Science Concentrates SYNTHESIS MATERIALS
▸ Octopus-inspired robot skin goes 3-D
Chemists build a triple norbornane
Engineers have used the fluid and flexible nature of the octopus as inspiration for designing soft-bodied robots and artificial skins that change color or glow. Now, researchers have captured another facet of octopus camouflage: three-dimensional skin texturing. Cephalopods such as octopuses and cuttlefish raise specialized bumps on their skin, called papillae, to blend into their surroundings. One papilla can form a variety of shapes, such as a cone or trilobe, depending on how the muscles within it are arranged. To create an artificial skin that mimics this 3-D camouflage strategy, a team led by Robert F. Shepherd of Cornell University embedded laser-cut
As molecular explorers, chemists often venture out into “chemical space” to see what strange new discoveries they can make. To assist in these efforts, researchers have devised algorithms that take a prescribed set of elements and number of atoms and work through all the possible combinations leading to stable molecules that are synthetically feasible. Using the GDB-11 database, which constructs molecules containing C, N, O, or F and containing up to 11 framework atoms, a team led by Marcel Mayor of the University of Basel decided to zoom in on polycyclic hydrocarbons lacking three- or four-membered rings. This structural SO2C6H5 CH3O Cl motif is sometimes O CH3O found in natural + products that have O O potential as drug canOCH CH O 3 3 O didates. Among the 124 molecules that C6H5O2S popped up in the data-
one day make skins that form multiple shapes.—EMMA HIOLSKI
A 22- by 22-cm silicone membrane (top) inflates to form river rock shapes (bottom). fiber mesh into a mold containing a silicone liquid. The mesh—a common nonwoven nylon embroidery stabilizer—provides structural support to cured silicone when the material is inflated and, depending on the laser-cut pattern, helps create a targeted shape (Science 2017, DOI: 10.1126/science. aan5627). The engineers used an algorithm, developed by lead author James H. Pikul, now at the University of Pennsylvania, to determine which pattern to cut in the mesh and created shapes including cones, river rocks, succulent plants, and topographical maps. These skins could help disguise robots or even serve as customizable shipping material. Though each skin can form only one predesigned shape, Shepherd says replacing the mesh with inflatable tubing, or using a voltage gradient instead of air, could
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C&EN | CEN.ACS.ORG | OCTOBER 16, 2017
CHEMICAL SENSING
▸ Electronic ring detects chemical threats The field of wearable sensors is booming. Many people, for example, use Fitbits on their wrists to track their physical activity. Less attention has been devoted to wearables for defense applications, but Joseph Wang and coworkers at the University of California, San Diego, have now taken a step toward addressing that gap (ACS Sens. 2017, DOI: 10.1021/ acssensors.7b00603). The researchers designed,
constructed, and tested a battery-powered ring that monitors for explosives and nerve agents in air and liquids and sends wireless alerts, to a cell phone for instance, when it finds them. The outer surface of the ring has printed electrodes on it. A semisolid agarose hydrogel on the surface promotes analyte diffusion to the electrodes, which are linked to miniaturized electronics inside the device that interpret the electrochemical signals and transmit the data. The ring uses chronoamperometry and fast square-wave voltammetry to monitor nitroaromatic and peroxide explosives and organophosphate nerve agents. The researchers believe the device’s capabilities can be extended to other hazardous agents. “The miniaturization and integration of the electronics and sen-
With this ring, I thee protect: The sensors are capable of monitoring for explosive residues and chemical nerve agents.
C R E D I T: S CI E NC E ( RO CKS ) ; COU RTESY OF JO S EP H WA NG ( R I N G )
base search, only three had no real-world Trinorbornane counterparts. One of these 9 steps compounds, an intricate symmetrical saturated C11H16 7% overall yield molecule, was “particularly appealing and eye catching,” so the researchers decided to try to make it (Chem. Commun. 2017, DOI: 10.1039/c7cc06273g). The compound’s scaffold consists of two norbornane units that share a pair of neighboring edges, an arrangement that coincidentally results in a third norbornane subunit. Using a total synthesis strategy similar to the way chemists go about preparing natural products, the researchers succeeded in making a racemic mixture of the chiral compound, which they have named trinorbornane, in nine steps with 7% overall yield.—STEVE RITTER
