A highly fast capacitive-type humidity sensor using percolating carbon nanotube films as a porous electrode material

Open porous multi-walled carbon nanotube (MWCNT) film networks were used as an upper electrode of polyimide (PI)-based capacitive humidity sensor for highly fast response time. MWCNT films were deposited by spray-dry method and patterned by O
₂
plasma. PI capacitive humidity sensors with MWCNT film electrodes showed a very short response time of less than 3 s and a good linearity of 0.9995 compared to the humidity sensors with porous Cr electrodes. The large improvement in response time was explained on the base of a percolated pore network that is more accessible for water molecules.