How does liquid metal work?

Metallic droplets that make intricate shapes

Image credit: Steve Jurvetson

Iron is common – it’s why your blood tastes metallic. So you might be surprised to know that it also helps to form hedgehog-shaped droplets.

To make these spiky ‘ferrofluids’, people mix tiny iron particles into a liquid with molecules called surfactants – which is what gives washing-up liquid its cleaning power. The surfactants stop the iron clumping together.

When you put a drop of the liquid near a magnet, the magnet moves tiny iron particles along magnetic force lines with gaps between, like you see with dry iron filings. However, in liquids the molecules gently attract each other. When they meet the air, this creates a force known as surface tension. Surface tension and gravity pull against the magnetic forces, keeping the iron particles in the droplet. Spikes form because ferrofluids channel magnetic force lines, and troughs form in between. Such ferrofluids can be used in electronics and engineering, in products containing magnets, such as speakers.

How ferrofluids spike

Forces wrestle each other and find balance in unique forms

Image credit: Future PLC (click to expand)

This article was originally published in How It Works issue 132, written by Andy Extance 


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