Design of stiff, tough and stretchy hydrogel composites via nanoscale hybrid crosslinking and macroscale fiber reinforcement

Abstract

Hydrogels' applications are usually limited by their weak mechanical properties. Despite recent great progress in developing tough hydrogels, it is still challenging to achieve high values of , toughness and modulus all together in synthetic hydrogels. In this paper, we designed highly stretchable, tough, yet stiff hydrogel composites via a combination of nanoscale hybrid crosslinking and macroscale fiber reinforcement. The hydrogel composites were constructed by impregnating a 3D-printed thermoplastic-fiber mesh with a tough hydrogel crosslinked both covalently and ionically. The hydrogel composites can achieve a fracture energy of over 30,000 J m(-2), a modulus of over 6 MPa, and can be stretched over 2.8 times even in the presence of large structural defects. The enhancement of toughness in the new hydrogel composites relies on multiple pairs of toughening mechanisms which span over multiple length scales. A theoretical model is further developed to predict the toughness and modulus of the hydrogel composites and guide the design of future materials.

Three-Dimensional Printing Fiber Reinforced Hydrogel Composites

“…First the fibre scaffold was printed and the composite structure is completed by immersing the scaffold into a hydrogel precursor solution and polymerizing the gel around the fibres. [16][17] These studies and others involving hydrogels reinforced with fibres, 18 and woven textiles [19][20] have demonstrated an increase in modulus and strength. Indeed, many soft tissues can be thought of as fibre reinforced hydrogel composites.…”

Energy‐Dissipative Matrices Enable Synergistic Toughening in Fiber Reinforced Soft Composites

“…Based on this concept, some attempts have been made to fabricate fiber reinforced hydrogel composites. [24][25][26][27][28][29] Utilizing this technique, researchers have been able to increase and tune the stiffness and toughness achievable with hydrogel-based systems. However, developing soft composites with synergistically improved mechanical properties, such as those seen in hard bioinspired composites, is still a challenge.…”

Fiber-reinforced tough hydrogels

“…Many attempts have been made to improve the toughness of hydrogels [13,[15][16][17][18]. Doublenetwork hydrogels were the first class of hydrogels to exhibit significant fracture toughness, with fracture energies in the range of 100-1000 Jm -2 [15].…”

“…It contains more than 70% water, but is remarkably stiff and tough [7,8]. It comes as no surprise, then, that hydrogelbased composites are being actively explored for use as synthetic tissues and in biocompatible products [9][10][11][12][13][14][15][16].…”