he aim of this article is to show the different boiling heat transfer regimes identified by Nukiyama (1934) in a micro-exchanger during a falling film evaporation. This study allows establishing operating conditions to develop the micro-evaporation or the micro-distillation where heat transfer has to be intensified. Indeed, the behaviour of binary mixtures on heat transfer is sometimes different than with a pure compound. The present study investigates the evaporation of ethanol in a sandwich plate micro-heat exchanger. Ethanol is a chemical test. It streams by gravity in falling film on two symmetrical heated micro-structured plates where micro-straight vertical channels have been machined (Kane et al., 2011). Electrical heat fluxes ranged from 2 to 5 kW/m(2). Various differences of temperatures between wall and saturation temperature were tested. Feed flow rate ranged between 1 and 5 g/min (smooth laminar flow: 2