The OBEI Clinic team determined the mechanism of liquid-induced expansion of advanced hemostatic agent (AHA) sponges. The team hypothesized that molecular interaction between water and regenerated cellulose strongly affects expansion. Other contributing factors include temperature, sponge composition, fluid properties, and initial moisture content. The team designed experimental procedures to characterize pore structure, wettability, absorption, material properties, and expansion. Additionally, finite element modeling of the AHA sponges provided insight to internal fluid dynamics and a basis for comparison to experimental results.