Humidity sensing properties of surface functionalised polyethylene and polypropylene films

The use of different types of surface modified polymers such as polyethylene (PE) and polypropylene (PP) as humidity sensors has been investigated. Some of these surface functionalised polymers after controlled sulphonation have promising humidity-dependent resistance changes (109–106 Ω with a change in the relative humidity (RH) from 30 to 95%) and also other favourable characteristics such as linearity and short response time. A systematic study of the humidity sensing behaviour with and without different types of surface functionalisation (sulphonation, lithiation and gold nanoclusters attachment) reveals that the sensitivity is controlled by surface structure and the extent of functionalisation, causing a change in carrier concentration and the mobility of protons and counter ions.