A β-cyclodextrin enhanced polyethylene terephthalate film with improved contact charging ability in a high humidity environment

Moisture in the environment can severely decrease the contact charging properties of polymers, which usually reduce the output of solid–solid triboelectric nanogenerators (TENGs), hindering their further practical applications. To solve this problem, in this paper we fabricated a new type of polyethylene terephthalate (PET) based TENG, which can work stably in a high humidity environment with high output performance. The surface of the PET film is modified with β-cyclodextrin to introduce hydroxyl groups, which increase the ability to form hydrogen bonds with water molecules in a high humidity environment, immobilizing water molecules to participate in contact charging. Since water molecules are a more positive material, the PET film combined with water molecules will acquire more positive charges during the contact charging process, which will greatly increase the electrical output of PET-based TENGs. Different from the PET film-based TENG without hydroxyl on the surface, the electrical output of the β-cyclodextrin-modified PET-based TENG increases with the increase of environmental humidity. The circuit current (I(sc)) of the TENG increases from 3.7 μA to 16 μA when the humidity increases from 15% to 95%. Moreover, the dielectric properties of the PET film increase due to the introduction of amino groups in β-cyclodextrin, which causes the I(sc) of the TENG to increase by 3.7 times at 15% RH. This strategy highly expands the application scope of TENGs for energy harvesting and self-powered sensors in high humidity environments, especially in cloudy and foggy days or under water and sweat conditions.