Molecules/Matter & Energy

Clear batteries, mucus busters, a 3-D invisibility cloak and more in this week's news

Breaking up is hard for goo
Scientists have hit upon a couple of compounds that weaken the stiff mucus that afflicts the lungs of many cystic fibrosis patients. Mucus usually forms a sticky blanket that traps and helps clear inhaled particles, but in people with cystic fibrosis, fibrous bundles of DNA make mucus stiff, thick and tough to clear. Two extracts from alginate, a primary ingredient in algae cell walls, disrupt mucous interactions, Catherine Nordgård and Kurt Draget of the Norwegian University of Science and Technology report in an upcoming Biomacromolecules. The compounds may be useful for modifying mucus in the respiratory tract and beyond —Rachel Ehrenberg

Bats filter out clutter
Like college students, echolocating bats can tolerate clutter. The big brown bat has evolved an acoustic trick to ignore potentially confusing leaves and trees when pursuing its prey through dense foliage. By recording the calls of trained bats, tweaking the frequencies and playing the sounds back, Mary Bates of Brown University and colleagues found that bats filter out certain sounds — much like human beings ignoring distractions in their peripheral vision. The bats ignore echoes returning from objects to the side or at a great distance, which tend to be missing higher frequencies. This acoustic technique, reported in the July 29 Science, could be useful for designing better sonar technologies. —Devin Powell

3-D invisibility cloak
The latest invisibility cloak can conceal a 3-D object seen from any direction. Previous carpet cloaks could disguise only something sitting on a surface, like a bump on a log. David Rainwater and collaborators at the University of Texas at Austin made the new cloak, a tube with a diameter of 1.25 centimeters, out of plasmonic metamaterials — synthetic structures with wobbly electrons on the their surfaces that bend electromagnetic radiation in unusual ways. This new plasmonic cloak manipulates microwaves, but the concept should hold for infrared and optical wavelengths as well, the researchers report online July 19 at —Devin Powell

Transparent lithium ion battery
A new see-through lithium-ion battery is a step toward making cell phones, e-readers and other electronic devices fully transparent. While scientists have already made transparent circuits, batteries have remained stubbornly opaque. That’s because electrodes must be thick to store energy. But Yuan Yang and collaborators at Stanford University developed a new electrode out of strips of material too thin for the eye to see, arranged in a grid much like tic-tac-toe. The flexible prototype is 60 percent transparent. Its energy density — the amount of energy it stores in a given volume — is only 3 percent that of a typical cell phone battery, but could theoretically be increased by a factor of 10, researchers report in an upcoming PNAS. —Devin Powell

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