Hysteresis-Free Nanoparticle-Reinforced Hydrogels.

The elastic storage and release of mechanical energy has been key to many developments throughout the history of mankind. Resilience, absent hysteresis, has been an elusive goal to achieve, particularly at large deformations. Using a low-crosslink density polyacrylamide hydrogel at 96% water content having hyper-branched silica nanoparticles (HBSPs) as the major junction points, we have realized a hysteresis-free material. The fatigue-free characteristic of these composite hydrogels is evidenced by the invariance of the stress-strain curves at strain ratios of 4, even after 5,000 cycles. At a strain ratio of 7, only a 1.3% hysteresis is observed. A markedly increased strain ratio-at-break of 11.5 is observed. The unique attributes of these resilient hydrogels are manifested in the high-fidelity detection of dynamic deformations under cyclic loading over a broad range of frequencies, difficult to achieve with other materials. This article is protected by copyright. All rights reserved.