Imagine a rubber band that was capable of snapping itself many times over, or a small robot that could jump up a set of stairs propelled by nothing more than its own energy. Researchers at the University of Massachusetts Amherst have discovered how to make materials that snap and reset themselves, only relying upon energy flow from their environment. The discovery may prove useful for various industries that want to source movement sustainably, from toys to robotics, and is expected to further inform our understanding of how the natural world fuels some types of movement.

Al Crosby, a professor of polymer science and engineering in the College of Natural Sciences at UMass Amherst and Yongjin Kim, a graduate student in Crosby’s group, along with visiting student researcher Jay Van den Berg from Delft University of Technology in the Netherlands, uncovered the physics during a mundane experiment that involved watching a gel strip dry. The researchers observed that when the long, elastic gel strip lost internal liquid due to evaporation, the strip moved. Most movements were slow, but every so often, they sped up. These faster movements were snap instabilities that continued to occur as the liquid evaporated further. Additional studies revealed that the shape of the material mattered, and that the strips could reset themselves to continue their movements.

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Polymer scientist Reika Katsumata at the University of Massachusetts Amherst recently was chosen to receive a prestigious 2021 Faculty Early Career Development (CAREER) award from the National Science Foundation (NSF). The five-year, $595,000 grant will support her investigations into fundamental problems bridging polymer science and engineering to better understand how different-sized molecules move in relationship to each other when they are heated.

As she explains, understanding such multi-scale polymer dynamics “is very important to how you form and shape polymers for use at room temperature. We are trying to understand what is going on at the molecular level. It’s a long-standing, sixty-year-old problem.”

Surprisingly, the molecular details are not known, Katsumata adds. “Every day I learn how little we know about materials and their relationships.” In particular, these dynamics are not straightforward for nanocomposites, she notes, and her lab will bring new knowledge at this level. Also, she has special expertise in fluorescence techniques that she will use in a series of experiments that for the first time combine two distinct methods to achieve new breakthroughs.

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Farmers and fruit growers are reporting that climate change is leading to increased ozone concentrations on the soil surface in their fields and orchards – an exposure that can cause irreversible plant damage, reduce crop yields and threaten the food supply, say materials chemists led by Trisha Andrew at the University of Massachusetts Amherst.

Writing in Science Advances, co-first authors Jae Joon Kim and Ruolan Fan show that the Andrew lab’s method of vapor-depositing conducting polymer “tattoos” on plant leaves can allow growers to accurately detect and measure such ozone damage, even at low exposure levels. Their resilient polymer tattoos placed on the leaves allow for “frequent and long-term monitoring of cellular ozone damage in economically important crops such as grapes and apples,” Andrew says.

They write, “We selected grapes (Vitis vinifera L.) as our model plant because the fruit yield and fruit quality of grapevines decrease significantly upon exposure to ground level ozone, leading to significant economic losses.” Ground-level ozone can be produced by the interaction between the nitrates in fertilizer and the sun, for example.

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Professor Thomas P. Russell, polymer science and engineering, was recently honored by the Neutron Scattering Society of America with its highest honor, the Clifford G. Shull Prize in Neutron Science, for “his pivotal role in the application of neutron reflectivity and small-angle neutron scattering to polymer science and his important work on behalf of the neutron scattering community.”

The prize is named in honor of Shull, who received the Nobel Prize in 1994 with Bert Brockhouse for seminal developments in the field of neutron science.

Russell says, “I was truly honored with this recognition and was happy to have been able to have made a significant contribution to the field that has advanced our understanding of long-chain molecules in thin film and at surfaces and interfaces. It was equally rewarding to have worked with outstanding scientists at Argonne National Laboratory (ANL) and the National Institute of Standards and Technology (NIST) and a talented group of post-doctoral fellows and graduate students.”

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