Microengines

Microengines are miniature devices that convert energy into mechanical work at scales ranging from tens of micrometers to a few millimeters. The category includes micro internal combustion engines, microturbines, and a variety of chemically or electrically powered actuators used in micro-robotics, microfluidics, and MEMS. In many cases, the term also covers catalytic microengines and other self-propelled systems that generate motion from chemical energy.

At small scales, surface forces, friction, and heat transfer dominate dynamics, so performance does not simply scale down from macroscopic engines. Power sources include chemical energy via oxidation or catalytic reactions, electrical energy via MEMS electrostatic or electromagnetic drives, and light or thermal energy. Efficient energy storage and thermal management are major design considerations.

Common implementations include micro internal combustion engines and microturbines demonstrated in laboratory settings; electrostatic comb-drive and magnetically driven microactuators; catalytic microengines that propel themselves by chemical reactions; and nano- or micro-scale Janus particle motors powered by fuel decomposition.

Fabrication typically relies on MEMS technologies, including lithography, thin-film deposition, etching, and assembly of microstructures from silicon, polymers, or metals. Integration with sensing, control electronics, and power delivery remains a key challenge.

Applications focus on micro-robotics, targeted drug delivery, lab-on-a-chip systems, and precise micropositioning. While there have been numerous exploratory demonstrations, microengines are largely at the research and development stage, with few commercial products, due to reliability, control, and energy-density limitations.