Smartphones may soon have the capability of seeing through walls courtesy of a tiny, low-cost imaging chip, US 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 Monday. 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. \"Using the same low-cost, integrated-circuit technology that\'s used to make the microchips found in our cell phones and notepads today, we have made a silicon chip that can operate at nearly 300 times their speed,\" electrical engineering Professor Ali Hajimiri said. \"These chips will enable a new generation of extremely versatile sensors.\" Waves in the terahertz frequency range can easily penetrate packaging materials and yield high-resolution images of hidden objects, and can also detect the chemical fingerprints of pharmaceutical drugs, biological weapons, or illegal drugs or explosives, Hajimiri and postdoctoral scholar Kaushik Sengupta said.