Engineering Janus cellulose fabric with unidirectional water transport capability toward perspiration-induced cooling human body

Traditional cellulose fabric with high hydrophilic distinction realizes personal thermal management via perspiration-induced cooling for the human body. However, such behavior is restricted in high-humidity environments, where sweat/water transports from a high-humidity environment to the human body by hydrophilic cellulose fabric. Herein, we developed an environmentally friendly, low-cost, large-scale Janus cellulose fabric via one-side hydrophobic modification of hydrophilic cellulose. Our Janus cellulose fabric comprises hydrophobic cellulose side (water contact angle of 151°) and hydrophilic cellulose side (water contact angle of 19°). Such distinction endows Janus cellulose fabric with unidirectional water-transport capability, where water molecules are inclined to transport, diffuse and evaporate on the hydrophilic cellulose (diffusion area of 50 μl water is around 0.8 cm2) rather than the hydrophobic cellulose (less and even negligible diffusion area), correspondingly spontaneously leading to a 3–4 ℃ temperature drop of the human body when covering Janus cellulose fabric than pristine cellulose fabric. Janus cellulose fabric paves the way toward green, cost-effective, and cooling fabric in our sustainable society.