A rapid-response, high-sensitivity nanophase humidity sensor for respiratory monitoring

An ionic-type humidity sensor based on a plasma-deposited nanophase Si thin film was developed. Detection of relative humidity cycles between 20% and 90% was possible in ≤0.2 s with ∼5 orders of magnitude variation in conductance. Such superior performance is attributable to the unique arrayed column-void network structure and ultrafine thickness (e.g., 50 nm) of the Si film as well as to the lateral electrode configuration. Our sensor can be miniaturized, integrated with signal processing circuits, and fabricated on plastics. A crucial implementation, where our sensor would be very suitable and beneficial, is respiratory monitoring.