A first closed enclosure defines a cavity having an inner dimension smaller than 5 mm. At least one second resiliently deformable closed enclosure is connected in fluid communication with the first enclosure. A fluid at more than 90% in the liquid state fills the first and second enclosures. A first portion of the first enclosure is in contact with a hot source of a temperature higher than the evaporation temperature of the fluid. A second portion of the first enclosure located between the first portion and the resiliently deformable closed enclosure is in contact with a cold source at a temperature lower than the condensation temperature of the fluid. An electromechanical transducer is coupled to a deformable membrane of the resiliently deformable closed enclosure.