A BP neural network based on the DE algorithm has been established to study the electrical properties of flexible Ag/PAA composites.

Humidity sensors are indispensable for various electronic systems and instrumentations. To develop a new humidity sensing mechanism is the key for the next generation of sensor technology. In this work, a novel flexible paper-based current humidity sensor is proposed. The developed alternating current electroluminescent devices (ACEL) consist of the electroless plating Ni on filter paper and silver nanowires (AgNWs) as the bottom and upper electrodes, and ZnS:Cu as the phosphor layer, respectively. The proposed humidity sensor is based on ACEL with the paper substrate and the ZnS:Cu phosphor layer as the humidity sensing element. The moisture effect on the optical properties of ACELs has been studied firstly. Then, the processing parameters of the paper-based ACELs such as electroless plated bottom electrode and spin-coated phosphor layer as a function of the humidity-sensitive characteristics are investigated. The sensing mechanism of the proposed sensor has been elucidated based on the Q~V analysis. The sensor exhibits an excellent linearity (R2=0.99965) within the humidity range from 20% to 90% relative humidity (RH) and shows excellent flexibility. We also demonstrate its potential application in postharvest preservation where the EL light is used for preservation and the humidity can be monitored simultaneously through the current.

An easy-to-fabricate, high-performance, and ultrabendable heater is always essential for the development of flexible devices such as gas sensors. Currently, most of the flexible heaters involve vacuum facilities or special inkjet printers/inks, which leads to complex processes and high fabrication cost. In this work, an innovative polymeric metalization technique was developed on polyimide substrate: in addition to the tunable electrical properties, Ag thin films obtained through the low-temperature solution-based process, the so-called surface modification and ion exchange (SMIE) process, could provide enhanced interfacial adhesion and mechanical stability. With a carbon ink as a masking layer, generated by a common home-/office-use inkjet printer, more than 400 patterned flexible heaters can be batch-fabricated on an A4 size polyimide conveniently. The results indicate that the heaters exhibit good electrical properties as well as superior bending stabilities. For the heaters with dimension of 1 cm × 1 cm, under an applied voltage of 20 Vdc, the maximum temperature achieved is 300 °C. Both the response time and recovery time are less than 15 s. The heaters can bear more than 1200 times bending cycling with a relative resistance change ratio of 0.11%. The developed technology is compatible with current batch fabrication processes such as roll-to-roll and can be employed to develop flexible heaters with high mechanical stability in the future.

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