“…Load-bearing biocomposites are typically structured as arrays of rigid and predominantly elastic reinforcing elements (e.g., biominerals or crystalline biopolymers), which are connected by a more compliant and energy-dissipating matrix material (e.g., proteins or hemicellulose) through submicron length, compositionally graded, and irregularly-shaped interfacial regions [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. The effective dynamic (viscoelastic) modulus of these interfacial regions provides the biocomposites’ diverse mechanical functions, including adsorbing impacts, detaining cracks, and filtering mechanical signals [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Identifying the interfacial dynamic modulus of biocomposites is a long-standing objective of biomaterial science research [ 18 ], it is considered the keystone toward understanding the fundamental structure–function relationships in various biocomposite systems [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”