Adaptive liquid flow behavior in 3D nanopores.

Liquid flow speed in 2D nanochannel models has previously been characterized, whereas liquid flow behavior in 3D nanostructured materials remains unknown. To fill this gap, we have developed a novel liquid nanofoam (LN) system composed of nanoporous silica gel particles and a non-wettable liquid phase. We demonstrated that the dynamic behavior of the LN sample was strain rate insensitive by impacting it with a drop weight at various incident speeds. Using this experimental setup, we measured the effective liquid flow speed in 3D nanopores and showed that it was 5 orders of magnitude higher than that of quasi-static loading. Importantly, the liquid infiltration speed as well as the energy absorption efficiency of the LN was found to be adaptive to the incident speed and energy level. This provides a mechanistic explanation for the high energy absorption efficiency of LNs at high blast impact levels and strain rates, and demonstrates the importance of experimentally investigating the liquid flow behavior in 3D instead of the traditional 2D nanopores.