A liquid that changes colour when exposed to a magnetic field could cheaply replace the colour components in conventional LCD monitors, claim US researchers.

The liquid contains tiny iron oxide particles coated with plastic. It is cheap and easy to make, and could also be used in flexible, rewritable, electronic paper, the researchers say.

Yadong Yin and colleagues at the Department of Chemistry at University of California, Riverside, US, created the liquid by coating particles of iron oxide – each about 100 nanometres in diameter – with a polymer and suspending the mixture in water.

The plastic coating means that each particle has a highly charged surface.

And, because the individual particles have the same charge, they repel each other in the solution. However, since iron oxide is also magnetic the particles will come together when exposed to a magnetic field.

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