The mood ring, a popular fad in the late 1970s, is a specialized liquid crystal thermometer typically ornamented with a faux gemstone (usually made of quartz or glass). Temperature changes in the wearer’s finger cause the crystal to reflect different wavelengths of light, which change the color of the stone. Green is considered normal or average, while blue is calm and relaxed and black is stressed and tense.
Fast forward to 2016 and Vanderbilt University in Nashville, where a similar sensing technology has been developed by researchers at the school’s Laboratory for Systems Integrity and Reliability. This new smart sensing material changes color when it is damaged or about to fail, giving the engineering community a potential cost-effective means to detect minor infrastructure deficiencies before they become critical. The Nashville researchers are incorporating fluorescent nanoparticles into the material itself as a detection system that illuminates tiny cracks before they lead to major structural failures. Their unique type of nanoparticle, called a white light quantum dot, emits white light where other quantum dots only emit light at specific wavelengths.
Preliminary tests have been promising. The strength of the quantum dot emissions has been found to correlate to the level of stress that the material experiences. This is good news, considering that the American Society of Civil Engineers’ 2013 report card on the nation’s infrastructure received a D+ grade point average. ASCE estimates that we will need to invest more than $3 trillion by 2020 to raise this grade. While challenges remain (for example, the quantum dots seem to lose their fluorescence when exposed to light), the ability to detect minute fractures has the potential to save not just money, but lives.
To understand more about this fascinating “new kind of strain gauge,” view Vanderbilt University Mood Ring Technology.