A novel Janus fabric with stable amphibious directional oil transport function

Directional oil transport (DOT) in porous matrices shows broad application potential in microfluidics, oil–water separation, and “smart” textiles. The existing DOT materials work only in either air (dry state) or underwater environments. It remains a significant challenge to develop materials with DOT capability in both air and water medium. This study prepares a novel Janus fabric with amphibious DOT property in both air (dry) and underwater environments. The DOT fabric is prepared by a dip-coating method to apply glycerol propoxylate triglycidyl ether and octadecylamine onto a fabric substrate and subsequently electrosprayed with a fluorine-containing copolymer containing both oleophobic and hydrophilic groups onto one side of the fabric. The developed Janus fabrics show stable superamphiphilicity (both hydrophilicity and oleophilicity) on the non-electrosprayed side and hydrophilicity-oleophobicity on the electrosprayed side. The opposite oleophilicity and oleophobicity feature on the two sides endows the Janus fabric with amphibious DOT property to oils with surface tension in the range of 24–32 mN/m. Without any pre-treatment, the fabric can spontaneously guide oil to transport directionally from the oleophobic side to the oleophilic side but prevent the oil from transporting in the opposite direction. This DOT property is durable and can withstand numerous harsh treatments, e.g. repeated washing and abrasion, long time storage, ultrasonication, strong acid and base attacks. To our knowledge, this is the first report of amphibious directional oil transport Janus fabric. The unique amphibious air–water DOT property enables the Janus fabric to be used for water/oil separation and underwater oil collection. Such a novel fabric may have many potential applications, such as microfluidic valves and oil–water separators. The results from this work can be extended to develop an oleophilic/oleophobic diode.