We report on the design, modeling, fabrication and testing of a powerful electrothermal actuator allowing for various modes of movement and exhibiting forces large enough to be usable in a micro-tribotester. The performance of the actuator has been simulated combining numerical and analytical calculations, and then the results were compared with experiments performed in ambient conditions and in vacuum. Theoretical results and measurements are consistent if the temperature dependence of the properties of the polycrystalline Si is taken into account. The temperature dependence of the electrical resistivity and the linear thermal expansion coefficient of the Boron doped polycrystalline Si have been derived from experimental results and self-consistent numerical calculations. We delimited the reversible and irreversible actuation regions of the electrothermal actuator, thus the so-called ldquoplastic deformationrdquo for actuation at high electrical power can be avoided. The authors would like to thank the financial support of the Dutch Technology Foundation (STW) and the technical support of the TST (Micmec) technicians.