Researchers at Tufts University claim to have developed a novel method of producing water repellent dyed textiles capable of changing colour in the presence of a variety of gases. A number of dyes have been utilised, changes to the colours of which represent an interaction with a potentially hazardous gas. It’s thought this novel fabrication method could be leveraged by the military, in industrial workplaces and in the medical sector to provide a visual guide of exposure levels. The team has reiterated that while this method shouldn’t replace the use of electronic devices that similarly detect volatile gases, dyed threads could provide a cost-effective solution to monitoring the levels of a gas found in an environment.

Manganese-based dyes, MnTPP, methyl red, and bromothymol blue were first used to prove the efficacy of the concept. MnTPP and bromothymol blue can detect ammonia while methyl red can detect hydrogen chloride – gases commonly released from cleaning supplies, fertiliser, chemical and materials production. “The dyes we used work in different ways, so we can detect gases with different chemistries,” said 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,” he said.

A three-step process enables the research team to yield the reactive dyed threads. The textile is first dipped in the chosen dye before it is treated with acetic acid, which makes the surface coarser and swells the fibre, enabling further binding interactions between the dye and thread. Finally, the thread is treated with polydimethylsiloxane (PDMS), which creates a flexible, physical seal around the thread and dye. The PDMS treatment is water repellent but gas permeable, which lends itself to commercial applications in which it must retain its sensitivity to gases but be washable. According to the Tufts team the dyes change colour when affected by as little as 50 analytes per million. Spectroscopic methods can be used to detail the true effects and volume of a gas in an environment. A more accessible device, a smartphone, can also be used to contextualise any colour signatures.

While still at a proof-of-concept stage, the research has led to the inception of an efficient, cost-effective and washable solution. The latter of which is often a stumbling block for work on smart textiles. The scope of the innovation could also be broadened and tailored to specific fields where exposure to chemicals may be somewhat of a threat.