[tt] Yeast-powered fuel cell feeds on human blood - tech - 01 April 2009 - New Scientist
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Wed Apr 1 20:55:49 CEST 2009
Yeast cells feeding on the glucose in human blood might one day power implants
such as pacemakers. A living source of power that is able to regenerate itself
would eliminate the need for regular operations to replace batteries.
Now that reality is a step nearer. A team at the University of British Columbia
in Vancouver, Canada, has created tiny microbial fuel cells by encapsulating
yeast cells in a flexible capsule. They went on to show the fuel cells can
generate power from a drop of human blood plasma.
Such fuel cells would be especially useful for devices, such as intraspinal
microelectrodes for treating paralysis, which need to be implanted in places
where replacing a battery is tricky, says Mu Chiao, who co-authored the paper
with Chin-Pang-Billy Siu, also at UBC.
Conventional fuel cells rely on high-temperature catalysts such as platinum to
strip electrons from fuels and generate a current. The idea with microbial fuel
cells, which are being investigated as large-scale power sources is to exploit
the wide range of low-temperature catalysts – enzymes – found in living cells.
The easiest way to do this is to simply steal the electrons produced when cells
start to break down food. This can be done with the help of an "electron
mediator" – a chemical small enough to pass into cells, grab some electrons, and
diffuse out again.
The new fuel cell consists of a colony of Saccharomyces cerevisiae – the kind of
yeast commonly used in brewing and baking – encapsulated in a fuel cell made of
a form of silicone called polydimethylsiloxane (PDMS). The prototype is 15
millimetres square and 1.4 mm thick.
Methyl blue – a chemical often used to stain biological samples – is used as the
electron mediator. This steals some of the electrons produced when the yeast
metabolises glucose and delivers them to the anode side of the cell – creating a
small current. On the cathode side, hydrogen ions that diffuse out of the yeast
cells combine with oxygen to create water.
To increase the surface area of the electrodes and thus boost the fuel cell's
power output, the team used a silicon etching technique to create "micropillars"
roughly 40 micrometers square and 8 micrometers high (see image).
The yeast-based fuel cell produces around 40 nanowatts of power, compared to the
microwatt a typical wristwatch battery might produce, Chaio says. That might be
enough power for some devices if it were coupled with a capacitor to allow
energy to be stored. The yeast could also be genetically engineered to boost its
This is a step in the right direction, but huge challenges remain, says Lars
Angenent, who works on microbial fuel cells at Cornell University.
For instance, to keep the yeast cells healthy, their waste products will need to
be removed without allowing any harmful substances to leach out into the blood
stream. "I think people will figure this out. This is a first step," he says.
Journal reference: Journal of Microelectrical Systems (DOI:
Singularity Institute for Artificial Intelligence
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