UV/mask irradiation and heat induced switching on–off water transportation on superhydrophobic carbon nanotube surfaces

We used a simple spray-coating process to prepare superhydrophobic carbon nanotube (CNT) surfaces with a water contact angle (CA) of 160° and a sliding angle (SA) of 3° on desired substrates without any chemical modification. After being irradiated by UV light through a photomask, the as-prepared low adhesive superhydrophobic CNT surface changes to high water adhesion. However, further heating the irradiated CNT surface, the irradiated CNT surface becomes its original low water adhesion again. Reversibly switchable transition between the low water adhesion and high water adhesion can be realized simply by UV/mask illumination and heat treatment alternately. Simultaneously, the adhesive force of the superhydrophobic CNT surfaces changes from low (~ 8.9 μN) to very high (~ 133.6 μN). Based on the reversible water adhesion transition on the superhydrophobic CNT surfaces through UV illumination and heat treatment alternately, switching on–off water transportation was achieved. This switchable water adhesion on the superhydrophobic CNT surfaces could have potential applications in areas requiring multifunctional CNT-based surfaces.