"It's a bit like flattening wads of Play-Doh, one layer at a time, and then rolling them up together, like a jelly roll," says Xiao. "This allows you to pack more of your active materials into a small space without increasing the resistance."
The new battery is a little more than half the weight of batteries currently used in acoustic fish tags just 70 milligrams, compared to about 135 milligrams and measures six millimeters long by three millimeters wide. The battery has an energy density of about 240 watt hours per kilogram, compared to around 100 for commercially available silver oxide button microbatteries.
The battery holds enough energy to send out an acoustic signal strong enough to be useful for fish-tracking studies even in noisy environments such as near large dams. The battery can power a 744-microsecond signal sent every three seconds for about three weeks, or about every five seconds for a month. It's the smallest battery the researchers know of with enough energy capacity to maintain that level of signaling.
The batteries also work better in cold water where salmon often live, sending clearer signals at low temperatures compared to current batteries. That's because their active ingredients are lithium and carbon fluoride, a chemistry that is promising for other applications but has not been common for microbatteries.
Last summer in Xiao's laboratory, scientists Samuel Cartmell and Terence Lozano made by hand more than 1,000 of the rice-sized batteries. It's a painstaking process, cutting and forming tiny snippets of sophisticated materials, putting them through a flattening device that resembles a pasta maker, binding them together, and rolling them by hand into tiny capsules. Their skilled hands rival those of surgeons, working not with tissue but with sensitive electronic materials.
A PNNL team led by Deng surgically impla
|Contact: Tom Rickey|
DOE/Pacific Northwest National Laboratory