#chalcogenides

Engineers at MIT have developed a new material that can be repeatedly stretched and flexed without losing its optical properties.

Researchers at MIT and several other institutions have developed a method for making photonic devices — similar to electronic devices but based on light rather than electricity — that can bend and stretch without damage. The devices could find uses in cables to connect computing devices, or in diagnostic and monitoring systems that could be attached to the skin or implanted in the body, flexing easily with the natural tissue.

The findings, which involve the use of a specialized kind of glass called chalcogenide, are described in two papers by MIT Associate Professor Juejun Hu and more than a dozen others at MIT, the University of Central Florida, and universities in China and France. The paper is slated for publication soon in Light: Science and Applications.

Hu, who is the Merton C. Flemings Associate Professor of Materials Science and Engineering, says that many people are interested in the possibility of optical technologies that can stretch and bend, especially for applications such as skin-mounted monitoring devices that could directly sense optical signals. Such devices might, for example, simultaneously detect heart rate, blood oxygen levels, and even blood pressure.

The Institute for Basic Science research team headed by the associate director of CCES, KIM Chang Young, presented the possibility of unifying theories to explain the working mechanism of iron- based superconductors.

Their research was published in Nature Materials on August 16th. Superconductors are a relatively new concept; they were brought to prominence in the late 80’s when two Nobel Prize winners discovered a new superconducting material. The basic principle of superconductivity arises when a superconducting material is cooled to a fairly low critical temperature allowing an electric current to flow without resistance.

Building on a Nobel Prize

The Nobel Prize winners reported their superconducting material - oxides which contain copper and rare earth metals - becomes a superconducting material below -250° Celsius, higher than the previous temperature of -269° Celsius. This led to a boom in developing similar materials for commercial use. Today’s research has moved on greatly; oxides are replaced with iron-based superconductors which are cheaper to mass produce and also permit a current to flow unabated. To understand the working mechanism of iron-based superconductors scientists have to significantly raise the transition temperatures to source the reason for the increase. Many researchers initially work on the assumption that the nesting effect is a dominant factor, especially in the case of pnictide superconductors {PSD}. Later, scientists discovered another type of superconductor, chalogenide superconductors {CSD}. Since it turned out that CSD is not subject to the nesting effect, the discovery of CSD generated controversy on the mechanism of their superconductivity. The nesting effect states when the surface temperature is increased, electrons become unstable thereby altering their properties both electrically and magnetically, allowing conductors to turn into superconductors.