Philadelphia, PA--Researchers at the University of Pennsylvania have developed a nanostructured 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. The findings are described in the ahead-of-print online issue of NeuroImage.
The badge surface consists of nanoscale pores and columns with a wavelength-selective reflectance; the 3-D photonic structures are fabricated using holographic lithography. "We came up the idea of using three-dimensional photonic crystals as a blast-injury dosimeter because of their unique structure-dependent mechanical response and colorful display," said Shu Yang, one of the researchers. Her lab made the materials and characterized the structures before and after the blast to understand the color-change mechanism.
Collapsing columns
Although very 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, changing the material's reflective properties and outward color. The extent of the color change corresponds with blast intensity.
The blast-sensitive material is added as a thin film on small round badges (about the size of "fill-in-the-blank" circles on a multiple-choice test) that could be sewn onto a soldier's uniform. In addition to its use as a blast sensor for brain injury, other applications include testing blast protection of structures, vehicles, and equipment for military and civilian use.
Future studies aim to calibrate the color change to the intensity of exposure to provide an immediate read on the potential harm to the brain and the subsequent need for medical intervention.
The research was funded by the Philadelphia Institute of Nanotechnology and supported in part by the Office of Naval Research and the Air Force Office of Scientific Research.
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