Summary

Commercial sensors are mainly based on metal oxides, polymers and porous silicon. They are cheap and have good repeatability within a certain humidity range, but show some disadvantages in terms of post-maintenance and interference from external factors.

As the market demand is huge and there are gaps in demand, the choice of specific materials has to be carefully considered. The use of pyrolysis to extract carbon powder from biological materials such as silk as a sensing material is a novel and promising option. The advantages of biomass carbon materials include sustainability, greenness, cheapness, large specific surface area, high heteroatomic and high biocompatibility.

The whole experiment is based on a humidity chamber and a universal electricity meter. The experimental route is mainly to obtain humidity-time curves. The experiment is repeated for three rounds for each sample to exclude chance.

Three sets of samples were carbonised at different high temperatures (450°C, 600°C, 750°C). The 600 degree sample is an excellent material for a humidity sensor, as it not only responds quickly but also keeps stable at constant humidity. 450 degree samples can also be used as a sensing material, but the resistance jitters at constant humidity. 750 degree samples show an unusual increase in resistance with increasing humidity, which is worth further investigation.