Scientists want to filter out toxic chemicals off your clothes. Scientists have designed threads that change colour when they recognise different types of gases, an advance that could help create smart materials to sniff out toxic chemicals.
Tufts University researchers showed that the threads could be read visually, or even more accurately by using a smartphone camera. This way, they can detect differences in colour due to analytes as low as 50 parts per million.
Formed into clothing, smart, gas-detecting threads could produce a reusable, washable, and affordable safety asset in medical, workplace, military and rescue environments, according to researchers.
The study illustrates the design method and its capacity to spread to a broad range of colours and exposure to complicated gas mixtures.
While not replacing the accuracy of electronic devices generally used to recognise volatile gases, the inclusion of gas detection into textiles allows an equipment-free readout, without the need for specialised training, researchers said in a statement.
It could make the technology available to a general workforce or low resource communities that can benefit from the information the textiles provide.
The study used a manganese-based colour, MnTPP, methyl red and bromothymol blue to demonstrate the concept. MnTPP and bromothymol blue can recognise ammonia while methyl red can recognise hydrogen chloride commonly released from cleaning supplies, fertiliser and chemical and materials production.
A three-step process "traps" the colour in the thread. The thread is first dropped in the colour, then treated with acetic acid, which makes the surface rougher and swells the fibre, probably providing more binding interactions between the colour and thread.
At the end, the thread is treated with polydimethylsiloxane (PDMS), which produces a flexible, physical seal around the thread and colour, which also deflects water and bars colour from leaching during washing. PDMS is gas permeable, enabling analytes to reach the optical colours.
"The dyes we used work in different ways, so we can detect gases with different chemistries," said Sameer Sonkusale, a professor at Tufts University.
The team used simple colours that recognise gases with acid or base properties.
"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," Sonkusale said.
The tested colours changed in a way that is dependent and equivalent to the concentration of the gas as measured using spectroscopic techniques.
In between the accuracy of a spectrometer and the human eye is the probability of using smartphones to read out and quantify the colour differences or understand signatures using multiple threads and colours.
"That would allow us to scale up the detection to measure many analytes at once, or to distinguish analytes with unique colourimetric signatures," said Sonkusale.