Biomass confined gradient porous Janus bacterial cellulose film integrating enhanced radiative cooling with perspiration-wicking for efficient thermal management.

Sophisticated structure design and multi-step manufacturing processes for balancing spectra-selective optical property and the necessary applicable performance for human thermal-wet regulation, is the major limitation in wide application of radiative cooling materials. Herein, we proposed a biomass confinement strategy to a gradient porous Janus cellulose film for enhanced optical performance without compromising thermal-wet comfortable. The bacterial cellulose confined grow in the micro-nano pores between PP nonwoven fabric and SiO achieving the cross-scale gradient porous Janus structure. This structure enables the inorganic scatterers even distribution forming multi-reflecting optical mechanism, thereby, gradient porous Janus film demonstrates a reflectivity of 93.1 % and emissivity of 88.1 %, attains a sub-ambient cooling temperature difference of 2.8 °C(daytime) and 8.5 °C(night). Film enables bare skin to avoid overheating by 7.7 °C compared to cotton fabric. It reaches a 17.2 °C building cooling temperature under 1 sun radiance. Moreover, biomass confined micro-nano gradient porous structure integrating with Janus wet gradient guarantees the driven force for directional water transportation, which satisfies the thermal-wet comfortable demands for human cooling application without any further complicated process. Overall, bacterial cellulose based biomass confining strategy provides a prospective method to obtain outdoor-service performance in cooling materials.