Molecules/Matter & Energy

Electrifying ink
New electricity-conducting ink can be used to make flexible electronic devices. Researchers from the University of Illinois at Urbana-Champaign and Lawrence Livermore National Laboratory created a silver-nanoparticle ink that smoothly flows through a rollerball pen tip without leaking, skipping or clogging and remains stable for months. The team then drew electrodes on ordinary office paper and, with a few other ingredients, used the paper to create a flexible sheet of light-emitting diodes and a 3-D radio-frequency antenna. Such a strategy could work for making paper-based batteries and medical diagnostic devices, the researchers report online June 20 in Advanced Materials. —Rachel Ehrenberg

Fossil pigments leave trace
A dark brown pigment leaves a trail of metal breadcrumbs in fossils that’s detectable millions of years later, an international team reports online June 30 in Science. Using an intense X-ray beam to zap fossils of ancient bird relatives, a fossil squid and other creatures revealed copper, zinc and other trace metals in tissues believed to harbor the brown pigment eumelanin. These metals are also found in eumelanin-rich regions of modern animals, such as a squid’s ink sac. The findings suggest a method for uncovering color markings on long-dead creatures, perhaps revealing how the animals camouflaged themselves or advertised to mates. —Rachel Ehrenberg

Plutonium’s conspirator
Scientists have long suspected plutonium of having an accomplice for getting into cells, and now the culprit has been fingered: iron. Iron aids and abets plutonium by holding a cellular doorway open, a team from Illinois and Washington reports online June 26 in Nature Chemical Biology. Once it’s inside cells, plutonium continues to expose organs and tissues to radiation for decades. Plutonium poisoning is typically treated with compounds that scavenge the element from the body, but the iron-transport system might make a good additional therapeutic target, perhaps preventing the toxic stuff from accumulating in cells to begin with.—Rachel Ehrenberg

Superelastics can take the heat
Superelastic alloys put under tremendous stress have an unrivaled ability to snap back into shape afterward, and now one of them can also take the heat. A new material remains superelastic over a broad range of temperatures (–196 to 240 degrees Celsius). This alloy can be used in cars, planes, spacecraft and in any environment subject to extremely high and low temperatures. And because the new material is made of iron and other common metals, large quantities could be incorporated into buildings to dampen vibrations caused by earthquakes, researchers at Tohoku University in Japan report in the July 1 Science. —Devin Powell

Molecules in knots
New knots fashioned from molecules would leave even a Boy Scout tongue-tied. Researchers in England and Slovenia grabbed onto stringy surface defects and looped them around spherical particles in a liquid crystal. Laser tweezers cut, manipulated and fused these loops, creating interconnected trefoils, Stars of David and other shapes. These knots might be useful for creating new soft materials or for studying how DNA and biological materials tangle, the researchers report in the July 1 Science. —Devin Powell