With the arrival of the Internet
of Things and artificial
intelligence,
humidity sensors monitoring water emissions from human metabolism
have attracted great attention in the fields of smart wearable devices
and noncontact human–machine interaction. However, their application
is seriously limited by the trade-off between the sensitivity and
response speed for traditional humidity sensors. Herein, to overcome
it, a self-powered high performance humidity sensor is developed on
the basis of the electric-poled and oxygen vacancy-rich BiFeO3 (BFO) ferroelectric material. The synergistic effect of ferroelectric
polarization and oxygen vacancy provides a strong driving force and
active adsorption sites for an abundance of OH/H2O adsorption,
resulting in an ultrahigh response (∼104) and ultrafast
response/recovery speed (∼84/376 ms). Benefiting from its promising
advantages, the wearable humidity sensor can accurately record the
respiration rate/depth and recognize different human respiratory behaviors
in real-time. Importantly, by utilizing the moisture from mouth-blowing
and skin, the sensors are successfully applied to noncontact control
of a robotic car, noncontact switch, and noncontact interface for
visualization applications. This work provides an effective strategy
for developing excellent humidity sensors that meet the requirement
of noncontact interaction for next-generation intelligent electronics.