Underwater adhesion plays an essential role in soft electronics for the underwater interface. Although hydrogel-based electronics are of great interest, because of their versatility, water molecules prevent hydrogels from adhering to substrates, thus bottlenecking further applications. Herein, inspired by the barnacle proteins, MXene/PHMP hydrogels with strong repeatable underwater adhesion are developed through the random copolymerization of 2-phenoxyethyl acrylate, 2-methoxyethyl acrylate, and N-(2-hydroxyethyl) acrylamide with the presence of MXene nanosheets. The hydrogels are mechanically tough (elastic modulus of 32 kPa, fracture stress of 0.11 MPa), and 2-phenoxyethyl acrylate (PEA) with aromatic groups endows the hydrogel with nonswelling property and prevents water molecules from invading the adhesive interface, rendering the hydrogels an outstanding adhesive behavior toward various substrates (including glass, iron, polyethylene terephthalate (PET), porcine). Besides, dynamic physical interactions allow for instant and repeatable underwater adhesion. Furthermore, the MXene/PHMP hydrogels exhibit a high conductivity (0.016 S/m), fast responsiveness, and superior sensitivity as a strain sensor (gauge factor = 7.17 at 200%–500% strain) and pressure sensor (0.63 kPa–1 at 0–70 kPa). The underwater applications of bionic hydrogel-based sensors have been demonstrated, such as human motion, pressure sensing, and holding objects. It is anticipated that the instant and repeatable underwater adhesive hydrogel-based sensors extend the underwater applications of hydrogel electronics.

Currently, although conducting polymers have exhibited potential electrophysiological modulation, designing bioinspired ultra‐histocompatible conducting polymers remains a long‐standing challenge. Moreover, the water dispersibility, conductivity, and biocompatibility of conducting polymers are incompatible, which restricts their application in tissue engineering. Herein, a multilevel template dispersion strategy is presented to produce poly(3,4‐ethylenedioxythiophene):(dextran sulfate/carboxymethyl chitosan) (PEDOT:(DSS/CMCS)) with biocompatibility superior to that of commercial poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) without sacrificing processability and conductivity. The PEDOT:(DSS/CMCS) and oxidized dextran solutions form an injectable PEDOT‐based hydrogel (PDCOH) mediated by dynamic covalent imine bonds under mild conditions. The PDCOH has a tissue‐matched modulus and conductivity to adapt to the mechanical environment of dynamic tissue and modulate fibrosis‐induced electrical decoupling. The PDCOH combined with adipose‐derived stem cells demonstrates superior cardiac repair effects over cell suspensions and nonconductive hydrogels, inhibiting ventricular remodeling, reducing fibrous scarring, promoting vascular regeneration, and restoring electrophysiological and pulsatile functions.

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Boron nitride nanosheets (BNNSs) are widely used as fillers to increase the thermal conductivity of a substrate. However, the solvent resistance of BNNSs limits their widespread application. In this paper, hydroxyl functionalized boron nitride nanosheets (OH-BNNSs) were prepared through a one-step aqueous shear exfoliation process. The dangling bonds were formed during the exfoliation process and were attacked by water molecules, and thereby hydroxyl functionalization of BNNSs was achieved. The OH-BNNSs were added to poly(vinyl alcohol) (PVA) to prepare a nanocomposite with high thermal conductivity. The highspeed dispersive homogenizer was selected as the shear-exfoliating device, water as solvent, and sodium dodecyl sulfate (SDS) as surfactant. The effects of operating conditions on the concentration of few-layer OH-BNNSs were systematically studied. Under the optimized conditions, 0.88 mg/mL of OH-BNNSs was obtained. The as-obtained OH-BNNSs were filled in PVA to obtain composite film. The in-plane thermal diffusivity of OH-BNNSs-PVA films reached 9.03 mm 2 /s, which was 40-times the in-plane thermal diffusivity of the pure PVA film and 1.6-times the in-plane thermal diffusivity of the PVA composites filled by BNNSs prepared from ultrasonic exfoliation. The reasons were attributed to better dispersibility in PVA aqueous solution for OH-BNNSs. This paper provided a simple, scalable, and environmentally friendly preparation method for OH-BNNSs.

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