Researchers at Duke University are using 3D printed devices constructed with metamaterials to create passive 3D acoustic holograms from a single source. The device they’ve created is modular, not unlike a Lego building block design, and allows for sounds to pass through and then create a hologram on the other side. This hologram design is small and robust, and suitable for more simple medical applications. Read more at 3DPrint.com: https://3dprint.com/154311/duke-3dp-acoustic-holograms/