A chemical strip changes color to show the force of an impact.
When the Steelers and Patriots clash on Thursday night in football's season opener, you'll see 250-pound men slam into each other, head to head, at high speed.
And get concussions?
There's no easy way to tell. That goes for young athletes, too, whose developing brains are particularly vulnerable to damage if they keep playing after getting a concussion. Sports-related brain trauma sends a quarter-million American kids to the emergency room annually, but symptoms may unfold over hours, days, or even weeks.
A material developed at the University of Pennsylvania may eventually help detect when a hit is hard enough to damage the brain. Researchers led by Shu Yang have created a chemical strip that changes color on impact to measure the force of a collision. The material could be integrated into helmets for athletes or soldiers. The goal is to make something akin to litmus paper, which changes color according to acidity, to show the severity of football tackles or bomb blasts.
There's already a small industry trying to develop helmet sensors and other devices to measure or prevent concussions in sports, though it hasn't yielded breakthroughs yet. A contest by the National Football League and General Electric is funding approaches to detect brain injuries with blood tests and imaging.
The problem is determining what really happens to the brain on impact. "No one’s been able to predict in clinical cases how much force it actually takes to cause a concussion," said the Cleveland Clinic's Richard Figler, former team physician for the Browns. 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.
The University of Pennsylvania technology needs further research to show whether it can accurately predict injuries, rather than just measure the force of a hit. Still, it might become an elegant tool built into helmets. The material relies on tiny crystals whose color is linked to their underlying shapes, not to pigmentation. The same kind of “structural color” produces the iridescence in butterfly wings and peacock feathers. When a hard blow changes the shape of the crystals, the color changes as well.
“It’s a very porous, Swiss-cheese like structure,” said Yang, a 45-year-old veteran of Bell Labs. “If you provide external force, very high force, the structure basically is cracked open, damaged.”
Microscope images show crystals changing color at three levels of force. The more powerful impacts on the right leave larger, darker marks. Source: Yang Lab via Bloomberg
Yang’s team and colleagues at Villanova University tested the material with a tiny probe that can apply a carefully controlled amount of force. Then they examined it under a microscope to record color changes. Different levels of force turned the crystals green or purple, about the equivalent of a vehicle hitting a brick wall at 80 miles per hour.
One challenge will be to measure the speed of an impact, because the same force can be much more damaging to neurons at higher speeds. “Imagine Silly Putty,” Yang said. “If you stretch slowly, you will not break it. But if you stretch very fast, it will break quickly.”
While most people fully recover from a single concussion, successive injuries can raise the risk of lasting brain damage and have been linked to depression. Many parents and coaches are already trained to recognize the signs of a concussion, such as memory problems, sluggishness, or headaches that follow a blow, but players can hide symptoms to stay in a game. Any tool that can help accurately identify when a concussion has occurred would be a welcome advance because "the brain is in a heightened state of vulnerability after it’s been injured," said Gerard Gioia, chief of neuropsychology at Children's National Health System in Washington. "The earlier we can detect this problem, the safer that individual will be."