Materials Characterization of Cranial Simulants for Blast-Induced Traumatic Brain Injury

Introduction The mechanical response of brain tissue to high-speed forces in the blast and blunt traumatic brain injury is poorly understood. Object-to-object variation and interspecies differences are current limitations in animal and cadaver studies conducted to study damage mechanisms. Biofidelic and transparent tissue simulants allow the use of high-speed optical diagnostics during a blast event, making it possible to observe deformations and damage patterns for comparison to observed injuries seen post-mortem in traumatic brain injury victims. Methods Material properties of several tissue simulants were quantified using standard mechanical characterization techniques, that is, shear rheometric, tensile, and compressive testing. Results Polyacrylamide simulants exhibited the best optical and mechanical property matching with the fewest trade-offs in the design of a cranial test object. Polyacrylamide gels yielded densities of similar to 1.04 g/cc and shear moduli ranging 1.3-14.55 kPa, allowing gray and white matter simulant tuning to a 30-35% difference in shear for biofidelity. Conclusions These materials are intended for use as layered cranial phantoms in a shock tube and open field blasts, with focus on observing phenomena occurring at the interfaces of adjacent tissue simulant types or material-fluid boundaries. Mechanistic findings from these studies may be used to inform the design of protective gear to mitigate blast injuries.