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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 | F E B R U A R Y / M A R C H 2 0 1 9 1 4 MORE EFFICIENT LITHIUM BATTERIES Researchers from Penn State Uni- versity, State College, say dramatical- ly longer lasting, faster charging, and safer lithium metal batteries may now be possible. The team developed a 3D cross-linked polymer sponge that at- taches to the metal plating of a battery anode. Under additional strain, as with the fast-charging methods desired in electrical vehicles, lithium ion batteries are vulnerable to dendritic growth— needlelike formations that can reduce cycle life and potentially cause safety issues including fires or explosions. The researchers implemented a new approach involving the use of a polymer on the interface of lithiummet- al. Thematerial acts as a porous sponge that not only promotes ion transfer, but also inhibits deterioration, thus allow- ing themetal plating to be dendrite-free even in fast charge conditions. Practical applications of this work could enable more powerful and stable metal bat- tery technologies integral to everyday life, like increasing an electric vehicle’s distance range and enabling longer bat- tery life for smartphones. psu.edu . SUNFLOWER-INSPIRED SOLAR PANELS A group of scientists from Har- vard’s Wyss Institute for Biologically Inspired Engineering and John A. Paul- son School of Engineering and Applied Sciences, Cambridge, Mass., has har- nessed magnetic fields to control the molecular structure of liquid crystal elastomers (LCEs) and create micro- scopic 3D polymer shapes that can be programmed to move in any direction in response to multiple types of stimuli. The work could lead to the creation of a number of useful devices, including a new generation of solar panels that turn to follow the sun. The microstructures are made of LCEs cast into arbitrary shapes that can deform in response to heat, light, and humidity, and whose specific reconfig- uration is controlled by their own chem- ical and material properties. The team found that by exposing the LCE precur- sors to a magnetic field while they were being synthesized, all the liquid crystal- line elements inside the LCEs lined up along the magnetic field and retained this molecular alignment after the poly- mer solidified. Such programmed shape chang- es could be used to create encrypted messages that are only revealed when ENERGY TRENDS New LCE technology could lead to a new type of solar panel that follows the sun. Courtesy of Wikimedia Commons/ Micha Jost. heated to a specific temperature, ac- tuators for tiny soft robots, or adhe- sive materials whose stickiness can be switched on and off. The system can also cause shapes to autonomously bend in directions that would usually require the input of some energy to achieve. The team was also able to program their LCE shapes to recon- figure themselves in response to light by incorporating light-sensitive cross- linking molecules into the structure during polymerization. When the struc- ture was illuminated from a certain direction, the side facing the light con- tracted, causing the entire shape to bend toward the light. This type of self-regulated motion allows LCEs to deform in response to their environment and continuously reorient themselves to autonomously follow the light. One promising appli- cation of these multiresponsive LCEs is the creation of solar panels covered with microstructures that turn to follow the sun, resulting in more efficient light capture. wyss.harvard.edu . A cheap and effective new catalyst developed by researchers at the University of California, Berkeley can generate hydrogen fuel from water just as efficiently as platinum, currently the best yet most expensive water-splitting cata- lyst. The new catalyst, composed of nanometer-thin sheets of metal carbide, is manufactured using a self-assembly process that relies on an unusual ingredient: gelatin. Because the recipe is so simple, it could easily be scaled up to produce large quantities. news.berkeley.edu . BRIEF A 3D cross-linked polymer sponge attaches to the metal plating of a lithium ion battery anode, allowing ion transfer and limiting deterioration. Courtesy of Donghai Wang.