Numerous emerging applications require precise monitoring
of humidity
that is not only sensitive and miniaturized but also durable and portable.
However, except for the existing sensing mechanisms, such as resistive,
capacitive, impedance, and voltage-based devices, little attention
has been paid to exploiting dual readout modes with novel properties
that can meet the requirements of simplicity and convenience. In this
work, an example of color/fluorescence dual-switching by using an
aggregator building block of naphthalenediimide with a porous hygroscopic
polymer matrix is proposed. With an increase in the water fraction,
there are obvious variations in fluorescence, driven by H-aggregation
of the aggregator, and in color, driven by intramolecular-charge transfer,
which facilitate the monitoring of external humidity. More importantly,
the prepared humidity-sensitive switch demonstrated excellent cycling
stability and reversibility. This work may shed light on the precise
fabrication of aggregation-activated materials for potential applications
in humidity-sensitive systems and switching devices.