As a new class of materials, implantable flexible electrical conductors have recently been developed and applied to bioelectronics. An ideal electrical conductor requires high conductivity, tissue‐like mechanical properties, low toxicity, reliable adhesion to biological tissues, and the ability to maintain its shape in wet physiological environments. Despite significant advances, electrical conductors that satisfy all these requirements are insufficient. Herein, a facile method for manufacturing a new conductive hydrogels through the simultaneous exfoliation of graphite and polymerization of zwitterionic monomers triggered by microwave irradiation is introduced. The mechanical properties of the obtained conductive hydrogel are similar to those of living tissue, which is ideal as a bionic adhesive for minimizing contact damage due to mechanical mismatches between hard electronics and soft tissues. Furthermore, it exhibits excellent adhesion performance, electrical conductivity, non‐swelling, and high conformability in water. Excellent biocompatibility of the hydrogel is confirmed through a cytotoxicity test using C2C12 cells, a biocompatibility test on rat tissues, and their histological analysis. The hydrogel is then implanted into the sciatic nerve of a rat and neuromodulation is demonstrated through low‐current electrical stimulation. This hydrogel demonstrates a tissue‐like extraneuronal electrode, which possesses high conformability to improve the tissue–electronics interfaces, promising next‐generation bioelectronics applications.

Hydrogel actuators, that convert external energy, such as pH, light, heat, magnetic field, and ion strength, into mechanical motion, have been utilized in sensors, artificial muscles, and soft robotics. For a practicality of the hydrogel actuators in a wide range of fields, an establishment of robust mechanical properties and rapid response are required. Several solutions have been proposed, for example, setting porous and anisotropy structures to hydrogels with nanocomposite materials to improve the response speed and deformation efficiency. In this review paper, we focused on hydrogel actuators including various nanocomposite by categorizing the dimensional aspects of additive materials. Moreover, we described the role of diverse additive materials in terms of the improvement of mechanical property and deformation efficiency of the hydrogel actuators. We assumed that this review will provide a beneficial guidance for strategies of developing nanocomposite hydrogel actuators and outlooks for the future research directions.

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While incorporation of nanoparticles in a polymer matrix generally enhances the physical properties, effective control of the nanoparticle/polymer interface is often challenging. Here, we report a dramatic enhancement of the mechanical properties of polymer nanocomposites (PNCs) using a simple physical grafting method. The PNC consists of low molecular weight poly(ethylene glycol) (PEG) and silica nanoparticles whose surfaces are modified with dopaminemodified PEG (DOPA-mPEG) brush polymers. With DOPA-mPEG grafting, the nanoparticle surface can be readily altered, and the shear modulus of the PNC is increased by a factor of 10 5 at an appropriate surface grafting density. The detailed microstructure and mechanical properties are examined with small-angle X-ray scattering (SAXS) and oscillatory rheometry experiments. The attractive interactions between particles induced by DOPA-mPEG grafting dramatically improve the mechanical properties of PNCs even in an unentangled polymer matrix, which shows a much higher shear modulus than that of a highly entangled polymer matrix.

High-capacity anode materials are promising candidates for increasing the energy density of lithium (Li)-ion batteries due to their high theoretical capacities. However, a rapid capacity fading due to the huge volume changes during charge-discharge cycles limits practical applications. Herein, a layering-charged polymeric binder is introduced that can effectively integrate high-capacity anodes using a strong yet reversible Coulomb interaction and enriched hydrogen bonding. The charged polymeric binder builds a dynamically charge-directed network on the active materials with high versatility and efficiently dissipates the electrode stress with its excellent mechanical properties. In addition, poly(ethylene glycol) (PEG) moieties of the charged binder offer a fast Li-ion conduction pathway that can form an ultra-thick silicon oxide (SiO x )-based electrode (≈10.2 mAh cm −2 ) without compromising the reversible specific capacity and promote effective charge interaction as a mechanical modulator. Such an unprecedented charge-directed binder provides insights into the rational design of a binder for high-capacity anodes.