A micro steam engine is developed based on Newcomen steam engine. In the micro engine, a flexible ripple tube takes the place of piston and cylinder, to overcome the serious problems of friction and leakage in micro scale. We use two-phase octane as working fluid of the micro engine, because two-phase octane has higher power density than gaseous one. The micro engine is tested under different operational conditions to investigate its performance. It produces a maximum net mechanical work of 0.405 J per cycle with an efficiency of 2.58%. This experiment proves the feasibility of the micro steam engine. (C) 2010 Elsevier Ltd. All rights reserved.