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

Moisture in environment can severely decrease the contact charging property of polymers, which usually reduces the output of the 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 high humidity environment with high output performance. The surface of the PET film is modified by β-cyclodextrin through molecular self-assembly to introduce hydroxyl groups, which increases the ability to form hydrogen bonds with water molecules in high humidity environment, immobilizing water molecules to participate in contact charging. Since water molecule is 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 TENG. Different from PET film-based TENG without hydroxyl on the surface, the electrical output of β-cyclodextrin-modified PET-based TENG increases with the increase of environmental humidity. The circuit current (Isc) of the TENG increases from 3.7μA to 16μA when the humidity increases from 15% to 95%. Moreover, the dielectric property of the PET film increases due to the introduction of amino groups in β-cyclodextrin, which causes the Isc of TENG to increase by 3.7 times at 15% RH. This strategy highly expands application scopes of TENGs for energy harvesting and self-powered sensors in high humidity environment, especially in cloudy, foggy days or under water and sweat conditions.