AMP_06_September_2021

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 2 1 6 4 3D PRINTSHOP The bridge was officially opened in July by Her Majesty Queen Máxima of the Netherlands. Courtesy of Adriaande Groot/MX3D. BRIDGE’S DIGITAL TWIN MONITORS HEALTH The world’s first 3D-printed steel bridge has a network of sensors that are tied to a digital twin tomonitor its struc- tural health. The futuristic award-win- ning bridge, designed by Joris Laarman Lab, has been placed over one of the oldest canals in Amsterdam’s city cen- ter, the Oudezijds Achterburgwal canal. Printed by Dutch technology company MX3D using robotic arms, the 12-meter-long bridge is equipped with more than 100 sensors to moni- tor strain, movement, vibrations, and weather conditions as people cross it. This sensor network is linked to a mathematical computer model forming a “digital twin” of the physical bridge and its digital representation. The data collected will help engineers assess how the bridge is faring, alerting them if problems occur and when mainte- nance might be required. The data will also provide input and lessons learned for future builds, helping designers un- derstand how 3D-printed steel could be used in more complex projects. Statis- tical methodology will be used to un- derstand more about the material itself and machine learning will be used to spot trends in the data pointing to po- tential changes, issues of maintenance, or necessary modifications. This digital twin moni- tors the bridge performance in real-time. The “smart” bridge, in effect, serves as a living lab- oratory, with pedestrians, cy- clists, and runners generating data every time they cross the bridge. The sensor network was designed and installed by a team from the Turing Data-Centric Engineering pro- gram that included structural engineers, mathematicians, computer scientists, and stat- isticians, and also researchers from the Cambridge Centre for Smart Infrastructure and Construction. The sensors are located in cham- bers under the bridge, as well as in the handrails and curls. Additional sensors are installed near the bridge. The ul- timate goal is to predict the behavior of the bridge and of the material from which it is built, enabling further opti- mization of this novel manufacturing technique. smartbridgeamsterdam.com . SELF-ADJUSTING MATERIALS MOVE LIKE A PLANT Researchers have developed a new process for producing movable, self-adjusting materials systems with standard 3D printers. These systems can undergo complex shape chang- es, contracting and expanding under the influence of moisture in a pre-pro- grammed manner. The scientists mod- eled their development based on the movement mechanisms of the climb- ing plant known as the air potato. With their new method, the team from the University of Freiburg and the Univer- sity of Stuttgart has produced its first prototype: a forearm brace that adapts to the wearer and which can be further developed for medical applications. 3D printing has been demonstra- ted to produce intelligent materials and material systems that remain in motion after printing, autonomously changing shape from external stimuli such as light, temperature, or moisture. This so- called 4D printing, in which predeter- mined shape changes can be triggered by a stimulus, immensely expands the potential applications of material sys- tems. These changes in shape are made possible by the chemical composition of the materials, which consist of stim- uli-responsive polymers. However, the printers and base materials used to pro- duce such materials systems are usu- ally highly specialized, custom made, and expensive. Now, using standard 3D printers, it is possible to produce materials sys- tems that react to changes in moisture. Given their structure, these materials systems can undergo shape changes in the entire system or simply in the indi- vidual parts. The researchers combined multiple swelling and stabilizing layers to realize a complex movement mecha- nism: a coiling structure that pulls tight- er by unfolding “pockets” as pressors and which can loosen up again on its own when the pockets release and the coiled structure returns to the open state. Researchers hope in the future in- expensive materials that also respond to other stimuli will become available for 3D printing and can be used with this process. www.intcdc.uni-stuttgart.de . The research team produced its first prototype, a forearm brace which adapts to the wearer. Courtesy of Tiffany Cheng/ ICD University of Stuttgart.