'Blast badge' allows instant diagnosis of exposure to explosive shock

Posted by Kate Taylor

A new cap badge could allow immediate diagnosis of the severity of exposure to explosive blasts on the battlefield.

Investigators at the University of Pennsylvania have developed a color-changing patch that could be worn on soldiers' helmets and uniforms to indicate the strength of exposure to blasts from explosives in the field.

Blast-induced traumatic brain injury is one of the commonst injuries of the current wars in Iraq and Afghanistan. But with no objective information on relative blast exposure, soldiers with brain injury may not receive appropriate care and can be returned to the battlefield too soon.

The Penn team is working on a calibration system for the badge, to allow the color change to indicate the intensity of exposure, providing an immediate reading on the potential harm to the brain and the subsequent need for medical intervention.

"We wanted to create a 'blast badge' that would be lightweight, durable, power-free, and perhaps most important, could be easily interpreted, even on the battlefield," says Douglas H Smith,  professor of neurosurgery at the university of Pennsylvania.

"Similar to how an opera singer can shatter glass crystal, we chose color-changing crystals that could be designed to break apart when exposed to a blast shockwave, causing a substantial color change."

The badges consist of nanoscale structures whose make-up preferentially reflects certain wavelengths. Lasers sculpt these tiny shapes into a plastic sheet.

"We came up with the idea of using three-dimensional photonic crystals as a blast injury dosimeter because of their unique structure-dependent mechanical response and colorful display,” says Penn's Shu Yang.

Although stable in the presence of heat, cold or physical impact, the nanostructures are selectively altered by blast exposure. The shockwave causes the columns to collapse and the pores to grow larger, thereby changing the material's reflective properties and color.

Other applications include testing blast protection of structures, vehicles and equipment for military and civilian use.