October 15, 2010
Column | Korky Koroluk
Nanotechnology advancing quickly
The science of the very small — nanotechnology — is advancing so quickly that it’s hard to keep up. Just pause for breath for a few minutes and you find you’re a week behind in your reading.
Suddenly, you find it hard to figure out how everything fits together into a coherent, useful tool that’s of use in the architecture-engineering-contracting industry.
So it was nice to find a feasibility study on inexpensive wireless sensors based on nanotechnology published recently in the International Journal of Materials and Structural Integrity.
Can these tiny sensors do the job? In a word, yes. And the need for them is great, say the report’s authors.
The study brought together scientists from several universities in the United States and Tunisia, under the leadership to Mohammed Saafi, of the department of construction engineering and management at North Dakota State University.
He points out in the paper that civil structures are prone to continuous and uncontrollable damage during their design life. It might be weather damage, aging of materials, earth tremors or lack of maintenance.
So, he says, a continuous monitoring system is needed to improve safety. A trivial problem, like small cracks and fissures, can be easily turn into a big problem.
The answer, the researchers found, could be nanotechnology and wireless systems. Such systems are already used in a wide range of fields including transportation, communications and medicine, as well as in a number of military applications. Their use in civil engineering, however, is newer, and offers great potential for improved monitoring and management of structures.
The researchers developed and evaluated two types of wireless devices for remote monitoring of concrete structures. They are sensors based on microelectromechanical systems, or MEMS, and were designed to monitor temperature and moisture within the concrete. Long-gauge nanotube sensors were employed for crack detection.
“If designed properly, wireless MEMS and nanotechnology-based sensors could be used as embedded components to form self-sensing concrete structures,” Saafi wrote. Such sensors would gather and transmit information about the health of a structure by detecting the early formation of tiny cracks and measuring such key elements as temperature, moisture, chloride, acidity and carbon dioxide levels — any or all of which might be factors in decreasing structural integrity.
And that, the scientists say, would allow owners to make critical decisions about operation, maintenance, repair and replacement.
In Canada, researchers are also concerned with ways to use high-tech monitoring devices and techniques. It’s called the Intelligent Sensing for Innovative Structures Canada Research Network, or ISIS. It’s based at the University of Manitoba but includes researchers from 15 Canadian universities.
The group has done a lot of work on wired and wireless sensors to monitor bridges and has designed some itself. They’ve even coined the word “civionics” to describe what it is the sensors do, which is to provide a way to monitor a structure’s health.
Data about Canada’s bridges are still somewhat limited, but in the U.S. about 20,000 bridges are considered structurally deficient, meaning they can’t carry the loads they were designed for. So it’s a big problem, with the potential to get much, much bigger.
Despite that, sensors have not yet been widely adopted, although that’s improving year by year. And as sensors allow engineers to watch how a structure performs, they will not only be able to save on repairs, but use the performance data to fine-tune both designs and materials.
Korky Koroluk is an Ottawa-based freelance writer. Send comments to firstname.lastname@example.org
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