Kraft lignin-based piezoresistive sensors: Effect of chemical structure on the microstructure of ultrathin carbon fibers

In an attempt to diversify lignin applications, in this study, electrospun mats composed of ultrathin carbon fibers from Eucalyptus globulus Lignin (EKL) and sugarcane bagasse Kraft lignin (BKL) capable of detecting certain human body motions were fabricated and their chemical structures fully investigated accordingly. Results suggested that the main chemical structure of EKL was slightly linear with sinapyl alcohol and coniferyl alcohol as the basic units and pinoresinol, arylglycerol-β-aryl ether, phenylcoumaran, with diphenylethane as the main linkages. The slightly linear EKL and cross-linked BKL tended to form amorphous carbon and graphite crystallites under the same heat treatment process respectively, thereby resulting in a large difference in the resistance of fabricated sensors. The amplitude of signals due to changes in the relative resistance (△R/R0) for EKL ultrathin carbon fiber (CF)-based sensor was approximately 9 × 104 during the finger bending process, while large (△R/R0 ~380) and small (△R/R0 < 10) relative resistance variations due to BKL-CF-based sensors were detected during the arm bending and finger pressing motions respectively.