It may be hard to believe, but that transparent disk in the photo above is actually a fully functioning speaker. A team of researchers at Harvard's School of Engineering and Applied Sciences have pioneered a never before seen application of ionic conductivity by creating a see-through artificial muscle that can produce sounds spanning the entire audible spectrum. While ionic conduction isn't a novel idea, it's been considered impractical due to the fact that ionic materials react poorly to high voltage. The team, which included postdoctoral research fellows Jeong-Yun Sun and Christoph Keplinger (pictured above), circumvented that obstacle by placing a layer of rubber between two sheets of transparent conductive gel, allowing the system to work with both high voltage and high actuation, two qualities necessary for sound reproduction. Theoretically, soft machine technology such as this can be used to do much more than play Grieg's Peer Gynt, particularly in the fields of robotics, mobile computing and adaptive optics. To watch it in action, check out the video after the break.