Ill. - A fuel cell designed by researchers at the
University of Illinois at Urbana-Champaign can operate
without a solid membrane separating fuel and oxidant,
and functions with alkaline chemistry in addition
to the more common acidic chemistry.
a battery, a fuel cell changes chemical energy into
electrical energy. While most fuel cells employ a
physical barrier to separate the fuel and oxidant,
the microfluidic fuel cell developed at Illinois utilizes
multi-stream laminar flow to accomplish the same task.
system uses a Y-shaped microfluidic channel in which
two liquid streams containing fuel and oxidant merge
and flow between catalyst-covered electrodes without
mixing," said Paul Kenis, a professor of chemical
and biomolecular engineering and a researcher at the
Beckman Institute for Advanced Science and Technology.
flowing through channels of microscale dimensions
behave differently than fluids flowing through the
much larger pipes found in home plumbing systems,
Kenis said. "At the microscale, there is no turbulence.
This laminar flow means streams of fuel and oxidant
can pass side by side without having a physical barrier
fuel cell consists of two electrodes (an anode and
a cathode), a fuel source and an oxidant. Reactions
at the anode liberate protons and electrons from hydrogen
atoms. The protons pass through the cell to the cathode,
where they recombine with electrons, which traveled
through an external circuit. Most fuel cells use a
polymer electrolyte membrane to separate the cathode
the Illinois fuel cell, the physical membrane is replaced
by the behavior of laminar flow. The fuel and oxidant
are brought together as liquid streams in the microchannel.
The protons and electrons diffuse through the liquid-liquid
configuration offers several advantages over PEM-based
fuel cells, including fewer parts and simpler design.
It also means that membraneless fuel cells are compatible
with alkaline chemistry.
as alkaline batteries outperform acidic batteries,
alkaline fuel cells should be superior to acidic fuel
cells, Kenis said. Several problems, however, have
prevented the widespread use of alkaline chemistries
in PEM-based fuel cells. Among them are poor permeability
of the membranes to hydroxide ions (which take the
place of protons in acidic fuel cells) and clogging
of the membranes from the formation of carbonates.
fuel cell doesn't suffer from these problems, because
it doesn't make use of a membrane," said Kenis,
who will describe the novel fuel cell at the spring
meeting of the American Physical Society, to be held
in Los Angeles, March 21-25.
applications such as power sources for portable computers
or battery chargers, multiple fuel cells will have
to be integrated to attain sufficient power levels.
the membraneless fuel cell is based on a phenomenon
that occurs only at the microscale, we can't just
scale up to larger dimensions," Kenis said. "Instead,
we need to scale out by creating arrays of many fuel
cells connected in series and in parallel."
included chemistry professor Andrzej Wieckowski, postdoctoral
research associates Lajos Gancs, Jayashree Ranga and
Piotr Waszczuk (now at Guidant), graduate students
Eric Choban (now at 3M) and Jacob Spendelow, and undergraduate
The work was funded by the Army Research Office, the
Beckman Institute, and the University of Illinois.
The researchers have applied for a patent.
James E. Kloeppel, Physical Sciences Editor 217-244-1073;