Did you know of dyed threads that can change colour when they detect a variety of gases? Well not till now. But recent invention of a new fabrication method by the engineers of Tufts University, Medford has made us all know about one such thing.
These threads can be visually read and seen precisely by a smartphone camera for detecting changes of colour due to analytes as low as 50 parts per million. These smart, gas-detecting threads can lend a reusable, washable and affordable safety asset in medical, workplace, military and rescue environments. Without the requirement for specialized training, the method of instilling in the gas detection into textiles enables an equipment-free readout. This can make the technology accessible to a general workforce and even to the low resource communities that can benefit from the information provided by the textiles.
Manganese-based dye, MnTPP, methyl red and bromothymol blue have been used in this study. Ammonia can be detected by MnTPP and bromothymol blue while hydrogen chloride can be detected by methyl red. Ammonia and hydrogen chloride are few gases releasd commonly from cleaning supplies, fertilizer and chemical and materials production.
The dye is trapped in the thread by a three-step proces, where in the first step, the thread is dipped in the dye and then treated with acetic acid that makes the surface coarser and swells the fiber. At last, the thread is treated with polydimethylsiloxane (PDMS) that creates a flexible, physical seal around the thread and dye. This seal repels water and prevents dye from leaching during washing.
The way of changing of colour by the tested dyes depends proportionally to the concentration of the gas as measured using spectroscopic methods. Smartphones can be used to read out and quantify the colour changes or interpret colour signatures using multiple threads and dyes.
Dissolved ammonia can also be detected by working the fabric under water. The PDMS sealant is hydrophobic and keeps water away from the thread and so the disolved gases can reach the dye to be quantified. These smart fabrics can detect carbon dioxide or other volatile organic compounds during oil and gas exploration as one possible application. The fabric can also be used for consistent quantifiable detection many times over as the dye can't be diluted due to repeated washing.
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