Smartphones may soon have the capability of seeing through walls courtesy of a tiny, low-cost imaging chip, researchers say. Two electrical engineers at the California Institute of Technology have invented tiny inexpensive silicon microchips that generate and radiate high-frequency electromagnetic waves, called terahertz waves. These waves are in a largely unused region of the electromagnetic spectrum between microwaves and far-infrared radiation and can penetrate a host of materials without the ionizing damage of X-rays, a Caltech release said. When built into hand-held devices, they could lead to a range of applications in fields ranging from homeland security to wireless communications to healthcare, the researchers said.