Liquid metal

Source: Wikipedia, the free encyclopedia.
For other uses, see Liquid metal (disambiguation).
Not to be confused with Liquidmetal.
Liquid gallium metal, at 30°C (86°F).

A liquid metal is a

metal alloy which is liquid at or near room temperature.[1]

The only stable liquid elemental metal at room temperature is mercury (Hg), which is molten above −38.8 °C (234.3 K, −37.9 °F). Three more stable elemental metals melt just above room temperature: caesium (Cs), which has a melting point of 28.5 °C (83.3 °F); gallium (Ga) (30 °C [86 °F]); and rubidium (Rb) (39 °C [102 °F]). The radioactive metal francium (Fr) is probably liquid close to room temperature as well. Calculations predict that the radioactive metals copernicium (Cn) and flerovium (Fl) should also be liquid at room temperature.[2]

Alloys can be liquid if they form a

eutectic, meaning that the alloy's melting point is lower than any of the alloy's constituent metals. The standard metal for creating liquid alloys used to be mercury, but gallium-based alloys, which are lower both in their vapor pressure at room temperature and toxicity, are being used as a replacement in various applications.[3][4]

Thermal and electrical conductivity

Alloy systems that are liquid at room

thermal conductivity far superior to ordinary non-metallic liquids,[5] allowing liquid metal to efficiently transfer energy from the heat source to the liquid. They also have a higher electrical conductivity that allows the liquid to be pumped more efficiently, by electromagnetic pumps.[6]
This results in the use of these materials for specific heat conducting and/or dissipation applications.

Another advantage of liquid alloy systems is their inherent high densities.

Viscosity

The viscosity of liquid metals can vary greatly depending on the atomic composition of the liquid, especially in the case of alloys. In particular, the temperature dependence of the viscosity of liquid metals may range from the standard

Vogel-Fulcher-Tammann equation
. A physical model for the viscosity of liquid metals, which captures this great variability in terms of the underlying interatomic interactions, was also developed.[7]

The electrical resistance of a liquid metal can be estimated by means of the Ziman formula, which gives the resistance in terms of the static structure factor of the liquid as can be determined by neutron or X-ray scattering measurements.

Wetting to metallic and non-metallic surfaces

Gallium wets skin, as shown here.

Once

corrosive to all metals except tungsten and tantalum, which have a high resistance to corrosion, more so than niobium, titanium and molybdenum.[9]

Similar to

agitation
. The oxide-free surfaces are bright and lustrous.

Applications

Because of their excellent characteristics and manufacturing methods, liquid metals are often used in wearable devices, medical devices, interconnected devices and so on.[3][4]

Typical uses of liquid metals include

barometers, heat transfer systems, and thermal cooling and heating designs.[11]
Uniquely, they can be used to conduct heat and/or electricity between non-metallic and metallic surfaces.

Liquid metal is sometimes used as a thermal interface material between coolers and processors because of its high thermal conductivity. The PlayStation 5 video game console uses liquid metal to help cool high temperatures inside the console.[12] Liquid metal cooled reactors also use them.

Liquid metal can be used for wearable devices[4][3] and for spare parts.[13]

Liquid metal can sometimes be used for biological applications, i.e., making interconnects that flex without fatigue. As Galinstan is not particularly toxic, wires made from silicone with a core of liquid metal would be ideal for intracardiac pacemakers and neural implants where delicate brain tissue cannot tolerate a conventional solid implant. In fact, a wire constructed of this material can be stretched to 3 or even 5 times its length and still conduct electricity, returning to its original size and shape with no loss.[14]

Due to their unique combination of high surface tension and fluidic deformability, liquid metals have been found to be a remarkable material for creating soft actuators.[15][16][17] The force-generating mechanisms in liquid metal actuators are typically achieved by modulation of their surface tension.[18][19][20] For instance, a liquid metal droplet can be designed to bridge two moving parts (e.g., in robotic systems) in such a way to generate contraction when the surface tension increases.[21] The principles of muscle-like contraction in liquid metal actuators have been studied for their potential as a next-generation artificial muscle that offers several liquid-specific advantages over other solid materials.[22]

See also

References

  1. ISSN 2365-709X
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  2. PMID 33576164
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  3. ^
    doi:10.1146/knowable-050322-2
    . Retrieved 31 May 2022.
  4. ^
    S2CID 236566966
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  5. ^ Kunquan, Ma; Jing, Liu (October 2007). "Liquid metal management of computer chips". Frontiers of Energy and Power Engineering in China. 1 (4): 384–402.
    S2CID 195071023
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  6. ISSN 0003-6951
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  7. S2CID 265424554
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  8. ASIN B0007AXLOA
    .
  9. ^ Lyon, Richard N., ed. (1952). Liquid Metals Handbook (2 ed.). Washington, D.C.{{cite book}}: CS1 maint: location missing publisher (link)
  10. ^ Liu, T.; S., Prosenjit; Kim, C.-J. (April 2012). "Characterization of Nontoxic Liquid-Metal Alloy Galinstan for Applications in Microdevices". Journal of Microelectromechanical Systems. 21 (2): 443–450.
    S2CID 30200594
    .
  11. ^ Liquid Metal Thermal Interface Materials
  12. ^ Grubb, Jeff (October 7, 2020). "PlayStation 5 uses liquid metal — here's why that's cool". VentureBeat. Retrieved December 19, 2020.
  13. ^ "Liquid Metal 3D Printing Makes Its Debut". Automation World. 2021-02-18. Retrieved 2022-07-23.
  14. PMID 33182535
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  15. S2CID 538906
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  16. ^ Liao, Jiahe (2022). Liquid metal actuators (Ph.D. thesis). Carnegie Mellon University.
  17. doi:10.1016/j.matt.2021.01.009
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  18. S2CID 231577619
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  19. doi:10.1063/1.4999113
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  20. PMID 25228767
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  21. PMID 35863909
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  22. PMID 37358049
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