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[tvoivozhd <tvoivozd AT infionline.net>]

 Alcohol fuel cell goes micro

        
        * December 29, 2004/January 5, 2005*
**

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 
renewable.

The work is scheduled to appear in an upcoming issue of /Lab-on-a-Chip/. 
-TECHNOLOGY RESEARCH NEWS