Trying to understand compression rather than stretching, Merrell combined a conductive nanoparticle mixture with foam.
He found that when compressed, the foam creates a voltage. The electrical signals can tell a coach exactly how hard a player has been hit and the extent of possible injury.
"A coach will know within seconds exactly how hard their player just got hit," Merrell said in a BYU news release. "Even if a player pops up and acts fine, the folks on the sidelines will have data showing that maybe he isn't OK."
Merrell is still working out a few issues in translating the voltage to the computer.
"We know the significance depends on force and acceleration, but we don't know the exact meaning of the voltage," he said. "We already have a prototype that works, we just need to refine it some more."
He and his colleagues hope to have the product ready in six to eight months, in time to enter it in the $10 million NFL Head Health Challenge. They're planning to sell the finished product for under $300, which Merrell said is lower than comparable systems that generally rely on accelerometers.
They started developing the foam in December, and concussions in football have only become a hotter issue since then. The dangers of repeated head injuries include an increased risk of anxiety, depression and suicide, said Craig Bryan, a professor at the University of Utah and expert on traumatic brain injury.
"Oftentimes, athletes want to keep playing. They don't want to benched or on the sidelines, so they're more likely to say they're OK," Bryan said. "This would be able to at least provide some sort of indication if there's a certain threshold of force ... [to ask] do we need to sideline them anyway?"
Though direct hits to the head can lead to concussions, so can body blows, Bryan said.
A player can "still get a bobble-head effect … the brain slamming into the inside of the skull," he said.
Physical signs of concussions include nausea and vomiting, dizziness, headaches and memory impairment. One low-tech way to asses injury is to ask the player a series of questions or ask them to quickly repeat words, since the ability to create new memories is compromised following a concussion.
Merrell and his colleagues professors David Fullwood, Anton Bowden and undergraduate research assistants Parker Rosquist, Brady Anderson, Adam Bilodeau are also exploring other applications, such as measuring footfall impact in shoes and reconstructing car crashes.