the outlet channel 3 of the pump via the intermediary of a communicating orifice 20 the construction of the micropump that has just been described is known per se and no detailed operating description will therefore be given particularly since this may easily be reconstructed from the following description of this construction the process of manufacturing the pump body 4 will now be described emphasising the essential features of the instant invention which as already indicated at the beginning of this text are directed at improving the hydrophilic properties and resistance to the aggressivity of the fluids to be pumped of the surfaces of the pump body 4 in contact with this fluid during the operation of the pump fig3 a to 3j represent diagramatically a partial sectional view of a pump body 4 taken along the line iii iii of fig1 a and 1b during various stages of the process of the invention it should be noted that in the following description of the process the values of all parameters such as layer thicknesses time spent in furnaces etc are only given by way of example and should not be considered as limiting to the instant invention a silicon piece 21 in which several pump bodies may be formed simultaneously using conventional technology is first subjected to wet oxidation stage of fig3 a which forms an oxide layer 22.