Bubbles Propel Microrockets Through Acid


Micromotors could give "the runs" a different meaning. Researchers just designed tiny micromotors that propel themselves through acidic environments using hydrogen bubbles. That means they can work in stomach acid.

The research group, led by University of California San Diego nanoengineering professor Joseph Wang, constructed each micromotor from extremely tiny plastic tubes containing a thin layer of zinc. The structure measures nearly 10 micrometers in length. When the engineers put the little rocket in an acidic solution, the zinc lost electrons, creating hydrogen bubbles. Then, zoom.

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As the pH in the solution decreases, the rocket's speed increases. Wang and his colleagues say their micromotor can travel up to 1,050 micrometers per second, which is about 100 body lengths per second. That seems fast to me.

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Although they sound a bit like Alka-Seltzer tablets, the researchers were able to control the rocket's by adding magnetic layers to the outer structure. Through manipulation of the magnetic field, the rockets could even pick up and release tiny plastic "cargo." PhysOrg embedded a couple of videos showing the micromotor in action that look like M.C. Escher drawings.

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The researchers' work was recently published (abstract) in the Journal of the American Chemistry Society. Apparently this was the first time a micromotor has been built that didn't require extra chemical fuel. 

The researchers say they think these devices could have a bunch of biomedical and even industrial applications. Imagine putting one in your stomach to do some reconnaissance. Next, Wang has indicated that the next step is to extend the micromotor's lifetime. Much like effervescent tablets, it stops bubbling after a couple minutes.

Image: The circle highlights a microscale rocket transporting tiny plastic cargo, captured in a time-lapse video. Credit: Wei Gao, et al. and the American Chemical Society.

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