A Flexible Humidity and Temperature Sensor Based on Calligraphy Itself for Calligraphy Conservation Application

Calligraphy preservation requires strict humidity and temperature environment, however, there are feeling differences between calligraphy and currently used sensors. Herein, a novel strategy is proposed to employ calligraphy itself (composed of paper and carbonic ink) as a sensor instead of sensitive components based on metals or semiconductors to eliminate sensing deviations. Carbonic ink can be decorated on paper substrate through dip coating or hand writing and the as-prepared composite calligraphy (CIP) is served as multifunctional sensor for humidity and temperature monitoring. The CIP demonstrates an admirable sensitivity to water molecules, showing a high humidity sensitivity of 506.36%/RH in the range of 94–100%RH and liquid water sensitivity of 17,680%. A linear negative temperature coefficient dependence of CIP as a temperature sensor is observed, and it exhibits outstanding performances including admirable temperature sensitivity of −3.13%/°C and prominent stability. As a result, CIP with accurate humidity and temperature sensing capability based on carbonic ink and paper as sensing element and flexible substrate shows brilliant possibility in calligraphy conservation.