The low melting gallium‐based liquid metal (LM) is showing tremendous potential in many technologies due to its unique properties. However, the high surface tensions as well as oxidations result in poor wetting capability on most solid surfaces, which limits its practical application. In this work, a simple chemical method is utilized to enable spontaneous wetting of LM on various metal surfaces, such as copper, nickel, and iron. It is found that LM can spread rapidly on the metal substrates treated with CuCl2 solution through reactive‐wetting and metallic bond‐enabled wetting mechanism. The redox reaction between Ga and copper compound and the formation of intermetallic compound via LM phagocytosis help drive LM to wet metal substrates spontaneously. Many factors affecting the wetting behaviors of LM, including surface roughness, crystal size, and ambient environment, are systematically studied. This finding provides a novel strategy to solve the wetting problem of LM and will enable wider applications.

As an important 2D nanomaterial, boron nitride nanosheet (BNNS) has aroused much academic interest due to its high in‐plane thermal conductivity (TC) and good electrical insulation capability. However, the brittleness and low strength of high‐content BNNS films greatly limit its practical application. In the authors’ work, densely layered films containing 2D exfoliated graphene fluoride sheets (GFS) and BNNS with similar phonon vibrational characteristics and intrinsic high TC, are fabricated via vacuum‐assisted filtration (VAF) using cellulose nanofiber (CNF) as the framework. The strong hydrogen bonding between the ternary components and tight “face‐to‐face” contact between the BNNS/GFS interfaces significantly improve the thermal pathway density. Superior in‐plane TC (55.65 W m−1 K−1) of the nanocomposite can be achieved at the 90 wt% BNNS‐GFS loading, a value of 114% greater than a BNNS/CNF counterpart. Additionally, the as‐prepared papery films show tolerance to bending, folding, humid environment, and high‐temperature flame. The newly developed hybrid films are promising for efficient thermal management applications in many electronic devices.

For example, in the Ga/Cu-10Ni system, the reaction between Cu and Ni with Ga produces CuGa 2 and Ga 5 Ni IMCs, respectively, which results in the gradual solidification of the composites. [23] Besides, the solidification was reported to be accelerated at an elevated ambient temperature. Liu et al. suggested the unambiguous existence of Ga 4 Ni 3 and InNi 3 in EGaIn-Ni composite system that was treated at 80 °C for 4 h. [24] Hence, it is necessary to form shielding layer on magnetic particles to achieve long-term fluidity as well as magnetism.Herein, core-shell structural Ni@ SiO 2 nanoparticles were prepared by the hydrolysis method using sodium metasilicate, and a recoverable magnetic galinstan-Ni@SiO 2 (called GNS) composite with high stability was developed by mixing galinstan with Ni@ SiO 2 nanoparticles. The silica shell on the surface of Ni@SiO 2 nanoparticles suppresses the alloying reaction between Ni and galinstan. Meanwhile, the GNS pastes hold stable rheological and magnetic properties without changing the specific saturation magnetization over time. In addition, the flowable GNS composite is driven under magnetic field to achieve self-healing where mechanical damage occurs in circuits (R/R 0 < 1.06 after five scratching cycles). Results and Discussion Preparation of the GNS PastesThe fabrication process of the magnetic GNS pastes is schematically illustrated in Figure 1, which includes the preparation process of Ni@SiO 2 nanoparticles by the hydrolysis coprecipitation method (Figure 1a) as well as the blending process for GNS pastes (Figure 1b). First, nickel particles were added to a beaker containing a solution of sodium metasilicate pentahydrate, and SiO 2 was gradually deposited and attached to the surface of Ni particles under the control of hydrochloric acid. In order to form uniform core-shell Ni@SiO 2 units, polyvinylpyrrolidone (PVP) was added into the reaction solution before the formation of SiO 2 , which provides an additional steric hindrance effect. [25] As shown in Figure 1b, the matrix used is galinstan, one of the most important gallium-based LM, with a composition of Ga, In, and Sn in specific weight ratios (see in the Experimental Section). Initially, nanoparticles floated on the surface of galinstan Room-temperature liquid metals, such as galinstan, have become an emerging material in electronics requiring stretchability and deformability due to its excellent fluidity and conductivity. Eutectic gallium-indium-tin (galinstan)-based composites with certain metallic fillers can obtain magnetism. However, the alloying reaction between galinstan and metals leads to the solidification and reduction in stability of the composite. In this study, Ni@SiO 2 nanoparticles with the core-shell structure are used as fillers and galinstan as matrix. The obtained galinstan-Ni@SiO 2 paste is fairly stable and this is attributed to the silica shell, which acts as a barrier to isolate the direct contact between the Ni and galinstan. In addition, flexible circuits composed of as-prepared galinstan-Ni@...

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