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A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 1 7 5 BUTTERFLIES INSPIRE BETTER SOLAR CELLS A team of researchers at the Cal- ifornia Institute of Technology, Pasa- dena, and the Karlsruhe Institute of Technology, Germany, improved the ef- ficiency of thin film solar cells by mim- icking the architecture of rose butterfly wings. Using an electron microscope, the team found the wings to be covered with scales pockmarked with holes. In addition to making the wings lighter, the holes scatter the light striking them, allowing the butterfly to absorb more of the sun’s heat. Inspired by the but- terfly design, researchers created sim- ilar structures in their lab using sheets of hydrogenated amorphous silicon. A top layer with tiny holes of various sizes causes light to scatter and strike the silicon base below. The new design enables picking up roughly twice as much light as previous attempts, say re- searchers. caltech.edu , kit.edu/english. WORM SECRETIONS FORM RECYCLABLE FIBERS Velvet worms spray a sticky liquid to ward off enemies like spiders, and as soon as their prey tries to wriggle Are you working with or have you discovered a material or its properties that exhibit OMG - Outrageous Materials Goodness? Send your submissions to Frances Richards at frances.richard s@asminternational.org. OMG! OUTRAGEOUS MATERIALS GOODNESS Velvet worms capture prey with a secre- tion that forms hard polymer threads as the victim tries to free itself. Courtesy of Alexander Baer/Nature Communications 2017. IRIDIUM AIDS BATTLE AGAINST CANCER According to new research by a collaboration between the University of Warwick, UK, and Sun Yat-Sen Univer- sity, China, cancer cells can be target- ed and destroyed with metal from the asteroid that wiped out the dinosaurs. The research team demonstrated that iridium can be used to kill cancer cells by filling them with a deadly version of oxygen, without harming healthy tissue. The scientists created a com- pound of iridium and organic material, which can be directly targeted towards cancerous cells, transferring energy to the cells to turn the oxygen (O 2 ) inside into singlet oxygen, which is poison- ous. The process is triggered by shin- ing visible laser light through the skin onto the cancerous area—reaching the compound’s light-reactive coating and activating the metal to start filling the cancer with singlet oxygen. The team found that after attacking a model tu- mor of lung cancer cells, the activated organic-iridium compound had pene- trated and infused into every layer of the tumor to kill it. www.warwick.ac.uk. out of the slimy threads, the struggle causes the threads to harden—leav- ing no hope of escape. “The shear forces gen- erated by the struggle cause the slime to hard- en into stiff filaments,” says Alexander Bar, a doctoral student at the University of Kassel, Ger- many. Bar works closely with researchers from the nearby Max Planck Institute of Colloids and Interfaces to study this behavior. It turns out that the nanoparticles from these velvet worm secretions form recyclable polymer fi- bers: The polymerized slime threads can be dissolved in water within a few hours of drying and then be drawn again from the recovered slime. The redrawn threads behave exactly like fresh secretions under the influence of shear forces—they harden. Researchers say the velvet worms could serve as a model for manufacturers of synthetic polymers and could teach them some- thing about sustainable production of synthetic materials. www.mpikg.mpg . de/en. The rose butterfly, common in India, has soft black wings that keep it warmduring cool periods. Inset shows SEM image of butterfly nanoholes. Courtesy of Radwanul Hasan Siddique, KIT/Caltech. Artist rendering. Courtesy of University of Warwick/Mark Garlick.