Critical Review on the Physical Properties of Gallium-Based Liquid Metals and Selected Pathways for Their Alteration

Abstract

Gallium-based liquid metals have gained plenty of attention in the scientific community due to their extraordinary properties. The most intriguing properties of liquid metals are high surface tension, density anomaly, high electrical and thermal conductivity, phase transition, and their temperature and low viscosity in combination with their low toxicity. Though there are many reports of the physical properties of gallium-based liquid metals, some of these are highly scattered and inconsistent. Therefore, we compile literature data of these aspects of gallium-based liquid metals, point out general relationships of these physical parameters, and unravel inconsistencies in the literature. Subsequently, we state reasons for the observed scatter and recommend science-based values researchers should employ. Furthermore, we discuss important dependencies between the physical parameters, introduce methods to alter the physical parameters, and introduce selected applications based on changing the physical properties. Finally, we point out open questions concerned with the physical parameters of liquid metals, which should be investigated in the future.

Self-Healable and Recyclable Dual-Shape Memory Liquid Metal–Elastomer Composites

“…As shown in Figure 2 b, the Ga–PU composite shows two melting temperatures in the DSC heating curve, and two crystallization temperatures in the DSC cooling curve. In the composite, the Ga microdroplets crystallize at a much lower temperature (–33.3 °C) during the cooling process, due to the supercooling and size effects [ 55 , 56 ], while melting is observed at 29.4 °C during the heating process. The other peak, at around −10.0 °C in the cooling curve, is attributed to the crystallization of PCL segments in the PU elastomer.…”

Anti-Freezing, Non-Drying, Localized Stiffening, and Shape-Morphing Organohydrogels

“…Liquid metal was chosen as it features fluidity (ca. 2 mP s), rendering it nearly infinitely bendable and stretchable, and high electrical conductivity (~3.4 × 10 4 S/cm) [ 41 ]. Furthermore, it remains in its liquid state far below its melting temperature of 10.5 °C (Galinstan) due to supercooling, and freezing is typically observed at temperatures below −20 °C [ 41 ].…”

“…2 mP s), rendering it nearly infinitely bendable and stretchable, and high electrical conductivity (~3.4 × 10 4 S/cm) [ 41 ]. Furthermore, it remains in its liquid state far below its melting temperature of 10.5 °C (Galinstan) due to supercooling, and freezing is typically observed at temperatures below −20 °C [ 41 ]. Therefore, both the liquid metal and the hydrogel are endowed with moldability at subzero temperatures, and should be an interesting approach for hydrogel soft electronics.…”

An ultrahigh fatigue resistant liquid crystal elastomer-based material enabled by liquid metal

“…In order to improve the fatigue resistance of LCE materials, we have tried to incorporate many reinforcing materials such as gold nanoparticles, carbon nanotubes, and carbon fibers into LCE matrices for introducing extra physical associations to strengthen the chain networks of LCEs [21], which however failed in substantially enhancing the fatigue resistance of LCEs. Recently, Ware, Majidi and other scientists described a liquid metal (LM)-doped LCE composite, which could realize electricdriven actuation based on the Joule-heating effect [26][27][28][29][30], and found that the introduction of LM [31][32][33] fillers into LCE materials could bring many advantages including fluidic nature, negligible toxicity, and flexibility. However, in order to achieve high electrical conductivity for electrothermal conversion, large quantity (~50 vol%) of LM microdroplet (~200 to 500 μm) fillers were incorporated into LCE matrices which did not markedly boost the mechanical performances of the corresponding composites [26].…”