If you’ll be asked about the size of the smallest electric motor, what would your answer be? An inch? A millimeter? The correct answer is, astoundingly, a nanometer across. That is 1/60,000 the size of a single strand of human hair.
Researchers from Tufts University are credited for building such super tiny electric motor. The research team is led by Charles Sykes, the associate professor of chemistry in the said university. The motor, the subject of the research paper published by Nature Nanotechnology, has been awarded a Guinness World Record for the smallest electric motor. It broke the previous record of 200 nanometers. The research was funded by the National Science Foundation, Research Corporation for Scientific Advancement and the Beckman Foundation.
The motor is, in fact, a single-molecule – which is not new – but this invention by Sykes and company is the first one to be powered by electricity. The previous single-molecule motors were either light or chemically driven which Sykes says are disadvantageous compared to their invention.
Mechanism of work
The single-molecule motor is made possible through a scanning tunneling microscope (a type of electron microscope that shows three-dimensional images of a sample) which can land on top of a molecule and spin it. At the end of the microscope is a metal tip that can be used to apply electricity to a molecule – butyl methyl sulfide, in this case. This molecule, placed on top of a copper surface, has a sulfur atom at the center and carbon atoms forming the motor’s armature. The application of electricity spins the molecule over the copper surface at a rate proportional to temperature.
The operating temperature is critical in the operation of the motor and, in fact, can be a limiting factor. For Sykes experiment, the temperature must be reduced to -450 °F for it to spin 50 revolutions per second. Increase that temperature to -279 °F and the single molecule motor spins more than a million times per second!
Because of the unnatural temperature range needed to operate the single molecule motor, practical applications are still in the far future. Sykes though sees their invention usable in the medical field and in instrumentation. One particular application he cites is that of very tiny tubes like in 3d printed capillaries. At such minuscule sizes, the friction on the wall of the tubes increases significantly. The friction can be decreased if their single-molecule motor is attached to the walls.
Another area where the single molecule motor could flourish is in nanoelectromechanical systems or NEMS. NEMS technology is seen as the next level to current microelectromechanical devices (MEMS) devices. With a nanometer-sized motor, Nano-sized mechanical devices and sensors would not be far away.
Professor Sykes and his team are looking to solve the temperature constraints as funding for the research continues. It is interesting to note that Sykes research team includes high school students among doctoral students. Nikolai Klebanov and Harout Y. Khodaverdian were both high school students when they worked with the research team. Along with Sykes, Klebanov, and Khodaverdian are Heather L. Tierney, Ph.D., Colin J. Murphy, Ph.D., April D. Jewell, Ph.D., Ashleigh E. Baber, Ph.D., Erin V. Iski, Ph.D. and Allister F. McGuire.