Dramatically enhanced strain- and moisture-sensitivity of bioinspired fragmentized carbon architectures regulated by cellulose nanocrystals

Although flexible conductive polymeric sensors responding to different stimulus have been extensively explored, it remains challenge to integrate high multi-stimuli sensitivity into one material. Herein, novel electromechanical sensors were fabricated, exhibiting dramatically enhanced strain- and water/moisture-sensitivity. The hybridized nano carbons of graphene and carbon nanotubes (CNTs) were regulated with cellulose nanocrystals (CNCs), followed by embedding into the polymeric elastomer via transfer process. The CNCs not only fragmentized the electromechanical networks under external stress, but also amplified the swelling effect on the conductivity variation as exposed upon water/moisture due to the mechanical reinforcement and amphiphilic nature. Micro/nano cracks were generated on the conductive surface layer, enabling dramatic enhancement on the sensitivity and reversibility in the strain sensing. The gauge factor was up to 1129 within 20% of the strain, which was higher by 182 times compared to that of the control sample without the CNCs content. Moreover, the electromechanical sensors improved the water/moisture sensing whose sensitivity was enhanced by 65 times due to the micro/nano cracks in the fragmentized carbon architecture. The findings extend the application of natural cellulose to exploit multi-stimuli responsive electronics and provide a facial strategy to optimize the sensory performance, which may greatly benefit the developments of the flexible and wearable electronics.