Researchers at UCLA and the University of Bologna have come up with a nano-size vehicle that can inch its way forward on sunlight and one day could, conceivably, be used to shuttle medicines or other small particles around.
The motor in chemical terms is a rotaxane, a mechanically interlocked molecule consisting of a ring trapped on a rod by bulky stoppers at both ends in the same way that rings are kept on an abacus. The ring in a sense serves as the foot. It is attracted to one end of the rod, called Station A, and moves toward it until it hits the stopper. The ring then moves to the second port of call, Station B, and moves toward it until halted by the opposite stopper. By alternating between Stations A and B, the ring pulls the whole contraption forward.
The attraction and repulsion is accomplished through electron harvesting. One of the ends of the barbell harvests an electron from sunlight and transfers it to Station A. When Station A contains an electron, the ring moves toward Station B. When Station A returns the electron to the barbell, the ring moves toward it.
A full cycle is carried out in less than a thousandth of a second, which means that the motor can operate at a frequency of 1,000 Hertz, according to the researchers. This is equivalent, using the car engine analogy, to 60,000 revolutions per minute.
“The kind of nanotechnology that will emerge from these nano motors still requires a lot of fundamental work. The nano motors are extremely sophisticated in their design,” Fraser Stoddart, UCLA’s Fred Kavli chair of NanoSystems Sciences and director of the institute, said in a statement.
Last year, researchers at Rice University showed off nanocars. These were propelled by external electric fields and did not generate their own energy, which the UCLA motor does. However, the Rice vehicles had moving molecular wheels.