In the multiple conflicts ongoing since 2001, there has been a dramatic rise in Traumatic Brain Injuries (TBI) due to the close proximity our soldiers face with explosions, bombs, and weapons.

TBI has been called the ‘invisible wound of war’ as many times the soldiers suffering from its effects won’t notice the toll for months, even years.

Now the military is testing small, coin-sized sensors that can be used on the battlefield to test members for what is now being termed, multiple, mild traumatic brain injuries or mTBI.

Since 2010, there have been more than 361,000 service members diagnosed with some form of traumatic brain injury, according to the US Defense Department’s Defense and Veterans Brain Injury Center. The three different forms of TBI—severe, moderate, and mild—all manifest in different ways ranging from memory loss and extended unconsciousness to a simple headache. Mild TBI tends to go unnoticed. One blast may not cause effects like memory loss or slurred speech, the telltale signs of brain trauma, and, especially while in theatre, there’s really no easy way to diagnose the condition, says Alex Balbir, director of Warrior Care Network and Independence Services at the Wounded Warriors Project.

“The brain has very interesting ways of responding to these mild traumas,” says Balbir. “It’s only after a few [mTBI’s], that’s when you start to see the effects of the trauma” like memory loss and slurred speech.

In an effort to fill that technology gap, Timothy Bentley, and his team at the Office of Naval Research’s Warfighter Performance Department in Arlington, Virginia, have engineered new sensor technology that could give medics on the battlefield a clearer idea of whether or not an injury actually occurred after a blast.

The coin-sized sensors, placed in service members’ helmets and tactical gear, detect the impact of a blast wave—which moves faster than the speed of sound—and assign it a number, a measure of blast strength. The number is then run through an algorithm that computes how a service member was hit by a blast, which sensors were activated based on their placement, and then tells medics if the service member needs to get off the field immediately or not.

If the algorithm shows a possible mTBI, medics in the field have the service member hold a mouse-sized tool—nicknamed the “brain gauge”—that stimulates the fingertips through eraser-sized vibrators. The brain gauge vibrates each finger for a different length of time—if a service member can’t recognize which vibrations last longer, it’s highly likely he or she has suffered an mTBI.