May_June_AMP_Digital

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 1 9 1 2 EQUATION-SOLVING METAMATERIALS Researchers from the University of Pennsylvania, Philadelphia, recently demonstrated a metamaterial device that can solve equations. The field of metamaterials involves designing com- plicated composite structures, some of which can manipulate electromagnetic waves in ways that are impossible in naturally occurring materials. Here’s how it works: The “photonic calculus” encodes parameters into the properties of an incoming electromagnetic wave and sends it through a metamaterial device; once inside, the device’s unique structure manipulates the wave in such a way that it exits encoded with the solution to a pre-set integral equation for the arbitrary input. Lead researcher Nader Engheta and his team have demonstrated such a device for the first time. Their experi- ment was conducted with microwaves, as the long wavelengths allowed for a macro-scale device that was easier to build. The principles behind their findings, however, can be scaled down to light waves, eventually fit- ting onto a microchip. Such metamaterial de- vices would function as analog computers that operate using light instead of electricity. They could solve inte- gral equations orders of magnitude faster than their digital counterparts, all while using less pow- er. “Even at this proof-of-concept stage, our device is extremely fast compared to electronics,” says Engheta. “With mi- crowaves, our analysis has shown that a solution can be obtained in hundreds of nanoseconds, and once we take it to optics the speed would be in picosec- onds.” upenn.edu. STRETCHABLE ELECTRONICS HOLD PROMISE Next-generation wearable devic- es could be significantly improved by the development of stretchable electronics. The technology has potential applications in health- care, energy, and the military, but challenges exist with regard to finding suitable materials and manufacturing methods. One obstacle to making stretchable electronics is that each compo- nent must endure being com- pressed, twisted, and applied EMERGING TECHNOLOGY A new center established by Cornell University, Ithaca, N.Y., and the Air Force Research Laboratory (AFRL), Wright-Patterson Air Force Base, Ohio, aims to dis- cover the atomic secrets of beta-gallium oxide, a promising material for enabling electronic devices to handle dramatically more power. The center is supported by a three-year, $3 million grant from AFRL with additional funds from Cornell and an option for a two-year extension. cornell.edu , wpafb.af.mil/afrl. BRIEF to uneven surfaces while maintaining performance, according to researchers from Wuhan University, China. Various stretchable electronic components are now in development. For example, low- cost stretchable conductors and elec- trodes are being made from silver nanowires and graphene. However, an urgent technical problem is the need for stretchable energy conversion and storage devices such as batteries. One alternative to batteries is stretchable nanogenerators, which can produce electricity from vibrations in the im- mediate environment, such as wind or body movements. Stretchable solar cells could also be used to power wear- able electronic devices. By integrating multiple stretch- able components, such as temperature, pressure, and electrochemical sensors, it is also possible to create a material resembling human skin that could use signals from sweat, tears, or saliva for real-time, noninvasive healthcare mon- itoring. This material could also be used for smart prosthetics or robots with enhanced sensing capabilities. www. en.whu.edu.cn . Metamaterial demonstration device—a two-foot square made of polystyrene plastic. Thin-film transistor matrix, shown relaxed (left) and stretched to approximately 60% (right). Courtesy of N. Matsuhisa et al., Nature Communications, July 25, 2015/Creative Commons. AFRL-Cornell Center for Epitaxial Solutions leadership team.