MEAM Seminar: “Programmable Strain-responsive Biopolymer Networks Adapt to High Magnitudes of Mechanical Loading”

Biopolymer hydrogel materials typically exhibit relatively low range of programmable modulus less than 100 kPa, which limits their biomedical applications, such as in articular cartilage and synthetic joints, where tissues are cyclically loaded with high magnitudes of peak stress on the order of 10MPa, and applications in soft robotics require moduli across orders of magnitude from 1 kPa to 100 MPa. Here, we achieved a wide range of mechanical properties with double network biopolymer hydrogels that can sustain over 10-100 MPa peak stress under repeated axial unconfined compression. Previous systems use double-network to enhance hydrogel’s toughness and strength. Here, cryogelation generates a foam network that undergoes a rarefied to densified phase transition, which is reinforced with a second dissipative network to yield highly tunable properties across orders of magnitude of applied stress. The foam network is formed by cryogelation of a covalently crosslinked collagen-glutaraldehyde (GA) biopolymer network that can sustain repeated loading through phase transition of its porous foam structure. Interpenetrating ionically-crosslinked alginate biopolymers tune the final modulus to make the hydrogel programmable in a high range of mechanical performance. This dual-network composite hydrogel system also exhibits reversible properties, achieved by chelating ions to reduce ionic crosslinks or restoring crosslinks by supplying additional ions. Together, these data demonstrate a robust hydrogel composite system adaptable to wide ranges of mechanical loading.