AMP_04_May_June_2021_Digital_Edition

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 | M A Y / J U N E 2 0 2 1 1 2 PROCESS TECHNOLOGY STRENGTHENING ADAPTIVE MATERIAL Inspired by bone, scientists at the University of Chicago’s Pritzker School of Molecular Engineering developed a gel material that strengthens when ex- posed to vibration. They were able to significantly strengthen the areas ex- posed to movement—specificity that could lead to new adhesives and better ways of integrating implants within the body. The new material is a polymer gel mixed with thiolene reactors and zinc oxide piezoelectric particles. When exposed to mechanical stress, the particles transduce energy and create a thiolene reaction. The re- sulting crosslinking essentially forms a second network inside the material, strengthening it. Though the material begins as a soft, collagenous material, as the vibration increases, the material is further strengthened. The team was able to increase the strength of the ma- terial by 66 times, resulting in a materi- al that was close to the stiffness of the interior parts of bone. The strengthen- ing property of the new gel could lead to materials that can selectively stiff- en—and a new way to design struc- tures. The group is examining how to use the material to better integrate ar- tificial materials into the human body. uchicago.edu . BIOMEDICAL HYDROGELS Researchers at UCLA created a new method to make synthetic bioma- terials that mimic the internal struc- ture, elasticity, strength, and durability of tendons and other biological tissues. The two-pronged process improves the strength of existing hydrogels that could be used to create artificial ten- dons, ligaments, and cartilage that are 10 times tougher than natural tissues. The new hydrogels could also provide coating for implanted or wearable med- ical devices to improve their fit, com- fort, and long-term performance. Although the hydrogels consist of mostly water, they are more dura- ble than Kevlar and rubber, which are both 100%polymer. The UCLA-led team used freeze-casting followed by a treat- ment to aggregate and crystalize poly- mer chains into strong fibrils. The re- sulting new hydrogels have a hierarchy of multiple structures, which enables the material to be stronger and more stretchable. This method is highly cus- tomizable and could replicate various soft tissues in the human body. The researchers used polyvinyl al- cohol, a material approved by the U.S. Food and Drug Administration, to make their hydrogel prototype. In addition to biomedical applications, this advance- ment may hold potential for surgical machines or bioelectronics that oper- ate innumerable cycles, and 3D print- ing of previously unachievable config- urations, thanks to the hydrogel’s flex- ibility. In fact, the team demonstrated that such 3D-printed hydrogel architec- tures could transform into other shapes pending changes in temperature, acidi- ty, or humidity. Acting as artificial mus- cles, they are much more resilient and could exert great force. ucla.edu . This new gel material (white) mimics bone and gets stronger when exposed to vibration. Courtesy of Z. Wang et al./ Nature Materials. Scientists at University College London and the Italian Institute of Technology created a temporary tattoo with the same light-emitting technology used in TV and smartphone screens, paving the way for a new type of “smart tattoo” with a range of potential uses. The new version uses organic light-emitting diodes (OLEDs) and is fabricated onto temporary tattoo paper, then transferred to a new surface by being pressed and dabbed with water. www.ucl.ac.uk . BRIEF OLED tattoo devices. Courtesy of Barsotti/Italian Institute of Technology. Microscopic, enhanced photo of artificial tendon material. Courtesy of Sidi Duan et al./UCLA.