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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 | S E P T E M B E R 2 0 1 9 7 POLAR BEARS INSPIRE NEW INSULATOR To survive in Arctic conditions, polar bears must rely on insulation supplied by their own fat, skin, and fur. For engineers, polar bear hair is an ideal template for synthetic mate- rials that could lock in heat just as ef- ficiently. Now, materials scientists at the University of Science and Technol- ogy of China (USTC) have developed such an insulator, reproducing the structure of individual hairs with the goal of building a material composed of many hairs for applications in archi- tecture and aerospace. Unlike the hair of other mammals, polar bear hairs are hollow. Examined under a microscope, each one has a long, cylindrical core punched through its center. The shapes and spacing of these cavities are not only responsible for their distinctive white coats, but also the source of re- markable heat-holding capacity, water resistance, and stretchiness. To imitate this structure and scale it to a useful size, researchers manu- factured millions of hollowed-out car- bon tubes, each equivalent to a single strand of hair, and wound them into OMG! OUTRAGEOUS MATERIALS GOODNESS a spaghetti-like aero- gel block. Compared to other aerogels, the new hollow-tube design is lighter weight and more resistant to heat flow, say researchers. The new material is also ex- traordinarily stretchy, even more than the hairs themselves, further boosting its usefulness. http://en.ustc.edu.cn. SNAIL MUCUS LEADS TO NEW ADHESIVE Inspired by snail mu- cus, scientists at University of Pennsyl- vania, Lehigh University, and the Korea Institute of Science and Technology created a material similar to superglue that they describe as “intrinsically re- versible.” Achieving both strong adhe- sion and reversibility is challenging. Ac- cording to Professor Anand Jagota, this is especially true of hydrogels, which are 90% water. He says that adhesives usually fall into one of two classes: strong but irreversible, like superglues, or reversible and reusable but weak. The team reports that when hy- drated, the softened gel they created conformally adapts to the target sur- face by low-energy deformation, which is then locked upon drying in a manner similar to the action of the epiphragm of snails. An epiphragm is a tempo- rary structure created by snails and Eucalyptus bark extract is now being used to synthesize graphene sheets. Courtesy of RMIT University. Snails served as inspiration for a new adhesive similar to superglue. mollusks. Made of dried mucus, it holds in moisture during periods of inactivity and enables snails to adhere to surfaces such as rocks. The scientists show that reversible, super-strong adhesion can be achieved from a nonstructured ma- terial when the criterion of shape adap- tation is met. According to the research- ers, the new material can be applied to both flat and rough target surfaces. lehigh.edu . GENERATING GRAPHENE FROM EUCALYPTUS A new method for producing graphene was recently developed by scientists at RMIT University, Australia, and the National Institute of Technol- ogy, Warangal, India. The technique uses Eucalyptus bark extract and is less expensive and more sustainable than existing synthesis techniques, accord- ing to researchers. RMIT lead scientist Suresh Bhargava says the new tech- nique could lower the cost of production from $100 per gram to just 50 cents per gram. Professor Vishnu Shanker from the National Institute of Technology, Warangal, says the “green” chemistry avoids the use of poisonous reagents, possibly paving the way for the use of graphene in biocompatible materials. When tested in a supercapacitor, the graphene created by the new technique matched the performance and quali- ty of traditional graphene. www.rmit. edu.au. Electron microscopy image of the bioinspired carbon tube aerogel. Courtesy of Hui-Juan Zhan.