Engineering Minute

Engineering Minute – Color Changing Threads Detect Gases

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Tufts University engineers have developed a method for fabricating special dyed threads that change color when they detect different gasses. The color change can be detected both visually and with a smartphone camera for enhanced accuracy. The threads could be woven into clothing worn by the military or first responders as a way to warn the wearers if they are around a dangerous chemical. A study regarding how the threads work was recently published in Scientific Reports

Sensing threads prepared with bromothymol blue (top thread), methyl red (middle thread) and MnTPP (bottom thread) are exposed to ammonia at 0 ppm (left panel) 50 ppm (middle panel) and 1000 ppm (right panel).
Sensing threads prepared with bromothymol blue (top thread), methyl red (middle thread) and MnTPP (bottom thread) are exposed to ammonia at 0 ppm (left panel) 50 ppm (middle panel) and 1000 ppm (right panel).
Credit: Tufts University

 

“The dyes we used work in different ways, so we can detect gases with different chemistries,” says Sameer Sonkusale, professor of electrical and computer engineering at Tufts University’s School of Engineering. “But since we are using a method that effectively traps the dye to the thread, rather than relying so much on binding chemistry, we have more flexibility to use dyes with a wide range of functional chemistries to detect different types of gases,”

 

From the Tufts University article: "The study used a manganese-based dye, MnTPP, methyl red, and bromothymol blue to prove the concept. MnTPP and bromothymol blue can detect ammonia while methyl red can detect hydrogen chloride - gases commonly released from cleaning supplies, fertilizer and chemical and materials production. A three-step process “traps” the dye in the thread. The thread is first dipped in the dye, then treated with acetic acid, which makes the surface coarser and swells the fiber, possibly allowing more binding interactions between the dye and tread. Finally, the thread is treated with polydimethylsiloxane (PDMS), which creates a flexible, physical seal around the thread and dye, which also repels water and prevents dye from leaching during washing. Importantly, the PDMS is also gas permeable, allowing the analytes to reach the optical dyes."

 

Read more about the color changing threads that detect gasses at Tufts University.