Smart humidity sensor of graphene enhanced superabsorbent

It is well known that some polymers change their chemical, physical and mechanical properties, for example electrical resistance, capacity, size and shape in response to environmental stimuli through the absorption and desorption process of water. These changes can be converted into an electric signal which in turn can be used to monitor changes of the surrounding environment. In this study, we utilize superabsorbent polymer that can absorb and retain extremely large amounts of liquid relative to its own mass, with graphene to construct a moisture sensor. This moisture sensitive material and graphene can form hybrid hydrogels and after freeze-dried, they formed porous structures. The hybrid composites are excellent materials for high-resolution humidity sensing. The increased transduction is caused by the change in the effective electrical conductivity, which is governed by the varying percentages of air and water within the graphene/superabsorbent sensor. The change in the effective dielectric value will cause a measured change in conductivity that is proportional to the change in water absorbing.