A nanoscale robot with a clutch can engage or disengage its engine, allowing for more precise control over its motion. It could be used to kill harmful cells.
Tiny clutches already exist in nature 鈥� for example, the bacterium Bacillus subtilis has long, hair-like structures called flagella, each attached to a rotating molecular engine. 鈥淥nce [the bacteria] arrive at their target area, they will take a rest,鈥� says at Yonsei University in Seoul, South Korea. 鈥淭hey use a molecular clutch such that the engine is still on, but there is no force transmission into the flagella, so they are saving energy while not completely shutting off their system.鈥�
Now, Cheon and his colleagues have created their own version 鈥� a nanomachine powered by magnetic fields, with a clutch made from DNA.
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The engine consists of a nanoparticle made from gold and iron oxide that rotates in a magnetic field and is surrounded by a spherical gold cage. The cage is around 200 nanometres across, which is similar in size to a typical virus. Cheon and his team attached single strands of DNA to the inside of the cage and to the outside of the nanoparticle motor. When the engine is given a trigger, such as a specific molecule or increased salt levels, the single DNA strands on both surfaces fuse together and the nanoparticle connects to the cage, engaging the clutch.
Cheon and his team tested the engine with the clutch engaged and found that, when rotating, it could apply a force of around 15 piconewtons. In experiments with cancerous human bone cells, the team found that this was enough force to mechanically activate certain cell receptors, meaning that the robot could be used to make cells divide or die. One limitation is that the robot can鈥檛 currently navigate and can only rotate in place, but Cheon says his team is now working on navigation.
It is a clever design, says at the University of Oxford, and it could eventually be used to create nanomachines with gear systems that can do even more. 鈥淭heir device provides a world of opportunities for engineering complex emergent features,鈥� he says.
Nature Nanotechnology
