A building could look sturdy but in fact be near collapse. Minor earthquakes, for example, can create hidden cracks that could cause a structure to tumble during larger quakes. But what if walls could write their own bills of health?
Researchers at University of California, Berkeley think that's possible, with the assistance of a small sensor called the "Smart Dust mote." As part of the Center for Information Technology Research in the Interest of Society (CITRIS), engineering professor Steve Glaser is taking part in a collaboration to develop the Smart Dust mote.
"These sensors are actually very small computers with their own operating system, or tiny OS -- a 3,400-byte system that actually takes care of all the data acquisition and communication," Glaser explained. "These sensors talk to each other, they self-assemble their own peer-to-peer networks. If one gets destroyed, the sensors themselves find different routing or information and can actually change what the sensors do through software."
These battery-powered motes, which are matchbox-sized, have tiny, detachable chips. For example, one tiny chip serves as a two-way radio transceiver. Another chip -- potentially useful during fires -- measures temperature. There is even a satellite global positioning system chip that has a micro-controller and a full megabyte of memory.
The motes themselves are really just off-the-shelf components. It's the software that makes them special.
Glaser hooked up a sensor to his laptop computer and was able to record and measure seismic movements in real time. Each time he shook the sensor, the screen showed the seismic waves that jolted upward in response. The measurements calculated movement along the x and y axes to differentiate whether the shaking is occurred horizontally or vertically.
During earthquake-simulation tests, Smart Dust motes have been placed around critical beams and columns. The motes have provided more detailed structural data than traditional seismic accelerometers.
Glaser said he imagines that someday buildings will synthesize this data to come up with a quick synopsis of their own condition.
"This building, for example, has been shaken about a dozen times in tests so you can imagine there's a tremendous amount of information," he said, pointing to a building at the Richmond Field Station in the San Francisco Bay Area. "Personally I don't want to look at all of it... it's too much. So instead of numbers why don't we get answers? What if we get information instead of data? What if this wall computes its own behavior?"
He said he envisions a day when buildings will have a stoplight panel in front, indicating their condition. A red light would mean the building requires immediate attention, a yellow light would indicate that needed repairs could wait, a green light would indicate the building is fine. This would in turn help building owners and inspectors maintain building safety, especially during emergencies.
Traditional seismic accelerometers are costly and tricky to install. They require patching a lot of wires and preamplifiers, which cost $3,500 each, not to mention the labor in soldering the wires and maintaining the infrastructure. The total cost can run as high as $8,000.
A Smart Dust motes system, on the other hand, would cost about $1,000 and be quick and easy to install because it's wireless. With a network of sensors constantly streaming data in real time, buildings could be improved as well as updated.
Smart Dust motes are still in the manufacturing stage and will be on the market in four to six months.
