Superhydrophobic alkanethiol-coated microsubmarines for effective removal of oil.

We demonstrate the use of artificial nanomachines for effective interaction, capture, transport, and removal of oil droplets. The simple nanomachine-enabled oil collection method is based on modifying microtube engines with a superhydrophobic layer able to adsorb oil by means of its strong adhesion to a long chain of self-assembled monolayers (SAMs) of alkanethiols created on the rough gold outer surface of the device. The resultant SAM-coated Au/Ni/PEDOT/Pt microsubmarine displays continuous interaction with large oil droplets and is capable of loading and transporting multiple small oil droplets. The influence of the alkanethiol chain length, polarity, and head functional group and hence of the surface hydrophobicity upon the oil-nanomotor interaction and the propulsion is examined. No such oil-motor interactions were observed in control experiments involving both unmodified microengines and microengines coated with SAM layers containing a polar terminal group. These results demonstrate that such SAM-Au/Ni/PEDOT/Pt micromachines can be useful for a facile, rapid, and efficient collection of oils in water samples, which can be potentially exploited for other water-oil separation systems. The integration of oil-sorption properties into self-propelled microengines holds great promise for the remediation of oil-contaminated water samples and for the isolation of other hydrophobic targets, such as drugs.