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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 7 FROG TONGUES INSPIRE ADVANCED ADHESIVES According to new research led by a team at Oregon State University (OSU), Corvallis, next-gen adhesive design could be based on frog tongue physiol- ogy. Frogs use their specialized tongues to capture prey with a force that can exceed their own body weight. This is due in part to the tongue being covered with a sticky mucus that functions as a pressure-sensitive adhesive. “This mu- cus is able to generate large adhesive forces in response to the high strain of retraction,” explains Joe Baio, assis- tant professor of bioengineering. “The goal of this study was to determine the chemical structure of the surface of this mucus after a tongue strike.” Mucus contains proteins called mucins that naturally form linear poly- meric chains that typically have dis- ordered secondary and tertiary struc- tures. Recent studies of frog tongue mucus resulted in visual observation of fibrils between the frog’s tongue and the target surface. “This fibril forma- tion indicates an induced change in the chemical structure of the mucus during tongue retraction,” says Baio. “And it is these fibrils that allow the mucus to generate strain-responsive adhesive forces by acting as molecular shock ab- sorbers for the tongue.” Collaborators at the Zoological In- stitute of the University of Kiel, Germa- ny, collected mucus samples from three adult horned frogs. Near edge x-ray absorption fine structure microscopy OMG! OUTRAGEOUS MATERIALS GOODNESS ICEPHOBIC COATING COMBATS WINTRY MIX University of Houston (UH) re- searchers developed a new theory in physics called stress localization, which they used to tune and predict the prop- erties of new materials. Based on those predictions, the team created a durable silicone polymer coating capable of re- pelling ice from any surface. Mechanical A new silicone polymer coating is capable of repelling ice from any surface. Courtesy of University of Houston. Horned frog capturing prey. Diagram from “Astronomy Explained Upon Sir Isaac Newton’s Principles, and Made Easy to Those Who Have Not Stud- ied Mathematics” by James Ferguson. Courtesy of AIP. images of the mucus layers were col- lected on the NIST beamline at the Na- tional Synchrotron Light Source. OSU researchers then characterized the sur- face chemistry, which confirms the for- mation of fibrils in response to tongue retraction, supporting previous classifi- cations of the frog sticky-tongue mech- anism as a pressure-sensitive adhesive. oregonstate.edu. RARE BOOKS ON PHYSICAL SCIENCE TO BE DIGITIZED The American Institute of Physics (AIP) received a three-year, $646,697 grant from the Alfred P. Sloan Founda- tion to make a unique collection of rare books in the physical sciences univer- sally accessible. The grant will enable AIP’s Niels Bohr Library & Archives to provide global, digital access to the Wenner Collection, a carefully curated repository that features 3800 volumes, dating back nearly five centuries. The books will be digitized and freely acces- sible to the public by December 2021. aip.org. engineering professor Hadi Ghasemi says the findings suggest a way to take trial and error out of the search for new materials, in keeping with the movement of materials science toward a physics-driven approach. The new coating uses elastic energy localization where ice meets the material, triggering cracks at the interface that slough off the ice. Ghasemi says it requires min- imal force to cause the cracks; for ex- ample, the flow of air over the surface of an airplane acts as a trigger. Testing shows the coating is mechanically du- rable, immune to ultraviolet rays, does not affect the aircraft’s aerodynamic performance, and will last more than 10 years. It is applied as a spray and can be used on any surface. uh.edu .