Bioinspired flexible, high-strength, and versatile hydrogel with the fiberboard-and-mortar hierarchically ordered structure

Abstract

The synthetic hydrogels with high water contents are promising for various applications, however, they usually exhibit low mechanical properties. In this work, inspired by the natural biological soft tissues, whose hierarchically ordered fibrous structures result in high strength and good flexibility, a flexible, high-strength, and versatile hydrogel with the fiberboard-and-mortar hierarchically ordered structure (HFMOS) is developed based on ultralong hydroxyapatite (HAP) nanowires and polyacrylic acid (PAA). The as-prepared HFMOS hydrogel has a high water content (~ 70 wt.%), dense structure, and excellent mechanical properties, and these properties are similar to those of the human cartilage and are superior to many hydrogels reported in the literature. The excellent mechanical properties of the HFMOS hydrogel originate from the combination of the fiberboard-and-mortar hierarchically ordered structure, reinforcement of ultralong HAP nanowires, strong interfacial strength, and multiple energy dissipation pathways. Moreover, thanks to the controllable components and injection procedure, the HFMOS hydrogel with a Janus structure is prepared for particular applications. The HFMOS hydrogel possesses abundant ordered water channels, and can be used for loading, release, and directed delivery of various functional substances. Thus, the as-prepared flexible, high-strength, and versatile HFMOS hydrogel possesses a great potential for various applications such as water purification, pollution treatment, biomedicine, nanofluidic devices, and high-performance structural materials.

Recent Advances in Design Strategies of Tough Hydrogels

“…Inspired by natural soft tissues, Yu and Zhu [ 136 ] developed a mechanically enhanced multifunctional hydrogel using highly ordered ultra‐long hydroxyapatite (HAP) nanowires and PAA. While retaining high water content (≈70 wt%), the prepared hydrogel possessed superior mechanical properties (tensile strength of 9.33 MPa and Young's modulus of 277 MPa), higher than that of many reported HAP‐reinforced hydrogels.…”

“…1D NC hydrogels Lu et al [ 135] PAAM-silica nanofiber 1400 -300 -Yu and Zhu [ 136] PAA-HAP nanowire --9330 -Lin et al [ 137] AuNR-PNIPAM 3400 -4.5 -2D NC hydrogels Pereira et al [ 139] PHEMA/GO 200 -1140 6500…”

Effect of Hydrophobic Side Group on Structural Heterogeneities and Mechanical Performance of Gelatin-Based Hydrogen-Bonded Hydrogel

“…The development of tough hydrogels, such as double-network (DN) hydrogels, − slide-ring hydrogels, − nanocomposite hydrogels, − ionic conductive hydrogels, − hydrogen-bonded hydrogels, − and hybrid hydrogels, − has significantly broadened the application potential of hydrogels as biomedical and engineering materials. A tough hydrogel with hydrogen bonds as sacrificial bonds is one of the most promising materials for biomedical and industrial applications due to the widely distributed bond strength and insensitivity to the neutral ionic environment of hydrogen bonds.…”

Microwave-Assisted Hydrothermal Rapid Synthesis of Ultralong Hydroxyapatite Nanowires Using Adenosine 5′-Triphosphate

“…On the other hand, ultralong HAP nanowires, from the structural standpoint, have advantages of high flexibility, high toughness and high strength, and can be interwoven into a high-strength porous networked structure [ 22 , 23 ]. Generally, the higher aspect ratios of HAP nanowires (with nanoscale diameters and larger lengths) can greatly enhance their properties and thus promote their diverse applications [ 29 , 30 ].…”