With growing interest in flexible and wearable devices, the demand for nature-inspired soft smart materials, especially intelligent hydrogels with multiple perceptions toward external strain and temperatures to mimic the human skin, is on the rise. However, simultaneous achievement of intelligent hydrogels with skin-compatible performances, including good transparency, appropriate mechanical properties, autonomous self-healing ability, multiple mechanical/ thermoresponsiveness, and retaining flexibility at subzero temperatures, is still challenging and thus limits their application as skinlike devices.Here, conductive nanocomposite hydrogels (NC gels) were delicately designed and prepared via gelation of oligo(ethylene glycol) methacrylate (OEGMA)-based monomers in a glycerol−water cosolvent, where inorganic clay served as the physical cross-linker and provided conductive ions. The resultant NC gels exhibited good conductivity (∼3.32 × 10 −4 S cm −1 , akin to biological muscle tissue) and an autonomously self-healing capacity (healing efficiency reached 84.8%). Additionally, such NC gels displayed excellent flexibility and responded well to multiple strain/temperature external stimuli and subtle human motions in a wide temperature range (from −20 to 45 °C). These distinguished properties would endow such NC gels significant applications in fields of biosensors, human−machine interfaces, and soft robotics.

8231wileyonlinelibrary.com the tumor, many kinds of nanomaterials have been developed for the imaging of tumor, such as magnetic (Fe [2] /Gd [3] /Mn [4] based) nanoparticles for magnetic resonance imaging (MRI), luminescent (such as lanthanide [5] /carbon [6] -based) nanoparticles for fluorescent imaging, and high atomic number or high X-ray attenuation coefficient nanomaterials (iodine [7] /gold [8] / bismuth [9] -based) for X-ray computed tomography (CT) imaging. Furthermore, to cure the tumor, various nanomaterials have also been investigated for developing new therapy methods, including nanocarriers (mesoporous silica, [10] polymer nanocapsules [11] ) for advanced chemotherapy, nanophotosensitizers [12] for the photodynamic therapy and photothermal nanoagents for the ablation of tumor. Among these therapy methods, near-infrared (NIR) laser-induced photothermal ablation therapy (PAT) has drawn much attention as a minimally-invasive and potentially more effective technology. [12b,13] For achieving the NIR-PAT for tumors, several types of photothermal nanoagents have been well researched, containing polymer [14] /metal [15] /carbon [6] / semiconductor [16] -based nanomaterials. Our group has also prepared Cu [16a,17] /W [16b,18] -based semiconductors as novel and efficient photothermal agents. To further enhance the therapy efficiency and minimize side effects from NIR-PAT, the combination of NIR-PAT with bioimaging has been proposed for the simultaneous diagnosis and therapy of tumors, since bioimaging in vivo can be used to guide the design of NIR-PAT plans, for example, by choosing the optical doses and/or optimal irradiation region, and deciding the best timing of laser treatment when the photothermal agent reaches the peaked accumulation in the targeted lesion. [19] For realizing the imaging-guided NIR-PAT, multifunctional nanomaterials, which contain NIR photothermal conversion ability and at least one of bioimaging functions, should be designed and prepared. Currently, three kinds of multifunctional nanomaterials with complex structures have been chiefly developed. The first kind is the mixture containing two or more imaging/therapy agents that are encapsulated/conjugated by organic/polymer molecules, including metal-metal, [3,20] The ideal theranostic nanoplatform for tumors is a single nanoparticle that has a single semiconductor or metal component and contains all multimodel imaging and therapy abilities. The design and preparation of such a nanoparticle remains a serious challenge. Here, with FeS 2 as a model of a semiconductor, the tuning of vacancy concentrations for obtaining "all-in-one" type FeS 2 nanoparticles is reported. FeS 2 nanoparticles with size of ≈30 nm have decreased photoabsorption intensity from the visible to near-infrared (NIR) region, due to a low S vacancy concentration. By tuning their shape/size and then enhancing the S vacancy concentration, the photoabsorption intensity of FeS 2 nanoparticles with size of ≈350 nm (FeS 2 -350) goes up with the increase of the wavelength...

Hydrogels are an important class of soft materials with high water retention that exhibit intelligent and elastic properties and have promising applications in the fields of biomaterials, soft machines, and artificial tissue. However, the low mechanical strength and limited functions of traditional chemically cross-linked hydrogels restrict their further applications. Natural materials that consist of stiff and soft components exhibit high mechanical strength and functionality. Among artificial soft materials, nanocomposite hydrogels are analogous to these natural materials because of the synergistic effects of nanoparticle (NP) polymers in hydrogels construction. In this article, the structural design and properties of nanocomposite hydrogels are summarized. Furthermore, along with the development of nanocomposite hydrogel-based devices, the shaping and potential applications of hydrogel devices in recent years are highlighted. The influence of the interactions between NPs and polymers on the dispersion as well as the structural stability of nanocomposite hydrogels is discussed, and the novel stimuli-responsive properties induced by the synergies between functional NPs and polymeric networks are reviewed. Finally, recent progress in the preparation and applications of nanocomposite hydrogels is highlighted. Interest in this field is growing, and the future and prospects of nanocomposite hydrogels are also reviewed.

The advocacy of smart living results in a high demand for wearable and flexible sensors to monitor human motions. Among these, sensors based on strain−optics conversion are attractive due to their inherent electrical safety and electromagnetic immunity in comparison to strain−electricity conversion sensors. Particularly, hydrogel-based optical fiber sensors are biocompatible, flexible, and stretchable and thus are potentially applicable to health monitoring, human−machine intelligence, and soft robots. Nonetheless, hydrogelbased optical fibers still demonstrate challenges such as limited stretch ratios from chemical cross-linking networks and insufficient light transmittance from dehydration or nucleation of water. Herein, flexible and stretchable strain sensors based on glycerol-introducing nanocomposite hydrogel fibers (GN-Fibers) were achieved via dynamic stretching of a reactive pregel from monomer/nanoparticle hybrid precursors in a glycerol−water cosolvent. The resultant GN-Fibers evolved with anisotropic microstructures, displaying excellent tensile strength (9.76 MPa), high elastic modulus (32.63 MPa), low light propagation attenuation (0.26 dB cm −1 ), and broad strain range. Owing to the use of glycerol−water, such GN-Fibers also exhibited long-term moisture-retaining and antifreezing properties. In addition, GN-Fibers functioned well as sensors based on strain−optics conversion to monitor stretching and compressing behaviors. It is believed that such an optical fiber based strain sensor is a gateway to fabrication of next-generation wearable and flexible devices for health monitoring or artificial intelligence.

This work presented a facile reactive spinning method for generating nanocomposite gel fibers with high anisotropy from monomers/nanoparticle hybrid precursors.