BY CHRIS SUTTON
UCLA Today
In a world where the future in technology is
moving in the direction of small-scale science, the emerging
realm of micro-scale devices could completely change the medical,
automotive and aerospace industries — except for one tiny,
but sizable obstacle.
No battery yet exists that will provide long-lasting
power and still fit inside devices that are smaller than the
width of a human hair — microelectromechanical systems
or MEMS that could one day be implanted in your body to deliver
drugs or protect transplanted cells.
Professor Bruce Dunn from the Henry Samueli School of Engineering
and Applied Science believes a radical new design for a lightweight,
rechargeable battery, based on three-dimensional geometry, will
provide power to such small devices.
“Our team of engineers and chemists is
establishing the enabling science for a new battery that represents
a real paradigm shift,” said Dunn, of the Department of
Materials Science and Engineering.
Currently, electronic devices such as laptop
computers and cell phones use traditional, two-dimensional batteries,
each with positive and negative electrodes stacked one upon
another like sheets of paper. To give the battery more power,
more layers of electrodes have to be added, making the battery
bigger and heavier.
While this may work for laptops, Dunn explained,
shrinking these batteries down to the size required to power
a MEMS wouldn’t provide enough energy.
The UCLA-led team proposes changing from two-dimensional
sheets of electrodes to rods arranged in a three-dimensional
array in which hundreds of rods are stacked next to each other
like tubes on a flatbed truck. Each rod is only a thousandth
of a centimeter in size. This design keeps the battery compact
and the distance the ions have to travel short, which is important.
“A more efficient path for the movement
of ions means less power loss and a longer-lasting battery,”
Dunn said.
The researchers are designing a battery roughly
five millimeters in size, about the size of a sesame seed. “We’re
going to use fairly well-known lithium battery materials,”
Dunn said. “The hard part is fabricating it into a structure.
That’s where the real engineering emphasis will be.”
Using micromachining techniques, Professor C.J.
Kim and his students from the Department of Mechanical and Aerospace
Engineering are creating silicon chips to be used as molds.
The electrode materials are placed in the molds, left to harden.
Then the silicon mold is etched away, leaving behind the three-dimensional
battery electrode structure.
The need for a lightweight battery that will
not sacrifice energy for small size is only going to grow as
the size of cell phones and video cameras shrinks. Already,
up to 35% of a laptop’s total weight comes from its battery,
and manufacturers are busily searching for lighter alternatives.
Dunn believes it may be at least five years before 3-D battery
designs make it into the consumer market.
The team, which is in the first year of a five-year
collaborative effort funded by a $4-million grant from the Office
of Naval Research, includes researchers from the universities
of Florida and Utah and other UCLA faculty members, including
Professor Fred Wudl, holder of the Courtalds Chair in Chemistry,
and Assistant Professor Sarah Tolbert, both from the Department
of Chemistry and Biochemistry, who are leading the effort toward
3-D processing of the electrode materials in the battery.
“It’s exciting,” Dunn said.
“We have the opportunity to take electrochemical materials
and designs in a new direction.”
