Facilitating Response/Recovery of cellulosic humidity sensor by Densificating fibril Arrays

Hydrophilic cellulosic materials exhibit extraordinary effectiveness on sensitivity of humidity. However, the fibril network in fiber walls hinders both permeability and desorption of water, resulting in to weak their responsiveness and recoverability to humidity. Here, structural optimization is achieved by modulating interfacial bonding, resulting in an unprecedented increment in the response-recovery speed of cellulosic humidity sensors. Precisely, hydrolyzable thiol silane is introduced between cellulose nanofibers and carbon nanotubes for a covalent interface, which promotes a dense structure under evaporation induction (76.33 % reduction in thickness), avoiding the deep penetration of water. In addition, Cs 2 SnCl 6 perovskites are loaded by means of strong coordination to boost the chemical dissociation of water molecules, further enhancing the responsiveness and sensitivity of devices. The as-prepared sensor exhibits excellent response/recovery speed (1.8 s / 2.9 s) between 11 % RH to 95 % RH, which is ahead of cellulosic humidity sensors developed in the past three years, as well as satisfactory sensitivity (5.35 × 10 6 %), hysteresis (< 1 % RH), and stability (over 90 days). For application purposes, skin moisture, breathing patterns, and word syllables can be accurately identified. Moreover, it can monitor respiratory rate and amplitude stably during long-term exercise, indicating remarkable potential in human physiological humidity monitoring.