Colour-changing crystal could forecast bomb trauma

2019-03-02 02:04:06

By Tamsin Osborne A sticker for soldiers’ uniforms that changes colour to indicate the strength of a bomb blast could help doctors detect the subtle but long-lasting brain injuries affecting many troops returning from Afghanistan and Iraq. As many as 15% of soldiers returning from those countries are affected by blast traumatic brain injury (bTBI), suffering loss of consciousness or memory caused by shock waves from large roadside bombs. Blast waves stretch and shear the brain, damaging the long nerve cells connecting different regions of the brain. These cells can be several centimetres long, but the damage can only be detected using a specialised MRI scan. The long-term effects of bTBI are uncertain, but evidence suggests that lasting psychological and cognitive problems can result. So a way to record the strength of the blast a person receives would help doctors to decide which patients need special attention. Electronic sensors like accelerometers or pressure transducers are impractical in combat because they need dedicated power supplies. A lightweight, durable crystal that indicates the strength of a blast by changing colour offers a better solution, say researchers. Developed by a team at the University of Pennsylvania in Philadelphia, the photonic crystal’s colour is produced by the way its structure refracts light. A shockwave from a bomb changes that structure, producing visible colour changes. “Depending on the damage, you’ll have different colour intensities,” says Shu Yang, who helped develop the crystal. “Based on that information we can extract how much force the soldier has received.” Yang and colleagues have designed a sticker containing six layers of crystal, each 1 micrometer thick, that can be worn on a soldier’s clothing or helmet. Neurologist David Sharp of Imperial College London, UK, who studies blast traumatic brain injury, told New Scientist that the sticker could provide a way to screen soldiers at risk of low-level brain damage. “Anybody who had a reading over a certain level would have a neuropsycholgical assessment,” he says. They could also receive the specialised diffusion tensor brain scan needed to detect the subtle damage from blast waves. The next step in developing the photonic crystal device will be working out exactly how to quantify the degree of colour change and translate this into a useful measure of neurological damage. The blast-measuring sticker was presented at last week’s 26th Annual National Neurotrauma Symposium in Orlando, Florida. The Human Brain – With one hundred billion nerve cells,