CHEMISTRY 1000 Topics of Interest #2: A Cloaking Device?

Invisibility The concept of invisibility has fascinated humans for centuries. The list of stories involving magical creatures who could make themselves invisible is nearly endless. The idea of an invisibility cloak or cape, allowing a human to become invisible, has appeared in many fantastical stories as well. As technology advanced, the idea that we could make an invisibility device became popular in science fiction. In Star Trek, for example, entire ships could be rendered invisible by a “cloaking device”. Several years ago, researchers published a step closer to this being reality! A. Cho Science (2006) 312, 5777 J.B. Pendry, D. Schurig and D.R. Smith Science (2006) 312,

Invisibility What does it mean for something to be invisible? The literal definition would be that we can’t see it. What has to happen? Light waves striking the object from the viewers side cannot be allowed to “bounce back” to the viewer. Light waves from behind the object must pass around it in such a way that it looks like they went right through it. Essentially, the object must bend light! Scientists at Duke University designed an object that is partially capable to doing this. In the following video, they talk about their object (the key to which is what it’s made of – not its shape) and show its effect on microwaves: communications/2531-duke-universitys-invisibility-cloak- video.htm# A. Cho Science (2006) 312, 5777 J.B. Pendry, D. Schurig and D.R. Smith Science (2006) 312,

Invisibility Follow-up courtesy of Jeff Schaffer (section D, Fall 2008): Work has also been done on this topic at the Univeristy of California, Berkeley involving making materials with negative refractive indices: “While all materials found in nature have a positive refractive index, these man-made metamaterials have a negative one. Viewing an object through water causes it to appear displaced because of water's refractive index. A negative refractive index means that displacement is backwards -- if water's refractive index were negative, underwater objects would appear to be out of the water entirely.” (from reference below) “Researchers say the breakthrough not only could take them a step closer to creating cloaking devices that render objects invisible to the human eye, but could aid in the development of higher-resolution optical imaging, as well as nanoscale circuits for high-powered computers.” (from reference below) POPULAR SCIENCE Invisibility Cloak Swirls Closer to Reality New materials developed at Berkeley bend light in unnatural -- almost supernatural -- ways By Jaya Jiwatram