Hysteresis‐Free Nanoparticle‐Reinforced Hydrogels

Abstract

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 hyperbranched silica nanoparticles (HBSPs) as the major junction points, a hysteresis‐free material is realized. 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 5000 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.

High‐Stretchability, Ultralow‐Hysteresis ConductingPolymer Hydrogel Strain Sensors for Soft Machines

“…Despite recent advances to enhance the stretchability with the elastomeric matrix, highly stretchable conducting polymer hydrogel strain sensors suffer from the high hysteresis due to the irreversible energy dissipation of viscoelastic elastomers under cyclic stretch. [ 27,28 ] Additionally, current strain sensors are generally susceptible to the interference of off‐axial distortions such as twisting and pressing when operated under unconstrained conditions. [ 29,30 ] These limitations significantly hinder their practical applications in soft robotic systems with a large deformation range and versatile functionalities.…”

Recyclable, Healable, and Tough Ionogels Insensitive to Crack Propagation

“…Addition of nanocomposites improved the toughness and strength of the hydrogels through the interaction between surface functional groups and external polymer matrix (hydrophobic association by amphiphilic triblock copolymer, strong hydrogen bond, and coordination bond). [19,22,[30][31][32][33] The hydrogels need residence time to recover the damaged mechanical properties under cyclic load due to the unstable mechanical properties of reversible bonds.Recyclability and mechanical stability of polymer networks are contradictory properties. The covalently crosslinked rigid network ensures the stability of the polymer framework at the expense of the regeneration and recycling capacity.…”

“…Addition of nanocomposites improved the toughness and strength of the hydrogels through the interaction between surface functional groups and external polymer matrix (hydrophobic association by amphiphilic triblock copolymer, strong hydrogen bond, and coordination bond). [19,22,[30][31][32][33] The hydrogels need residence time to recover the damaged mechanical properties under cyclic load due to the unstable mechanical properties of reversible bonds.…”

Interface interaction-mediated design of tough and conductive MXene-composited polymer hydrogel with high stretchability and low hysteresis for high-performance multiple sensing

“…The hysteresis is approximately 15% based on the calculation from the cycle curve of tensile tests under different strains, indicating a low hysteresis. Moreover, fatigue resistance is needed to maintain cyclic actuation for practical applications [47,48]. Ten successive loading-unloading tests at a strain of 500% were conducted to evaluate the fatigue hysteresis of the MCP hydrogel, as shown in Fig.…”