Microscopic steam engine built

BBC : Clemens Bechinger of the Max Planck Institute for Intelligent Systems at the University of Stuttgart and his colleagues have built a tiny steam engine based on the Stirling engine invented in 1816. Bechinger and his team wanted to know if the engine’s basic operating principle would work at the microscale. To adapt the engine to that size, they replaced the original design’s cylinder of gas with a micron-sized particle of melamine submerged in a tiny chamber of water. A focused IR laser beam took the place of pistons and acted as optical tweezers to hold the melamine in place. A second laser was used to heat the water, which cooled back to room temperature as soon as the laser was turned off. The micro-engine was as efficient, but not as stable, in its energy production as a full-sized Stirling engine. Water molecules in the solution surrounding the melamine constantly collided with the microparticle, causing energy to be passed back and forth. In a larger engine the amount of energy generated makes such collisions irrelevant, but in the microscopic engine the energy levels are too similar. While the micro-engine isn’t a practical power source, the team’s research could be used to create more stable power sources for micromachines.