ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2023 12 SOFT ROBOTICS BREAKTHROUGH At Carnegie Mellon University, Pittsburgh, engineers are studying softbotics—a new generation of soft machines and robots manufactured by multifunctional materials that have integrated sensing, actuation, and intelligence. In a recent breakthrough, they developed a soft material with metal-like conductivity and self-healing properties that is the first to maintain enough electrical adhesion to support digital electronics and motors. The research team used the material, a liquid-metal filled organogel composite, in three applications: a damage- resistant snail-inspired robot, a modular circuit to power a toy car, and a reconfigurable bioelectrode to measure muscle activity on different locations of the body. The fully untethered snail robot used the self-healing conductive material on its soft exterior, which researchers embedded with a battery and electric motor to control motion. During the demonstration, the team severed the conductive material and watched as its speed dropped by more than 50%. Because of its self-healing properties, when the material was manually reconnected, the robot restored its electrical connection and recovered 68% of its original speed. The material can also act as a modular building block for reconfigurable circuits. Finally, the team demonstrated the material’s ability to be reconfigured to obtain electromyography (EMG) readings from different locations on the body. Because of its modular design, the organogel can be refitted to measure hand activity on the anterior muscles of the forearm and to the back of the leg to measure calf activity. This opens pathways to tissue-electronic interfaces like EMGs and EKGs using soft, reusable materials. The team says their work represents a breakthrough in the fields of robotics, electronics, and medicine. cmu.edu. PRINTABLE PEROVSKITE SOLAR CELLS The potential for perovskite solar cells to be manufactured at scale has been unlocked by scientists at Swansea University, U.K., who developed a lowcost and scalable carbon ink formulation while searching for an alternative to conventional evaporated gold electrodes. Using slot die coating in a roll-toroll (R2R) process, the researchers established a way to create fully print- EMERGING TECHNOLOGY A new study from the U.S. Geological Survey and Apple determined the rock-to-metal ratios for rare earth elements, describing how much ore and waste rock must be mined and processed to produce refined mineral commodities. This ratio is critical to understanding mine waste and potential environmental impacts. The report is published in the Journal of Cleaner Production, online at https://bit.ly/3L3TBjZ. BRIEF A close-up of a sample of the new fully roll-to-roll (R2R) coated device. Courtesy of Swansea University. Robotic snail powered by breakthrough self-healing, electrically conductive material. Courtesy of Carnegie Mellon University College of Engineering. able perovskite photovoltaics. The devices with carbon electrodes provided a similar photovoltaic performance to gold electrodes as part of a smallscale device on a rigid glass substrate, with power conversion efficiencies of 13%–14% and the additional benefits of outperforming at higher temperatures and having better long-term stability. The new fully R2R coated device, which was printed onto a 20-meter-long flexible substrate, produced a stabilized power conversion efficiency of 10.8%. “Perovskite solar cells show great promise in the drive toward cleaner, greener energy,” lead photovoltaic researcher Trystan Watson says. “The ability to produce a fully working device entirely in-line makes high- volume manufacturing easier and more economical and is a big step toward their commercialization. It unlocks the idea of a manufacturing process where a solar ink is added on one end and a solar cell emerges from the other.” www.swansea.ac.uk.
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