Engineers have created metallic nanofish that are inspired by the swimming style of real fish, and could be used to carry drugs to specific sites of the body.

The nanofish are 100 times smaller than grains of sand, and are constructed from gold and nickel segments linked by silver hinges. The two outer gold segments act as the head and tail fin, while the two inner nickel segments form the body. Each segment is around 800 nanometres long, a nanometre being one billionth of a metre.

When an oscillating magnetic field is applied, the magnetic nickel parts move from side to side. This swings the head and the tail, creating an undulating motion that pushes the nanofish forward (see video). Speed and direction can be controlled by altering the strength and orientation of the magnetic field.

Several other research groups are also developing ‘nanoswimmers’ for drug transport. Most of these use helical propellers inspired by the corkscrew tails of bacteria, but experiments have shown that the propulsive mode of nanofish is more efficient.

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