Compliant and Robust Tissue‐Like Hydrogels via Ferric Ion‐Induced of Hierarchical Structure

Abstract

It is a challenge to synthesize materials that possess biological tissue‐like properties: strain‐stiffening, robust yet compliant, sensitive, and water‐rich. Herein, a ferric ion‐induced salting out and coordination cross‐linking strategy is presented to create a hierarchical hydrogel network, including dipole–dipole interactions connected curved chains, acrylonitrile (AN)‐rich clusters, and homogeneous iron‐ligand interactions. The design allows the network to deform stress‐free under small strain by unfolding the curved segments with the elastic deformation of the AN‐rich clusters, and sequentially breaking the dipole–dipole interactions and iron‐ligand interactions from weak to strong ones under large strain. As a result, the hydrogel exhibits tissue‐like mechanical properties: low elastic modulus (0.06 MPa), high strength (1.4 MPa), high toughness (5.1 MJ m−3), intense strain‐stiffening capability (27.5 folds of stiffness enhancement), excellent self‐recovery ability and fatigue resistance. Moreover, the hydrogel exhibits high water content (≈84%), good biocompatibility and multi‐sensory capabilities to strain, pressure and hazardous chemicals stimuli. Therefore, this work offers a novel strategy to prepare hydrogel that can mimic the diverse functions of tissues, thereby expanding advanced applications of hydrogel in soft robotics, wearable devices, and biomedical engineering.

Perspectives on recent advancements in energy harvesting, sensing and bio-medical applications of piezoelectric gels

“…Piezoelectric hydrogels with exceptional structural functionality and highly programmable properties have accelerated the development of sensing devices. 147,267–276 Tian and coworkers recently developed a self-powered motion sensor comprised of PHEMA, graphene oxide (GO), and single-walled carbon nanotubes (SWCNTs). 267 The degree of piezoelectricity and sensing properties of the nanocomposite hydrogel was determined by the surface area of the GO and the high strength of the SWCNTs.…”

Amino acid-induced rapid gelation and mechanical reinforcement of hydrogels with low-hysteresis and self-recoverable and fatigue-resistant properties

“…The conductivity of the PLS-1.0-NaCl x hydrogels was characterized using a Keithyley 2450 SourceMeter (USA) in resistance mode. 28 A strain sensor was fabricated by covering both ends of the PLS-1.0-NaCl 1.6 hydrogel with copper foil tape. The sensing properties were investigated using a combination of the Instron 3367 testing machine and Keithyley 2450 Source-Meter.…”

Skin-Inspired Patterned Hydrogel with Strain-Stiffening Capability for Strain Sensors

“…The parameters of strain stiffening include the initial true modulus (E true0 ) calculated (∂σ true /∂λ; σ true is the true stress, and λ is the deformation ratio) at λ → 1, the final true modulus (E true1 ) calculated at the before failure, and the strain-stiffening capability (K) defined by K = E true1 /E true0 . 35,36 Finite Element Simulation. All simulations were performed with COMSOL software.…”