ADVANCED MATERIALS & PROCESSES | NOVEMBER/DECEMBER 2023 12 MICROSCOPIC WAVEGUIDES Researchers at the University of Chicago discovered that a sheet of glass crystal just a few atoms thick could trap and carry light. The substrate was surprisingly efficient, and light could travel relatively long distances—up to a centimeter, which is quite far in the world of light-based computing. The research demonstrates what are essentially 2D photonic circuits and could open paths to new technology. The newly created system is a way to guide light—known as a waveguide—that uses extremely tiny prisms, lenses, and switches to guide the path of the light along a chip. In existing waveguides, photons always travel enclosed inside the waveguide. With this system, the scientists explain, the glass crystal is thinner than the photon itself—so part of the photon actually sticks out of the crystal as it travels. This approach makes it much easier to build intricate devices with the glass crystals, as light can be easily moved with lenses or prisms. The photons can also experience information about the conditions along the way. The researchers think these waveguides could have uses in microscopic sensors. They’re also interested in building very thin photonic circuits which could be stacked to integrate many more tiny devices into the same chip area. The glass crystal they used in these experiments was molybdenum disulfide, but the principles should work for other materials. uchicago.edu. NATURE INSPIRES SOFT ROBOTICS MUSCLES Based on a hydrogel, a new material system that functions similarly to a muscle has been developed by a research team from the Institute for Materials Science at Kiel University, Germany. The soft material can be reduced and enlarged again in a controlled manner in a short time, making it suitable for movement tasks in soft robotics. The team’s new hydrogels are thermoresponsive and, above a temperature of 32°C, they release water and reduce their volume. When the temperature EMERGING TECHNOLOGY The Association For Manufacturing Technology (AMT) and SME entered a strategic partnership to focus on workforce development, educational products and services, and student events. AMT’s education products and services will now be owned by SME and operated by its workforce development arm, Tooling U-SME. sme.org. BRIEF The hydrogel is built into a network of interconnected tubes that absorb and release water, while a graphene coating allows the material to be heated with electricity. Courtesy of Lena Saure. Co-author Hanyu Hong displays a glass crystal—visible as the thin line in the center of the plastic. Courtesy of Jean Lachat. drops, the hydrogel absorbs the water again and returns to its original volume. The process can be repeated any number of times, resulting in a kind of movement, similar to human muscles. This makes them interesting as actuator components for the development of new types of soft robots. To build the new materials system, the researchers from Kiel built a network of tiny tubes into their hydrogel. The numerous interconnected hollow tubes of a few micrometers in size allow the water to flow freely out of and into the hydrogel, thus enabling a rapid change in its volume, while an extremely thin graphene coating also makes the tubes electrically conductive. This way, researchers can heat the hydrogel with an electric current and control the water transport at the touch of a button. Due to the tissue-like properties of the hydrogel, it has potential applications in the medical sector, such as in robot-assisted surgery, artificial tissue construction, or also as an implant for controlled drug release in the human body. www.uni-kiel.de/en.
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