The 200-year-old Stirling engine has inspired a power generator made of a single particle just 3 micrometres wide.
Overshadowed by its steam and internal combustion brethren, the Stirling engine is a quiet, efficient alternative that compresses a fixed amount of gas inside a cylinder.
As it is compressed, the gas heats up and expands, pushing a piston, before cooling due to the loss of energy, only to be compressed again.
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In their tiny mimic, and Valentin Blickle at the University of Stuttgart, Germany, replaced the cylinder with a laser that confines the motion of a 3-micrometre-wide lump of melamine in water.
Pent-up particle
A zap of heat from another laser builds up tension in this optical 鈥渢rap鈥�: like a compressed gas, the particle is aching to break free. Widening the trap by modifying the first laser lets it do so, expending the pent-up energy.
鈥淭he use of a laser source to provide the required rapid localised heating on the microscopic scale appears to be novel,鈥� says , leader of the Stirling Cycle Research Group at the University of Canterbury in Christchurch, New Zealand. He calls the technique sophisticated but says that he 鈥渟truggles鈥� to envision any practical applications.
But Bechinger says that the microscopic engine is allowing his team to investigate the balance between maximum power and maximum efficiency on the nanoscale 鈥� which could in turn inform the design of future micromechanical machines.
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