Colloidal liquid metal alloys of gallium, with melting points below room temperature, are potential candidates for creating electrically conductive and flexible composites. However, inclusion of liquid metal micro‐ and nanodroplets into soft polymeric matrices requires a harsh auxiliary mechanical pressing to rupture the droplets to establish continuous pathways for high electrical conductivity. However, such a destructive strategy reduces the integrity of the composites. Here, this problem is solved by incorporating small loading of nonfunctionalized graphene flakes into the composites. The flakes introduce cavities that are filled with liquid metal after only relatively mild press‐rolling (<0.1 MPa) to form electrically conductive continuous pathways within the polymeric matrix, while maintaining the integrity and flexibility of the composites. The composites are characterized to show that even very low graphene loadings (≈0.6 wt%) can achieve high electrical conductivity. The electrical conductance remains nearly constant, with changes less than 0.5%, even under a relatively high applied pressure of >30 kPa. The composites are used for forming flexible electrically‐conductive tracks in electronic circuits with a self‐healing property. The demonstrated application of co‐fillers, together with liquid metal droplets, can be used for establishing electrically‐conductive printable‐composite tracks for future large‐area flexible electronics.

In nature, snowflake ice crystals arrange themselves into diverse symmetrical six-sided structures. We show an analogy of this when zinc (Zn) dissolves and crystallizes in liquid gallium (Ga). The low-melting-temperature Ga is used as a “metallic solvent” to synthesize a range of flake-like Zn crystals. We extract these metallic crystals from the liquid metal solvent by reducing its surface tension using a combination of electrocapillary modulation and vacuum filtration. The liquid metal–grown crystals feature high morphological diversity and persistent symmetry. The concept is expanded to other single and binary metal solutes and Ga-based solvents, with the growth mechanisms elucidated through ab initio simulation of interfacial stability. This strategy offers general routes for creating highly crystalline, shape-controlled metallic or multimetallic fine structures from liquid metal solvents.

Liquid metal dispersion stabilized by natural phenolics for conductive paper composites has been demonstrated.

With growing research interest in liquid metals, such as Ga and Ga-based alloys, understanding their behaviours at reduced dimensions is becoming of more fundamental significance, especially for exploiting their properties...

202101500is known for its near room temperature melting point of 29.76 °C and presents much lower toxicity comparing to liquid metal mercury. In recent decades, Ga has attracted growing research interests due to its fascinating properties including fluidity, metallic electrical and thermal conductivities. [1] Gallium and its alloys have shown applications in microfluidics, [2] sensing, [3] catalysis, [4] self-healing materials, [5] soft composites for biomedical devices, wearable electronics, [6] and electromagnetic wave shielding materials. [7] Gallium and its alloys are attractive materials for establishing soft composites for flexible and malleable electronics and sensors due to their variable electrical resistance under the modulation by a mechanical load. Especially, Ga and Ga-based alloy droplets, embedded into polymeric matrices, can deform alongside the polymeric materials, unlike solid particles. [8] In other words, by combining fluidic behaviors and metallic nature, Ga and its alloys offer distinct advantages that no other traditional fillers can offer. However, these Ga-based liquid metals also present a native thin passivating oxide layer on their surfaces, which drastically reduces the electrical conductivity of the composites. The insulating properties of Ga-based droplets can be overcome by mechanical rupturing of the oxide layer via pressing, [9] stretching, [10] expansion, [11] and twisting. [12] Therefore, Ga and its alloys have been commonly investigated as electrically conductive fillers for the formation of pressure and motion sensing elastomer composites.A variety of polymers, such as silicone (including polydimethylsiloxane (PDMS)), [13] polyvinyl alcohol (PVA), [6a,14] and poly(methyl methacrylate) (PMMA), [15] have been utilized as matrices for the inclusion of Ga-based fillers. However, a large volume fraction of liquid metal additives and mechanical activation are commonly required to achieve high sensitivity for the elastomer composites. [5a,6a,16] Additionally, such elastomers have intrinsic stretchability limitations. As compared to elastomers, sponge materials allow for much higher degrees of compressibility and reversibility, which present new opportunities for the synthesis of highly sensitive pressure-sensing devices and other electrical components.The distribution of the liquid metal additives into polymeric matrices was shown to affect the resulting thermal and electrical properties. [16][17] Typical strategies to disperse liquid Liquid metal droplets of gallium (Ga) and Ga-based alloys are traditionally incorporated as deformable additives into soft elastomers to make them conductive. However, such a strategy has not been implemented to develop conductive sponges with real sponge-like characteristics. Herein, polyurethanebased sponges with Ga microdroplets embedded inside the polyurethane walls are developed. The liquid phase (at 45 °C) and solid phase (at room temperature) transition of the Ga fillers shows the temperature-dependent functional variations in the mec...

Liquid metals and alloys with high-aspect-ratio nanodimensional features are highly sought-after for emerging electronic applications. However, high surface tension, water-like fluidity, and the existence of self-limiting oxides confer specific peculiarities to their characteristics. Here, we introduce a high accuracy nanometric three-dimensional pulling and stretching method to fabricate liquid-metal-based nanotips from room- or near-room-temperature gallium-based alloys. The pulling rate and step size were controlled with a resolution of up to 10 nm and yielded different nanotip morphologies and lengths as a function of the base liquid metal alloy composition and the pulling parameters. The obtained nanotips presented high aspect ratios over lengths of a few microns and apexes between 10 and 100 nm. The liquid metal alloys were found confined within nanotips with about 10 nm apexes when vertically pulled at 100 nm/s. An amorphous gallium oxide skin was shown to cover the surface of the nanotips, while the liquid core was composed of the initial liquid metal alloys. The electrical contact established at the nanotips was characterized under dynamic conditions. The liquid metal nanotips showed an Ohmic resistance when a continuous liquid metal channel was formed, and a controllable semiconductor state corresponding to a heterojunction formed at the junction between the liquid metal phase and the gallium oxide semiconductor skin. The variable threshold voltages of the heterojunction were controlled via stretching of the nanotips with a 10 nm step resolution. The liquid metal nanotips were also used for establishing soft electronic junctions. This novel method of liquid metal nanotip fabrication with Ohmic and semiconducting behaviors will lead to exciting avenues for developing electronic and sensing devices.

The separation and sensing of alkali metal ions from aqueous lithium resources is of great importance for building future renewable and lithium-based energy storage technologies. As such, interest arises for...

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