Fresh water scarcity becomes a crisis to human survival and development. Atmospheric water capture with remarkable advantages such as energy-independence, low-cost, etc., has been supposed as a promising way to...

Novel hydrophobic/hydrophilic Janus fibrous membranes, the poly[4,4 -methylenebis (phenylisocyanate)-alt-1,4-butanediol/di(propylene glycol)/plycaprolactone] (PU) fibrous membrane as the hydrophobic layer and cellulose acetate (CA) fibrous membrane as the hydrophilic layer, were fabricated by the so-called "layer-by-layer" electrospinning technology. A series of the PU/CA Janus membranes with different electrospinning time of the CA layers by which the thickness of hydrophilic layer can be controlled were also prepared to uncover its influence on the directional water vapor transmission. The results showed that water vapor transmission capability from the hydrophobic side to the hydrophilic side of the PU/CA Janus fibrous membrane was enhanced rather than that from the reverse direction of the same membrane. The optimal water vapor transmission capacity existed when the electrospinning time of CA fibrous membrane reached 15 min. Such enhanced water vapor transmission originated because of the asymmetric wettability of the Janus membrane and the strong force to draw tiny water droplet from the hydrophobic side to the hydrophilic side. The novel understanding is useful for facile designing and fabrication of efficient moisture permeable fabrics and clothing.

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Personal wet–thermal management, which focuses on adjusting the moisture and temperature in a “human skin–wearable fabric–external environment” microclimate system, is the basis for ensuring the comfort of human beings and has recently attracted tremendous attention owing to its substantial significant role not only in ameliorating the health conditions but also in smart textiles for personal protection, electronic wearable devices, health monitoring, and so on. However, wearable fabrics focusing on personal comfort, especially wet–thermal dual-mode management, viz., including both efficient sweat removal and heat retention performances that provide protection for outdoor sports or work in a cold environment, still present huge challenges in their design, fabrication, and practical application. A Janus membrane with asymmetric wettability (superhydrophobic/hydrophobic–superhydrophilic/hydrophilic) along the thickness direction shows a unique directional water transport capacity, acts as a “water transport diode”, and is expected to be helpful to expel sweat/moisture efficiently from the human body to the external environment. Herein, we fabricated a hydrophobic/hydrophilic Janus membrane decorated by MXene (Ti3C2T x ) multilayered nanoflakes with outstanding photothermal conversion capacity via facile electrospinning combined with in situ polymerization. By virtue of asymmetric wettability and directional wicking, water and moisture can be driven from the hydrophobic layer to the hydrophilic layer, providing the Janus membrane with excellent directional water and moisture transport capacity. Furthermore, the successful decoration of MXene multilayered nanoflakes imparts electrical-power-independent heat retention capacity to the Janus membrane, resulting from the excellent photothermal conversion capacity of MXene. This work provides an insight into the facile design of Janus membranes for wet–thermal management and establishes a promising strategy not only to maintain personal comfort to ameliorate the health conditions as well as to improve the work efficiency of outdoor laborers in a cold environment but also to guarantee the special functions of smart wearable and multifunctional fabrics.