Molecular propellers designed by Prof. Petr Kral's group are molecules that have blades serving as efficientpumps of liquids.
The molecular propellers designed in the group of Prof. Petr Kral from the University of Illinois at Chicago have their blades formed by planar aromatic molecules and the shaft is a carbon nanotube. Molecular dynamics simulations show that these propellers can serve as efficient pumps in the bulk and at the surfaces of liquids. 
