There's a lot of energy in ethanol, which
is non-toxic and can be made cheaply from corn.
Researchers from Saint Louis University, who earlier this year
developed a fuel cell using enzymes to generate electricity from ethanol,
have built a microchip-based version of the device.
The trick to constructing the biofuel cell was creating a sheltered
environment for the enzymes, which are fairly sensitive. The researchers
coated the carbon anode, or positive electrode, of the fuel cell with
polymethylene green, an electocatalyst, then added a nafion membrane containing
the immobilized enzyme alcohol dehydrogenase.
The biofuel cell showed an electrical potential of 0.34 volts
and current density of 53 microamps per square centimeter, according to
the researchers. Multiple cells can be stacked, and the device can be
integrated into a computer chip.
The microchip biofuel cell could eventually be used in place of
rechargeable batteries. Instead of recharging by plugging into a wall
outlet like batteries, the biofuel would be recharged by adding a few
milliliters, or thousandths of a liter, of alcohol. The micro fuel cell
could also be used to power sensors and labs-on-a-chip.
The researchers' prototype consists of a 200-micron-wide, three-centimeter-long
channel in a plastic chip. The bottom of the channel is lined with the
carbon anode, which is covered by the electric catalyst and membrane.
The researchers tested the fuel cell by measuring the electricity generated
as one microliter, or millionths of a liter, per minute of ethanol flowed
through the channel. A drop of water contains about 50 microliters.
The biofuel cell's enzyme catalysts are renewable. Most fuel cells
catalyze reactions with metals, which are relatively expensive and not
The work is scheduled to appear in an upcoming issue of Lab-on-a-Chip.
-TECHNOLOGY RESEARCH NEWS