Science Concentrates MATERIALS
‘Venus flytrap’ soft robot gets a grip Autonomous light-powered device inspired by the carnivorous plant grabs reflective objects Pity the poor insect that wanders onto a Venus flytrap. Just a couple false steps into the carnivorous plant’s trigger hairs, and the leaves snap shut, dooming the bug. Inspired by the Venus flytrap’s ability to distinguish between insects and other stray bits of matter, Tampere University of Technology scientists Arri Priimagi, Hao Zeng, and Owies M. Wani have created a soft robot that acts with the same sort of autonomy. Their optical flytrap distinguishes
between objects that reflect or scatter light and those that do not before grabbing the reflective ones. “It’s very difficult in soft robotics to develop systems that make decisions by themselves,” says Priimagi, who led the research team. Most soft robots, he says, don’t react to their environment but instead require some sort of external activation. His team’s solution was to incorporate
Field of view
ed al fe c i t p
k bac
O Elastomer actuator
Light-induced bending Optical fiber An open optical flytrap closes when a reflective “insect” enters its field of view, causing light to scatter onto the liquid crystalline elastomer actuator, which bends in response, trapping the insect.
an optical fiber into a liquid crystalline elastomer. When the light strikes a reflective object, it reflects back onto the liquid crystalline elastomer, triggering a photochemical isomerization in the elastomer’s azobenzene components. The isomerization events release heat, causing the liquid crystals to lose their orientation and bend the elastomer, which makes the device grip the reflective object in as little as 200 microseconds (Nat. Commun. 2017, DOI: 10.1038/ncomms15546). Jian Chen, an expert in soft robotics at the University of Wisconsin, Milwaukee, says Priimagi and coworkers’ use of an optical feedback loop to make their soft robot autonomous is creative. “This work represents very significant progress in the field of soft robotics,” Chen says. Priimagi explains that the optical flytrap was originally developed out of scientific curiosity. But the device might find use in quality control during microfabrication, gripping and removing tiny objects that don’t reflect light as they should. The optical flytrap can currently clamp down on objects hundreds of times as heavy as the elastomer, but Priimagi would like to boost that by an order of magnitude. He’d also like to create grippers that distinguish between differently colored objects and ones that snap shut as quickly as Venus flytraps—about twice as fast as the current optical flytrap.—BETHANY HALFORD
ANALYTICAL CHEMISTRY
Oxygen-17 NMR spectroscopy is one tool that chemists can use to study the structure and reactivity of various organic and inorganic compounds. But 17O’s low natural abundance—merely 0.04%—requires enriching samples with the isotope, a process that is often costly and time-consuming. One solution to the challenge of 17O labeling may be mechanical: Combine a reagent with a stoichiometric amount of 17O-enriched water and grind the mixture in a ball mill, suggests a team led by Danielle Laurencin of the Institut Charles Gerhardt Montpellier (Angew. Chem. Int. Ed.
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C&EN | CEN.ACS.ORG | MAY 29, 2017
Engl. 2017, DOI: 10.1002/anie.201702251). Grinding reagents in a ball mill to induce reactions is a form of mechanochemistry that has gained popularity in recent years as a relatively quick and convenient way to make some organic and inorganic compounds. As the balls collide in the mill, effects such as shear stress and increased temperature may help stimulate chemistry at the interfaces between particles. Laurencin and colleagues produced 17O-enriched metal oxides by combining a metal hydroxide with less than two equivalents of 17O-enriched water, grinding the reagents for 30 minutes, then heating the
material to convert it to the metal oxide. Enriching 60 mg of Mg(OH)2 or Ca(OH)2 to 17O levels suitable for solid-state NMR analyses cost the team about $10. For 17O NMR of organic compounds, the researchers focused on carboxylic acids, which frequently turn up in biomolecules and metal ligands, such as those in metal-organic frameworks. The researchers first ground the organic compounds with 1,1’-carbonyl-diimidazole to activate the carboxylic groups and then milled the material with 17O-enriched water. The whole procedure took less than two hours.—JYLLIAN KEMSLEY
CREDIT: ADAPTED FROM NAT. COMMUN.
Grinding in 17O labels
