To track changing conditions in deserts, forests, oceans, or the atmosphere, environmental sensors must (just like the postman) deliver their messages through snow, rain, heat, and gloom of night. Sensors attached to bridges, roadways and other structures face similarly extreme conditions—or worse, if they need to function through hurricanes and earthquakes.

NSF-sponsored researchers are developing new sensors that can operate reliably in those environments. They’re also hard at work on sensor systems, designing and deploying networks of sensors that will bring unprecedented detail to civil and environmental monitoring.

A robotic sensor package is suspended between two treetops at the Wind River Canopy Crane Research Facility in Washington State. The instrument can move along the cable as well as up and down, providing images and precise local climate data. Credit: Center for Embedded Networked Sensing, UCLA; Wind River Canopy Crane Research Facility, University of Washington

At UCLA’s Center for Embedded Network Sensing (CENS), William Kaiser monitors delicate ecosystems in California’s San Jacinto Mountains. By networking fixed data-taking stations and mobile “infomechanical systems,” Kaiser’s research group is keeping tabs on the James Reserve, home to 50 endangered species. The group’s mobile devices travel along wires strung from tree to tree, lowering sensors to take temperature, humidity and light-level measurements at varying heights above the forest floor. Powered by solar cell-battery combinations, the devices pass along data from node to node in a network that will eventually include one hundred stations.

Center director Debra Estrin and her colleagues developed the protocols and data management techniques that let this ad hoc wireless sensor network operate where power restrictions, unstable transmission environments, and ever-changing numbers of nodes would frustrate traditional networks. These same strategies are utilized in other CENS projects, such as monitoring the nesting habitats of birds, and tracking the flow of fertilizer from farms through a sediment zone and into the Merced River.

The Rio Puerco bridge outside of Albuquerque, New Mexico, was built with embedded fiber optic sensors to monitor vibration and wear. Credit: © Smartec

Civil engineers like the New Mexico State University’s Rola Idriss envision the day when sensors embedded in bridges and roadways routinely report the first signs of unusual wear long before they’re visible to human inspectors. As with human healthcare, early detection of structural health problems allows early intervention, ultimately saving money, improving longevity, and increasing safety. Idriss and her colleagues installed 120 fiber optic sensors on a 1970s-era bridge on Interstate 10 in Las Cruces, with support from NSF and the Federal Highway Administration.

The fiber optic sensors supply the university researchers with a continual stream of data documenting the bridge’s reaction to traffic, weather, and the ravages of time. But the New Mexico team has even higher hopes for the new Rio Puerco bridge near Alberquerque, an innovative high-performance concrete design with sensors built right into its beams. Comparing the data acquired from their internal sensors throughout the bridge’s lifetime to information from standard inspection techniques will help them develop more efficient monitoring and maintenance procedures.