Investigators at the University of Pennsylvania School of Medicine and School of Engineering and Applied Sciences in Philadelphia have developed a color-changing patch that could be worn by military service members to indicate the strength of exposure to blasts from explosives in the field. The findings are described in the online edition of the journal NeuroImage (paid subscription required).
The badges are made of nanoscale structures, in this case pores and columns, whose preferred composition reflects certain wavelengths. (1 nanometer = 1 billionth of a meter.) Lasers then sculpt these tiny shapes into a plastic sheet. Senior author Douglas Smith, professor of neurosurgery at Penn, describes the structures as looking “like layers of Swiss cheese with columns in between.”
Although very stable in the presence of heat, cold, or physical impact, the nanostructures are selectively altered by blast exposure. The shock wave from the blast causes the columns to collapse and the pores to grow larger, thereby changing the material’s reflective properties and outward color. The material is designed so that the extent of the color change corresponds with blast intensity. The blast-sensitive material is added as a thin film on small round badges that can be worn on a service member’s battle gear to indicate the extent of his or her blast exposure.
American and NATO troops in Afghanistan, as well as civilian support staff, run a high risk of blast injuries, particularly traumatic brain injury (TBI) from explosions. According to the the Defense and Veterans Brain Injury Center, and based on Department of Defense statistics, more than 188,000 service members suffer from TBI.
Because TBI can occur in conjunction with more direct, life-threatening wounds, the condition is not always immediately diagnosed. The dosimeter developed by Smith and colleagues can provide an indicator of blast exposure in these circumstances, as well as serve as a day-to-day sensor of accumulated blast exposure. 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.
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