Humidity sensors fabricated with photo-curable electrolyte inks using an ink-jet printing technique and their properties

Photo-curable humidity-sensitive electrolyte inks were prepared by dissolving the following in methanol/2-methoxyethanol: [2-[(methacryloyloxy)ethyl]dimethyl]propyl ammonium bromide (MEPAB), 1,5-[bis(2-methacryloxyethyl)dimethylammono]pentane dibromide (MDAPD), a multifunctional reactive oligomer (SP1013), trimethylolpropane triacrylate (TMPTA), and photo-initiators. The inks were composed of mixtures with the following contents: MEPAB/MDAPD/SP1013/TMPTA = 6/24/17.2/12.8, 10/20/17.2/12.8, 15/15/17.2/12.8, 20/10/17.2/12.8, and 24/6/17.2/12.8. The humidity-sensitive membranes were fabricated on an electrode using a wide format drop-on-demand ink-jet printer equipped with a UV lamp system, and the printed inks were UV-cured simultaneously. The humidity-sensing characteristics including water durability and high humidity–temperature cycle were measured and estimated. The humidity sensors obtained using the ink-jet print technique showed similar humidity-sensitive characteristics within ± 1%RH.