Biological materials have the ability to withstand extreme mechanical forces due to their unique multilevel hierarchical structure. Here, we fabricated a nacre-mimetic nanocomposite comprised of silk fibroin and graphene oxide that exhibits hybridized dynamic responses arising from alternating high-contrast mechanical properties of the components at the nanoscale. Dynamic mechanical behavior of these nanocomposites is assessed through a microscale ballistic characterization using a 7.6 μm diameter silica sphere moving at a speed of approximately 400 m/s. The volume fraction of graphene oxide in these composites is systematically varied from 0 to 32 vol % to quantify the dynamic effects correlating with the structural morphologies of the graphene oxide flakes. Specific penetration energy of the films rapidly increases as the distribution of graphene oxide flakes evolves from noninteracting, isolated sheets to a partially overlapping continuous sheet. The specific penetration energy of the nanocomposite at the highest graphene oxide content tested here is found to be significantly higher than that of Kevlar fabrics and close to that of pure multilayer graphene. This study evidently demonstrates that the morphologies of nanoscale constituents and their interactions are critical to realize scalable high-performance nanocomposites using typical nanomaterial constituents having finite dimensions.

Cavitation is the sudden, unstable expansion of a void or bubble within a liquid or solid subjected to a negative hydrostatic stress. Cavitation rheology is a field emerging from the development of a suite of materials characterization, damage quantification, and therapeutic techniques that exploit the physical principles of cavitation. Cavitation rheology is inherently complex and broad in scope with wide-ranging applications in the biology, chemistry, materials, and mechanics communities. This perspective aims to drive collaboration among these communities and guide discussion by defining a common core of highpriority goals while highlighting emerging opportunities in the field of cavitation rheology. A brief overview of the mechanics and dynamics of cavitation in soft matter is presented. This overview is followed by a discussion of the overarching goals of cavitation rheology and an overview of common experimental techniques. The larger unmet needs and challenges of cavitation in soft matter are then presented alongside specific opportunities for researchers from different disciplines to contribute to the field. soft solids | traumatic brain injury | TBI | rheology | bubble Cavitation is the sudden, unstable expansion of a void or bubble within a liquid or solid subjected to a negative hydrostatic stress. While predominantly studied in fluids, cavitation is also an origin of damage in soft materials, including biological tissues. Examples of cavitation in fluids and soft solids are shown in Fig. 1 A-C. As one key example, strong evidence suggests that cavitation occurs in the brain during sudden impacts, leading to traumatic brain injury (TBI) (3). Research on this life-impacting injury and its relation to cavitation has accelerated in recent years (4-8). A broader and deeper understanding of cavitation within soft matter is necessary to navigate the complex paths that lead to damage in the brain and other soft materials. Cavitation in fluids has been studied extensively since Rayleigh's (9) formulation in 1917, which predicted that the maximum pressure in a cavitating liquid is proportional to the far-field pressure and inversely proportional to the cavity size. As surface energy

Characterizing the high-strain-rate and high-strain mechanics of soft materials is critical to understanding the complex behavior of polymers and various dynamic injury mechanisms, including traumatic brain injury. However, their dynamic...

Periodic bimetallic microstructures using nickel and gold are fabricated on an elastomeric substrate by use of strain‐induced buckling of the metallic layers, which can be compatible with roll‐to‐roll manufacturing. The intrinsically low emissivity of gold in the midinfrared regime is selectively enhanced by the surface plasmonic resonance at three different midinfrared wavelengths, 4.5, 6.3, and 9.4 µm, respectively, which directly correspond to the structural periodicities of the metallic microstructures. As the thermal emission enhancement effect exists only for the polarization perpendicular to the orientation of the microstructures, substantially polarized thermal emission with an extinction ratio close to 3 is demonstrated. Moreover, the elastically deformed plasmonic thermal emitters demonstrate strain‐dependent emission peaks, which can be applied for future mechano–thermal sensing and dynamic thermal signature modulation.

Metallic photonic crystals (MPCs) exhibit wavelength-selective thermal emission enhancements and are promising thermal optical devices for various applications. Here, we report a scalable fabrication strategy for MPCs suitable for high-temperature applications. Well-defined double-layer titanium dioxide (TiO) woodpile structures are fabricated using a layer-by-layer soft-imprint method with TiO nanoparticle ink dispersions, and the structures are subsequently coated with high purity, conformal gold films via reactive deposition from supercritical carbon dioxide. The resulting gold-coated woodpile structures are effective MPCs and exhibit emissivity enhancements at a selective wavelength. Gold coatings deposited using a cold-wall reactor are found to be smoother and result in a greater thermal emission enhancement compared to those deposited using a hot-wall reactor.