Lithium, the lightest metal, when paired with oxygen from the atmosphere, makes for a tantalizing partnership in a lightweight battery. In theory, this “lithium-air battery” offers several times the energy per kilogram of today’s lithium-ion batteries. But so far, in laboratory tests the lithium gets distracted by dead-end chemical reactions that prevent the batteries from recharging. A one-shot battery is fine for a wristwatch, but not for a next-generation electric vehicle.
Last month, researchers in Rome and Seoul, South Korea, reported designing a lithium-air battery that did not have the recharging problem, achieving approximately 100 charge and discharge cycles with little capacity loss. And this week, a research team led by chemist Peter Bruce of the University of St. Andrews, in Scotland, reports in the journal Science a differently designed lithium-air battery that reached 100 cycles, losing only 5 percent of its capacity in the process. Bruce says that these recent results show that lithium-air batteries can sustain “a truly reversible reaction.” The group measured the mix of chemicals involved, showing that the lithium was really being recycled through a reversible substance, lithium peroxide (Li2O2), during each charge and discharge. Continue reading
Bioengineers are getting better at replacing and enhancing body parts, but so far they’ve struggled to power implantable bionics without resorting to clunky batteries. But because blood carries energy in the form of electron-rich molecules like glucose and delivers it to all parts of the body, it is a tempting target for researchers. Chemist Evgeny Katz of Clarkson University, in Potsdam, N.Y., and his colleagues recently tested a new kind of electrode, which, when implanted in Neohelix albolabris snails and immersed in the snails’ blue, bloodlike hemolymph, produced a small, steady supply of electricity over a period of months. The researchers reported the work in March in the Journal of the American Chemical Society. Continue reading
Monitoring a wound as it heals should get easier thanks to a new kind of optical fiber that could become a part of everyday bandages. The fiber’s coating alters in color in response to changes in acidity, a key health indicator in wounds. The core of the fiber carries light to and from an attached device, which caregivers could use to monitor a wound in real time, says Bastien Schyrr, a Ph.D. student in biomedical engineering at the University of Fribourg, in Switzerland, who last month presented results of a laboratory trial in which the enhanced bandage detected acidity changes in a solution containing human serum. Continue reading
Coaches admire athletes for showing a lot of heart, and poets praise the organ’s passions, but engineers see the human cardiovascular system otherwise. The heart is a pump in a prime location, brimming with energy for the taking, says biomedical engineer Alois Pfenniger. So together with colleagues at the University of Bern and the Bern University of Applied Sciences, in Switzerland, Pfenniger has tested small turbines designed to fit inside a human artery, like an implantable hydroelectric generator. Continue reading