Piezo/active humidity sensing of CeO2/ZnO and SnO2/ZnO nanoarray nanogenerators with high response and large detecting range

• New humidity sensor is realized, and no external electric power is needed.
• New piezoelectric-humidity-sensing mechanism is established.
• The piezoelectric output of the device is extremely sensitive to the humidity.
• The detecting range is up to 5–95% RH.
• Self-powered active humidity sensor is a next generation of humidity sensors.

Piezo/active humidity sensing of CeO2/ZnO and SnO2/ZnO nanoarray nanogenerators with high response and large detecting range have been realized. The piezoelectric output of the devices under external deformation is extremely sensitive to the humidity with a very large detecting range. The piezoelectric output of the devices can act not only as a power source, but also as a response signal to the relative humidity of the ambience. Such behavior can be attributed to the piezotronic effect of ZnO nanowires and the surface modification of CeO2 or SnO2 nanoparticles. Our study can open a new way for actively detecting humidity in the environment.