A simple and fast responsive colorimetric moisture sensor based on symmetrical conjugated polymer

[Display omitted] •A rapid blue to red colorimetric moisture sensor based on conjugated polymer.•Spin-coating film shows colorimetric response to atmospheric humidity (RH = ∼80 %).•Inkjet-printed image exhibits ultrafast sensing to moisture in a fraction of a second.•Colorimetric moisture sensor was used for application in inkless writing.•Smart epoxy paint incorporated with PDA was developed to sense moisture. This work describes a colorimetric moisture sensor based on conjugated polydiacetylene for humidity/moisture with a rapid blue to red colorimetric response. The moisture responsive material is incorporated into the polymer film, printing ink and epoxy paint. The polymer based film shows weak colorimetric response to atmospheric humidity (RH = ∼80 %) at temperatures up to 45 °C starts within 30 s, whereas the paper based inkjet-printed image exhibits ultrafast sensing to moisture in a fraction of a second. Test results indicated that this colorimetric sensor can detect relative humidity, especially at values higher than 80 % in an irreversible manner. Moreover, a smart epoxy paint embedded with poly(DCDA-HC2) can also sense the moisture suggests its tremendous potential advantage application as a colorimetric moisture sensor.