All-printed flexible self-powered humidity sensor

Existing humidity sensors are often large in size and complex in structure due to the limitations of the power supply form. Traditional self-powered humidity sensor devices also often require complex preparation processes or have a narrow humidity response range and a low maximum voltage response, which significantly limits their application range. Herein, a paper-based fully printed flexible self-powered humidity sensor (FSHS), based on electrochemical principles, is proposed for the first time. This innovative sensor, combined with conventional screen-printing technology, enables the integration of low-cost, customizable, 2D, and non-contact humidity sensing devices. The anode ink, cathode ink, and sensing layer are printed on the paper as planar interdigital electrodes to form a FSHS with self-powered and humidity sensing functions. This sensor features a simple preparation process, a wide response range (11%-95% RH), ultra-high voltage response (1.03 V), excellent long-term stability, rapid response/recovery times, and excellent linearity between voltage response and humidity. It demonstrates exceptional flexibility, with virtually no change in voltage under extreme bending conditions. Additionally, this FSHS can be made into various shapes/patterns, making it ideal for wearable respiratory detection devices, non-contact buttons, and energy storage in specialized circumstances.