The aim of nanotechnology is to scale down the machinery used in everyday life, in order to control and manipulate the nano-world just as well as we manipulate things our own size. And this latest development is a breakthrough of microscopic proportions: the single-atom engine.

German researchers were able to successfully construct a single-atom heat engine, and it could be the smallest heat engine ever built. The researchers also measured its energy output, 3.4 x 10^-22 watts, which by mass would make it equivalent to a typical car engine (1.5 kilowatts per kilogram) in terms of power. The results were published in the journal Science. 

Heat engines convert thermal energy into mechanical energy, a technological advancement that started the Industrial Revolution. During the past decade or so, there’s been a focus on miniaturization with the construction of smaller and smaller thermal machines.

Johannes Roßnagel and colleagues designed the single-atom engine to behave like a full-scale engine. They took a calcium ion and trapped it so that it could move exclusively along one axis. It was then subjected to two different temperatures, being cooled down by a laser beam while being heated by an oscillating electric field. The temperature difference generated motion along the free axis that was similar to the motion of a piston in an engine. 

Talking to IFLScience, Dr. Roßnagel discussed the technical sophistications necessary to achieve this result. "The obstacles have been both of a technical nature and of a conceptual nature," he said. "We need electronics with very low noise [interference], a camera with the shortest exposure times (700 nanoseconds), very good vacuum conditions, high control of the electric fields in the trap, and a high quality laser system."

"The crucial point is the high degree of control that is needed to run the engine, and, perhaps even more importantly, to read out the state (such as the temperature, energy, and position) of the atom," he added.

The engine has an efficiency of 0.28 percent, meaning only 0.28 percent of the total energy is converted into useful work. The result might seem terrible (the typical car engine has an efficiency of about 25 to 30 percent), but it is in agreement with theoretical expectations.

The single-atom engine has the potential to play a significant role in both applied and theoretical physics. Single-atom engines could power nanoscale technologies and even allow scientists to construct single-atom refrigerators. The researchers don't think there will be a direct "daily use" of this technology, though. 

"A whole lab of lasers, electronics, and vacuum chambers is needed to run this single atom engine," noted Dr. Roßnagel. "However, we do fundamental research and try to get a better understanding of the thermodynamics of single particles.

"This improved understanding can (and will, I'm convinced) lead to a next generation of experiments and future devices which have interesting applications."