Liquid metal flowing

Liquid metal is a fascinating material that defies common sense, with unique properties used in applications from thermodynamics to electronics.

About this subject

Liquid metal refers to metals or alloys that remain fluid at relatively low temperatures, such as mercury, gallium, and sodium-potassium alloys. Mercury, with a melting point of -38.83 °C, has been historically used in thermometers and barometers, though its toxicity has led to replacements like gallium. Gallium melts at 29.76 °C (just above body temperature), allowing playful demonstrations like a spoon dissolving in warm water.

In industry, liquid metals serve as coolants in fast neutron nuclear reactors, such as sodium-cooled reactors operating up to 500 °C. Liquid sodium has high thermal conductivity and low vapor pressure but reacts violently with water, requiring careful engineering. Another emerging application is liquid metal batteries, which use layers of molten magnesium and antimony to store energy at grid scale, offering high density and long cycle life.

In scientific research, liquid metal is explored in microfluidics and soft robotics. Droplets of gallium alloys can be manipulated by electric or magnetic fields, creating self-healing circuits and flexible electronics. The nontoxic alloy Galinstan (gallium, indium, and tin) is liquid at room temperature and highly conductive, ideal for stretchable sensors and antennas. These innovations promise to revolutionize wearables and deformable devices.

Frequently Asked Questions

Which metals are liquid at room temperature?

Mercury (Hg), alloys like Galinstan (gallium, indium, tin), and the sodium-potassium alloy NaK are liquid at room temperature. Pure gallium melts at 29.76 °C, becoming liquid with slight warming.

Is liquid metal dangerous?

It depends. Mercury is toxic and bioaccumulative. Gallium and Galinstan are considered safe to touch but may stain surfaces. Liquid sodium reacts explosively with water, requiring handling in inert atmospheres.

How is liquid metal used in technology?

As coolants in nuclear reactors (sodium), in grid-scale batteries (magnesium-antimony), in flexible electronics (self-healing circuits), and in microfluidic systems for pumps and valves.