Conductive polymer hydrogels (CPHs) that combine the unique properties of hydrogels and electronic properties of conductors have shown their great potentials in wearable/implantable electronic devices, where materials with remarkable mechanical properties, high conductivity, and easy processability are demanding. Here, we have developed a new type of polyion complex/polyaniline (PIC/PAni) hybrid hydrogels that are tough, conductive, and can be facilely patterned. The incorporation of conductive phase (PAni) into PIC matrix through phytic acid resulted in hybrid gels with ∼65 wt % water; high conductivity while maintaining the key viscoelasticity of the tough matrix. The gel prepared from 1 M aniline (Ani) exhibited the breaking strain, fracture stress, tensile modulus, and electrical conductivity of 395%, 1.15 MPa, 5.31 MPa, and 0.7 S/m, respectively, superior to the most existing CPHs. The mechanical and electrical performance of PIC/PAni hybrid hydrogels exhibited pronounced rate-dependent and self-recovery behaviors. The hybrid gels can effectively detect subtle human motions as strain sensors. Alternating conductive/nonconductive patterns can be readily achieved by selective Ani polymerization using stencil masks. This facile patterning method based on PIC/PAni gels can be readily scaled up for fast fabrication of wavy gel circuits and multichannel sensor arrays, enabling real-time monitoring of the large-extent and large-area deformations with various sensitivities.

The thermal conductivity of nanocrystalline ceria films grown by unbalanced magnetron sputtering is determined as a function of temperature using laser-based modulated thermoreflectance. The films exhibit significantly reduced conductivity compared with stoichiometric bulk CeO 2 . A variety of microstructure imaging techniques including X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron analysis, and electron energy loss spectroscopy indicate that the thermal conductivity is influenced by grain boundaries, dislocations, and oxygen vacancies. The temperature dependence of the thermal conductivity is analyzed using an analytical solution of the Boltzmann transport equation. The conclusion of this study is that oxygen vacancies pose a smaller impediment to thermal transport when they segregate along grain boundaries. D. Clarke-contributing editor Manuscript No. 32233.

Stiff yet recoverable water-containing materials can be found in many biological tissues including tendons, cartilages, and skins. However, it remains a challenge to develop hydrogels as load-bearing materials where high stiffness and toughness, as well as fast recoverability, are required. Making framework more compact with more rigid chains could make a gel stiffer but also restrict its recovery for lower chain mobility. Here, we report a rigid yet recoverable hydrogel by incorporating polyrotaxane into a physically cross-linked network with movable slide-ring (SR) as the chemically anchoring point. The dynamic and robust carboxyl–Fe3+ coordination bonds endow the gel with high stiffness and potential to recovery, while SR structures within the framework act as pulleys to equalize the distribution of stress and activate the reattachment of dynamic bonds. The obtained gel possesses a tunable Young’s modulus up to 18.3 MPa, comparable to that of natural cartilage. More notably, SR gel exhibits faster recovery than the reference gel with fixed cross-links, as confirmed by analyzing their stress relaxation behaviors using a three-dimensional continuum model. This work provides an innovative and practical strategy for designing rigid yet recoverable hydrogels with high strength and toughness, which can be further applied to other systems containing dynamic bonds.

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A hybrid conductive hydrogel system was facilely integrated with complex circuits. The obtained hydrogel electronics show excellent mechanical and electrical performances, enable monitoring tensile strain, pressure, and temperature.