Abstract: A method of ex situ fabrication of at least one biochip, the method being of the type consisting in projecting onto a substrate a microvolume of reagent comprising at least one probe diluted in a suitable solvent so as to form, after the solvent has been eliminated, a spot comprising said probe, the method consisting in using a microprojection device comprising at least one tank in which the reagent is stored, and at least one source of gas under pressure put into communication with the tank, and in projecting the microvolume of reagent through an ejection nozzle under drive from the pressure exerted by the gas on the reagent.