Inexpensive wireless sensors based on nanotechnology could be used to alert engineers to problematic damage to buildings, bridges, and other structures before they become critical, according to a study in the Journal of Materials and Structural Integrity.

As a proof of concept, researchers have developed and evaluated two types of wireless devices for the remote monitoring of concrete structures. The devices are sensors based on microelectromechanical systems, MEMS, and were designed to monitor temperature and moisture within concrete.

Long gauge nanotube sensors were employed for crack detection in the feasibility study. MEMS and nanosensors have already been used in a wide range of engineering and science fields such as transportation, communication, military and medicine. Their use in civil engineering is a new application with great potential.

"If designed properly, wireless MEMS and nanotechnology-based sensors could be used as embedded components to form self-sensing concrete structures," the study's authors explains. Such devices would gather and transmit information about the health of a structure by detecting the early formation of tiny cracks and measuring the rate of key parameters, such as temperature, moisture, chloride, acidity and carbon dioxide levels each of which might reflect a decrease in structural integrity.

Civil structures are prone to continuous and uncontrollable damage processes during their designed service lifespan. These damaging processes might be due to weather, aging of materials, earth tremors, and a lack of maintenance.

A continuous monitoring system is needed to improve safety. Unfortunately, the costs and required time expenditure often mean monitoring is not carried out in a timely manner and trivial problems, such as small cracks and fissures, ultimately become serious conditions that threaten the integrity of a structure.

"Information obtained from [nanotechnology-based] monitoring techniques would allow the
owners to make critical decisions regarding operation, maintenance,
repair and replacement under financial constraints," the team says.

Citation: Saafi et al., 'Wireless and embedded nanotechnology-based systems for structural integrity monitoring of civil structures: a feasibility study', April 2010, 4(1), 1 - 24; doi:10.1504/IJMSI.2010.032494