Cloaking devices—it's not just 'Star Trek' anymore

Cloaking devices play a pivotal role in many sci-fi television programs. Scientists are now working to take this technology from the dramatic realm of science fiction and make it real. Amanda D. Hanford, at Pennsylvania State University, is taking the introductory steps to make acoustic ground cloaks. These materials redirect approaching waves around an object without scattering the wave energy, concealing the object from the sound waves.

During the 175th Meeting of the Acoustical Society of America, being held May 7-11, 2018, in Minneapolis, Minnesota, Hanford will describe the physics behind an underwater acoustic shield designed in her lab.

Hanford and her team set out to engineer a metamaterial that can allow the sound waves to bend around the object as if it were not there. Metamaterials commonly exhibit extraordinary properties not found in nature, like negative density. To work, the unit cell—the smallest component of the metamaterial—must be smaller than the acoustic wavelength in the study.

"These materials sound like a totally abstract concept, but the math is showing us that these properties are possible," Hanford said. "So, we are working to open the floodgates to see what we can create with these materials."