change color if a player is at risk of a concussion.
As professional football players, Pop Warner and high school and college players hit the fields, researchers say that this technology could give an early warning of potential problems.
Shu Yang, a professor in the School of Engineering and Applied Science, has led a team of researchers in developing a polymer-based material that changes colors depending on how hard it is hit. The goal is to someday incorporate this material into protective headgear that could give an early warning sign of a concussion. “If the force was large enough, and you could see that as easy as reading a litmus test, then you could immediately seek medical attention,” Yang said.
“No one’s been able to predict in clinical cases how much force it actually takes to cause a concussion,” the Cleveland Clinic’s Richard Figler, former team physician for the Browns, told Bloomberg. Players caught off guard by a soccer ball kicked from behind, for example, can sustain concussions from much smaller forces than someone braced for a tackle, whose neck muscles absorb some of the blow. “The threshold is extremely wide,” Figler said.
Using holographic lithography – a laser-based method for patterning nanoscopic features into a three-dimensional material – Yang’s team has previously made photonic crystals that feature carefully designed internal structures. Like opals, these structures refract light into a particular color. Concussive force can deform the crystals, changing the arrangement of those structures and, thus, the crystal’s color.
In their new study, Yang and her colleagues developed an easier way of producing this effect that could hasten its adoption in consumer products like football helmets. The key difference was using a polymer that could be coaxed into forming the same internal structures as found in their specialized photonic crystals. First, the polymer was melted and poured into a mold consisting of silica beads. After the polymer solidified and the beads were removed, the polymer crystals were able to act as “inverse opals” and mimic these light-refracting features. The researchers then applied varying amounts of force to the polymer crystal and recorded the color change.
A strong hit caused it to change from red to green, while a stronger one changed it from red to purple. “The strength of these forces are right in the range of a blast injury or a concussion-causing hard tackle,” Yang said. The color change in the polymer version of the crystal is permanent. Once hit with high enough force, the crystal structure is permanently deformed, making it ideal for recording the strength of the impact – and ensuring damaged helmets are not reused.