The present invention relates to a microfluidic analysis device (1) including: a substrate (20) wherein a separation channel (10) is arranged, in which an electrolyte flows, a portion of the separation channel (10) being covered with a polarizable surface (11); two longitudinal field electrodes (8a, 8b) arranged on either side of the separation channel (10); at least one control electrode (6a, 6b) positioned in the separation channel (10), the control electrode (6a, 6b) being suitable for polarizing the polarizable surface (11) so as to control the speed of the electro-osmotic flow in the separation channel (10); the microfluidic analysis device (1) being characterised in that the polarizable surface (11) includes an insulating sub-layer (12) made of amorphous silicon carbide (SiC) and an upper polarizable layer (13) in direct contact with the electrolyte, the control electrodes (6a, 6b) being positioned between the insulating sub-layer (12) and the upper polarizable layer (13).