The wound most characteristic of soldiers who have been deployed to Iraq and Afghanistan is traumatic brain injury (TBI). Sudden attacks from weapons such as improvised explosive devices (IEDs), grenades and roadside bombs have been frequent occurrences during the war and have caused much damage to the brains of soldiers. Many affected by these types of explosions are unaware of the severity of the trauma, and it is possible for TBI to go undiagnosed long after they return home.According to a 2008 Rand Corp. report, 19.5 percent (320,000) of soldiers suffer from TBI, and a partially overlapping population of roughly 18.5 percent experience depression and posttraumatic stress disorder. It’s estimated that only half of soldiers with these disorders seek treatment. The Palo Alto Research Center (PARC), a Xerox company, under the DARPA Sensor Tape Program, has devised a way to record the number and intensity of explosions that soldiers experience by applying a blast dosimeter to their helmets. “The objective of the Sensor Tape Program is to produce an inexpensive, disposable, very lightweight blast dosimeter to measure the phenomenology associated with repeated exposure to blast events,” said Dr. Jennifer Ricklin, program manager for DARPA.Disposable blast dosimeters, printed with electronic sensors, memory processors and thin-film batteries, are intended to record the number and intensity of blasts that a soldier is exposed to during combat. Courtesy of PARC. IEDs emit shock waves that travel 1000 feet per second and cause severe brain damage such as multiple concussions, brain inflammation and blockage of blood flow, with symptoms ranging from headaches and sleeplessness to memory and concentration deficiencies. Knowing the power of these blasts could provide a better understanding of the causes of TBI and allow for earlier diagnosis.Components and capabilitiesThe dosimeters will be flexible plastic strips created by depositing solution-processed materials such as organic semiconductors, polymer dielectrics and metal nanoparticles onto a plastic substrate using ink-jet printing technology, a patterning technique for large-area electronics. Lamination protects the electronic sensors, memory processors and thin-film batteries printed on the strips.They are designed with pressure gauges, acoustic levels, light sensors and thermometers as well as accelerometers to measure the acceleration of explosion forces. Many effects are thought to be attributed to TBI, so the features on this device are necessary for a more precise analysis of accumulated blast exposure.The strip will be applied with an adhesive layer to the soldier’s helmet, where it will be left for a maximum of seven days. After a device reads the data, the week’s information will be added to the soldier’s prior exposure history. “The plan is for the data to be associated with the military member’s medical record, since there is often a time lag between blast exposures and manifestation of symptoms or illnesses,” Ricklin said. If a soldier reaches a high level of exposure, he or she may be marked for a follow-up evaluation.Other advantages are that the strips are very small and inexpensive, with an estimated cost of less than $1 each. A limitation to the dosimeter is that it can store data of up to only 20 blast exposures per week. If a soldier experiences more than 20 blasts, the strip will replace the weakest explosion with the new, stronger exposure. Or, if it is lower than the weakest blast, it will not be recorded at all.DARPA has awarded PARC a $5 million contract for up to three years to develop and test the strips for military use. According to Ricklin, the program is expected to produce 25 prototypes for field testing by the spring of 2009; by 2010, 1000 prototypes should be available. Under a Small Business Innovation Research program, PARC is working with another company to integrate this technology into a helmet using standard silicon technology.