Multifunctional, flexible and mechanically resilient porous polyurea/graphene composite film

In this study, a porous polyurea/graphene platelet (GnP) composite film with high flexibility and multifunctionality was developed and investigated for strain sensing and energy storage applications. Morphology and mechanical properties were studied; tensile strength and Young's modulus were enhanced by 132% and 900%, respectively at 5 wt% GnPs. The polyurea/GnP film exhibited high sensitivity to various strains– namely, tension, compression, bending and twisting. In tensile strain, gauge factor was 1.86 and 6.26 within strain ranges of 0–30% and 30–60%, respectively. Interestingly, the film showed piezoresistive and capacitive-type strain sensor under compression load; a 33% increase in relative resistance with response time of 108 millisecond; and 22% increase in relative capacitance with response time of 92 millisecond when load of 5 kPa was applied. Furthermore, the strain sensor showed high durability and reliability over 20,000 cycles. The developed polyurea/GnP film showed a stable capacitive performance over 20,000 charge–discharge cycles. This work provides important insights for the potential of polyurea/graphene films in multifunctional sensors and flexible energy storage applications.