wireless technology, and basic construction material into a multi-modal sensor package that can report building conditions to a remote operator. The innovation could change the face of the construction industry, says Liu. "We are living with more and more smart electronics all around us, but we still live and work in fairly dumb buildings. By making our buildings smarter, we can improve both our comfort and safety." The prototype smart brick features a thermistor, two-axis accelerometer, multiplexer, transmitter, antenna, and battery. Built into a wall, the brick could monitor a building's temperature, vibration, and movement. Such information could be vital to firefighters battling a blazing skyscraper or to rescue workers ascertaining the soundness of an earthquake-damaged structure. "Our proof-of-concept brick is just one example of where you can have the sensor, signal processor, wireless communication link, and battery packaged in one compact unit," says Liu. "You also could embed the sensor circuitry in WIRELESS SMART STUFF concrete blocks, laminated beams, structural steel, and many other building materials." To extend battery life, the brick could transmit building conditions at regular intervals instead of operating continuously. The brick's battery could also be charged through the brick by an inductive coil, similar to the type used in electric toothbrushes and some artificial heart pumps. The researchers are currently using off-the-shelf components, SO there's plenty of potential for making a smaller sensor package. "Ultimately, we would like to fit everything onto one chip, and then put that chip on a piece of plastic, instead of silicon, to make it more robust," says Engel. Silicon is a rigid, brittle material, which can easily crack or break. Sensor packages built on flexible substrates would not only be more resilient, they would offer additional ver- satility. "For example, you could wrap a flexible sensor around the iron rein- forcing bars that strengthen concrete and then monitor the strain," s