MICROSCOPIC submarines powered by bacteria could zip round the body
delivering drugs and zapping tumours, say researchers in Utah who are developing
a novel biomotor.
Earlier this month, the team presented their ideas at the Foresight
Conference on Molecular Nanotechnology in Bethesda, Maryland. The motor would be
ideal for navigating round the human body, says co-designer Eldrid Sequeira, a
nanotechnology researcher at Utah State University in Logan. In scenarios
reminiscent of the movie Fantastic Voyage, researchers eventually hope
to send robots round the body in the bloodstream to attack tumours with potent
drugs or scour out blocked arteries.
Other groups are also trying to make tiny subs, but with alternative power
supplies. A company called MicroTEC of Duisburg, Germany, for example, hopes to
use an external magnetic field to propel its craft around the body.
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The Utah team plan to attach swimming bacteria cells to vanes mounted on top
of a silicon disc sealed inside a tiny liquid-filled cylinder. Their natural
movement would push the disc around, turning a shaft and generating mechanical
energy. With bacterial cells as the power source the motors would only have to
be a few tens of micrometres wide.
Later, the team hopes to build biomotors using only the bacteria鈥檚 flagella
and their drive mechanisms (see Diagram).
By ditching the unneeded parts of the cells, they could shrink down the biomotors
to the 100-nanometre range and run even smaller robots in the future.
At the moment the team is simulating their biomotor on a computer to maximise
the power output of their design. But they hope to start building a prototype
within a few months. They are focusing on a wild strain of Salmonella
typhimurium because of its efficient mobility and relatively long lifespan
of about an hour without food.
However, they are still hunting for bacteria with even more favourable
traits. Sequeira says that feeding the bacteria to extend their life is not an
option, because reproduction would gum up the system. However this wouldn鈥檛 be
an issue if only the flagella were used.
Leslie Rubinstein, president of engineering design firm Renaissance
Technologies, based in Lexington, Kentucky, hopes to begin building medical
robots in the millimetre range within a year. 鈥淚t鈥檚 potentially viable, there鈥檚
no doubt about that,鈥� he says of the biomotor idea. It鈥檚 not the only option
though, other teams plan to harness bacterial chemical reactions for power. This
might make biological components unnecessary.