Biomechanical properties of high-toughness double network hydrogels

This study evaluated the wear property of four novel double-network (DN) hydrogels, which was composed of two kinds of hydrophilic polymers, using pin-on-flat wear testing. The gels involve PAMPS–PAAm gel which consists of poly(2-acrylamide-2-metyl-propane sulfonic acid) and polyacrylamide, PAMPS–PDAAAm gel which consists of poly(2-acrylamide-2-metyl-propane sulfonic acid) and poly(N,N′-dimetyl acrylamide), Cellulose/PDMAAm gel which consists of bacterial Cellulose and poly dimetyl-acrylamide, and Cellulose–Gelatin gel which consists of bacterial Cellulose and Gelatin. Ultra-high molecular weight polyethylene (UHMWPE) was used as a control of a clinically available material. Using a reciprocating apparatus, 106 cycles of friction between a flat specimen and ceramic pin were repeated in water under a contact pressure of 0.1 MPa. To determine the depth and the roughness of the concave lesion created by wear, a confocal laser microscope was used. As a result, the maximum wear depth of the PAMPS–PDMAAm gel (3.20 μm) was minimal in the five materials, while there was no significant difference compared to UHMWPE. There were significant differences between UHMWPE and one of the other three gels. The PAMPS–PAAm gel (9.50 μm), the Cellulose–PDMAAm gel (7.80 μm), and the Cellulose–Gelatin gel (1302.40 μm). This study demonstrated that the PAMPS–PDMAAm DN gel has an amazing wear property as a hydrogel that is comparable to the UHMWPE. In addition, the PAMPS–PAAm and Cellulose–PDMAAm DN gels are also resistant to wear to greater degrees than conventionally reported hydrogels. On the other hand, this study showed that the Cellulose–Gelatin DN gel was not resistant to wear.