Mixing fluorescent nanoparticles and clear polymer resin yields a novel sensor that changes optical properties under stress.

This “mood ring” could comprise part of a cost-effective smart system for monitoring the condition of bridges and other structures.

This “mood ring” could comprise part of a cost-effective smart system for monitoring the condition of bridges and other structures.This “mood ring” could comprise part of a cost-effective smart system for monitoring the condition of bridges and other structures.A team from Vanderbilt University’s Laboratory for Systems Integrity and Reliability (LASIR) reports that adding a tiny concentration (1-5%) of specialty nanoparticles to the matrix produces a characteristic light signature as the material endures different levels of stress.

Conventional methods for monitoring structural conditions rely on physical inspection or networks of physical sensors. High costs, including manpower and data processing, currently limit deployment of these methods. Researchers say that their alternative method can overcome these limitations in a range of applications.

The research is an outgrowth of work by Vanderbilt chemist Sandra Rosenthal, who in 2005 accidentally discovered the nanoparticle called a white quantum dot while attempting to create the smallest cadmium selenide quantum dot possible. Doug Adams, director of LASIR, later realized that these quantum dots are tailor-made for smart materials.

Initial tests indicate that the dot’s emission spectrum decreases as load increases. The mechanism remains an area for further research.

Adams and his team have a number of hurdles to overcome before developing real-world applications of their discovery. For example, in some tests, the spectrum that was emitted increased rather than decreased under stress.

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