Rachel Owyeung and colleagues, Tufts University, Medford, MA, USA, have developed a fabrication method to create dyed threads that change color when they detect a variety of gases. The dyes in the threads change color in a way that is dependent and proportional to the concentration of the gas The threads can be read visually, or more precisely, by use of a smartphone camera. They detect analytes as low as 50 parts per million.
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. This repels water and prevents the dye from leaching during washing but is gas permeable and allows the analytes to reach the optical dyes.
The method can use various dyes such as acidic, basic, and metalloporphyrin dyes. The team tested the manganese-based dye, MnTPP, methyl red, and bromothymol blue. MnTPP and bromothymol blue can detect ammonia. Methyl red can detect hydrogen chloride, e.g., released from cleaning supplies and fertilizer.
Woven into clothing, smart, gas-detecting threads could provide a reusable, washable, and affordable safety asset in medical, workplace, military and rescue environments.
- Colorimetric Gas Sensing Washable Threads for Smart Textiles,
R. E. Owyeung, M. J. Panzer, S. R. Sonkusale,
Scientific Reports 2019.