Natural hydrogel in American lobster: A soft armor with high toughness and strength

Abstract

The Homarus americanus, known as American lobster, is fully covered by its exoskeleton composed of rigid cuticles and soft membranes. These soft membranes mainly locate at the joints and abdomen to connect the rigid cuticles, and greatly contribute to the agility of the lobster in swimming and preying. Here we show that the soft membrane from American lobster is a natural hydrogel (90% water) with exceptionally high toughness (14.02 MJ/m 3 ) and strength (17.91 MPa), and is very insensitive to cracks. By combining experimental measurements and large-scale computational modeling, we demonstrate that the unique multilayered structure in this membrane, achieved through the ordered arrangement of chitin fibers, plays a crucial role in dissipating energy during rupture, and making this membrane tough and damage-tolerant. The knowledge learned from the soft membrane of natural lobsters sheds light on designing synthetic soft, yet strong and tough materials for reliable usage under extreme mechanical conditions, including a flexible armor that can provide the full body protection without sacrificing limb mobility.

Nonlinear elasticity of biological basement membrane revealed by rapid inflation and deflation

“…Furthermore, our in situ measurement reveals marked nonlinear elasticity of the BMs whose onset is below 10% of strain. This behavior is in direct contrast to the large linear elastic regime observed in reconstituted Matrigel (24,25) yet is consistent with a wide variety of biological tissues and biopolymer networks (26,40,41). This nonlinear stiffening behavior of the BM may have an important role in maintaining tissue mechanical integrity during growth and deformation (e.g., to avoid structural instability), which is a classical behavior leading to drastic expansion or even rupture when inflating most elastomeric balloons.…”

Arapaima Fish Scale: One of the Toughest Flexible Biological Materials

“…2 The same applies to biological materials that are subjected to extreme loads. [3][4][5][6][7][8][9] The dermal armor of fish is a splendid example where the toughness is essential. [10][11][12][13][14][15][16][17] Arapaima gigas are a large Amazonian fish (weighing up to 150 kgf) living primarily in seasonal lakes infested with ferocious piranhas.…”

Discontinuous fibrous Bouligand architecture enabling formidable fracture resistance with crack orientation insensitivity

“…Varying the arrangements can create materials with vastly different macroscale mechanical properties (1,2,6,7). One prime example is the Bouligand architecture characterized by the stacking of fibrous layers rotated by a pitch angle in chitin nanofibrils-based natural materials (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), such as the exoskeleton of arthropods (e.g., crab, lobster, beetles, and shrimp) and mammal bone, etc. The dactyl club of mantis shrimp composed of mineralized chitin nanofibrils lamellae organized in a twisted plywood (Bouligand) structure exhibits exceptional damage resistance (9,11,16,17).…”