The ''energy gap'' in portable electronics is making micro fuel cells increasingly attractive, but the technology has been plagued by high costs, lack of standards, financial losses and bad publicity. For example, NTT DoCoMo (Tokyo) has reportedly backed away from teaming up with Aquafairy Co. (Osaka, Japan) to develop a water-powered fuel cell for mobile phones, according to sources. Last year, NTT DoCoMo took a 36.5 percent stake in Japanese fuel cell company Aquafairy.

This month, Medis Technologies Ltd. (New York) claimed it began commercial sales of its fuel cell line to Microsoft. But Medis was subsequently sued by shareholders, after it was revealed the firm only shipped a few products to Microsoft, which gave away the units at trade shows, according to sources.

The micro fuel cell ''industry has been long in promises, but short on deliveries,'' said Paul Zimmerman, chief executive of Angstrom Power Inc. (Vancouver, Canada), one of the emerging developers of micro fuel cells.

In an interview, Zimmerman said that micro fuel cells will become more of a ''mainstream'' product, when the overall business reaches a critical mass in the 2010 time frame. ''I think 2010 will be a watershed year,'' he said.

The worldwide micro cell fuel market is projected to range from $50-to-$100 million in sales by 2010, jumping to $100-to-$200 million by 2011, according to Angstrom Power. Until that time, there is expected to be a major shakeout in micro fuel cells, which consists of some 30 to 40 players in the arena right now, he said. Among the current major players in the market are Angstrom, Aquafairy, Teckion, Millennium Cell, MTI, Toshiba and others.

''It's an intriguing market, but the cost [of micro fuel cells] is the main problem,'' said Will Strauss, president of Forward Concepts Co. (Tempe, Ariz.), a market research firm. ''You also still can't take that stuff on a plane.''

Last year, the International Electrotechnical Commission (IEC) published a safety specification for small fuel cells, which supposedly opened the door for fuel cell use on passenger aircraft in the 2007 time frame. But it appears that this target date will get delayed for some time, due to safety issues.

Micro fuel cells are expected to constitute a $12 million market in 2006 and are predicted to reach $112 million in 2011, according to a new report by Innovative Research and Products (Stamford, Conn.). Among the various portable-product categories, iRAP predicts, micro fuel cells' use in PDAs will show the highest average annual growth rate though 2011, of 89.8 percent, followed by usage in camcorders, chargers and other consumer electronics, with a growth rate of 83.7 percent, and in mobile phone applications, at 50.7 percent.

Among the various technologies being pursued, direct methanol fuel cells will capture the largest share, followed by hydrogen-based fuel cells and those based on proprietary fuels, according to iRAP. A micro fuel cell (MFC) is an electrochemical device that converts the chemical energy of fuel, such as hydrogen or methanol or some patented fuel, into electrical energy, according to the research firm.

''Fuel cells have potentially higher energy density than batteries and promise a significant increase in power availability for portable electronics,'' according to the firm. ''However, developing a fuel cell system for portable electronics presents several engineering challenges.''

''There is some progress in the development of micro fuel cells,'' said Angstrom's Zimmerman. ''This is also an industry that has frustrated people.''