text-only page produced automatically by LIFT Text Transcoder Skip all navigation and go to page contentSkip top navigation and go to directorate navigationSkip top navigation and go to page navigation
National Science Foundation
Sensor Tech
Out In The Field
Sensor Apps
Environment & Civil
Industry & Commerce
Safety & Security
Classroom Resources
Glass fibers...

These glass fibers are flexible and rugged sensors for neutrons and gamma radiation with applications in national security, medicine, and materials research.

Credit: Pacific Northwest National Laboratory

Sensor Applications: Safety & Security

Fire fighters...
A network of sensors is deployed in a burning building. They create temperature maps that allow fire fighters to move through the space safely.

Credit: Ron Peterson, Computer Science Department, Dartmouth College
Household smoke and carbon monoxide detectors are commonplace. Motion-triggered floodlights illuminate driveways and parking lots. Metal detectors and biohazard monitors guard ports and transportation hubs. Spill sensors protect factory workers from hazardous chemicals. The safety and security of our homes, public spaces, and workplaces rests on sensing danger and issuing timely warnings. New sensing technologies developed with NSF funding, and new methods for gathering and processing data from distributed sensor systems, support a national effort to enhance capabilities for reliably and accurately evaluating situations that threaten our wellbeing.

Nanotech Sensors

Click to view sensor animations.
Click on the micro-cantilevers to see how these molecular recognition sensors work, and view other sensor animations.

Credit: Nicolle Rager, National Science Foundation
At Northwestern University’s Nanoscale Science & Engineering Center (NSEC) for Integrated Nanopatterning and Detection Technologies, chemist and Center director Chad Mirkin uses dip-pen lithography to deposit “lock” biomolecules on silicon substrates. Mirkin and his coworkers write molecular patterns only a few nanometers wide, and then expose the decorated substrates to solutions containing “key” molecules. They are able to observe binding between pairs of complementary molecules with both exquisite sensitivity and high specificity. Sensors based on technologies like this will be able to detect hazardous substances in minute quantities, but false alarms will be a rarity. And the same sensor framework could be adapted to detect different substances just by changing the molecular “ink” with which the patterns are written.

Another chemist who applies the nanotechnologist’s perspective to sensor development is Robert Hamers at the University of Wisconsin-Madison. Hamers also uses a molecular lock and key approach—for example, he’s worked with the binding of biotin (vitamin B-7) to the small protein avidin. Hamers has developed methods for attaching biotin to diamond films and electrically probing for the partner protein. He has used similar techniques to detect specific DNA fragments. The rugged diamond-film devices can be reliably and repeatably cycled, and the radio frequency measurements that signal the presence or absence of the complementary molecules lend themselves to integration in a sensor chip.

Artificial Nose

Click to view sensor animations.
Click on the rose to see how polymers can sense smells and view other sensor animations.

Credit: Nicolle Rager, National Science Foundation
Nate Lewis’s work exemplifies a different approach to sensing chemical or biological agents. Lewis’s technique uses an array of sensors, each of which senses not one highly specific molecule, but a group of related compounds. Using computational techniques to combine the signals from several different sensors and compare the results to known responses, he’s created an artificial nose that can sniff out trace quantities of a variety of chemicals.

Lab on a Wrist

The Center for Wireless Integrated Microsystems (WIMS), an NSF Engineering Research Center directed by microelectromechanical systems pioneer Kensall Wise, is putting together all the pieces needed to make networkable, wristwatch-sized chemical analyzers. Scientists and engineers from the University of Michigan, Michigan Technical University, and Michigan State University participate in the ERC, designing sensors, pumps, low-power microprocessors, and radio-frequency componentry for the miniature instruments.

Close-up of a wristwatch-sized chemical analyzer.
This electron micrograph shows the center of a meter-long capillary tube etched into a silicon wafer. In gas chromatography, different gasses separate as they traverse long, narrow capillary columns.

Credit: NSF Engineering Research Center for Wireless Integrated MiicroSystems, University of Michigan
While the WIMS’s work will ultimately become part of many different types of sensor and monitoring systems, they’re concentrating current efforts on two testbeds:  a cochlear implant and an environmental monitoring system. Ted Zellers from the University of Michigan’s School of Public Health heads the team designing the monitoring testbed, a microscale chromatograph that could detect hazardous gases equally well in homeland security applications or industrial process control. To shrink this chemical analysis workhorse down to 1 cubic centimeter, Zellers, Wise, and their students wrap meter-long, 100 micron-wide chromatography columns into tight spirals. They design and fabricate microscopic pumps, valves, and injectors to capture sample gasses and transport them through the instrument. They build electronic circuitry that generates all necessary voltages from batteries, and transmits data via integrated micromachined antennas and radiofrequency circuitry. Size and power consumption must be minimized without compromising performance.

The Sensor Revolution A Special Report