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 cm 2 ) 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.