Microfluidic analysis device and method

1. A microfluidic analysis device ( 1 ) including:

a substrate ( 20 ) wherein a separation channel is arranged, in which an electrolyte flows, a portion of the separation channel ( 10 ) being covered with a polarisable surface ( 11 );

two longitudinal field electrodes ( 8 a , 8 b ) arranged on either side of the separation channel ( 10 );

at least one control electrode ( 6 a , 6 b ) positioned in the separation channel ( 10 ), the control electrodes ( 6 a , 6 b ) being adapted to polarise the polarisable surface ( 11 ) so as to monitor the rate of the electro-osmotic flow in the separation channel ( 10 );

the microfluidic analysis device ( 1 ) being characterised in that the polarisable surface ( 11 ) includes an insulating sub-layer ( 12 ) made of amorphous silicon carbide (a-SiC) and an upper polarisable layer ( 13 ) in direct contact with the electrolyte, the control electrodes ( 6 a , 6 b ) being positioned between the insulating sub-layer ( 12 ) of amorphous silicon carbide (SiC) and the upper polarisable layer ( 13 ).

2. The microfluidic analysis device ( 1 ) according to claim 1 , wherein the upper polarisable layer ( 13 ) is of nitrogen carbon (CNx).

3. The microfluidic analysis device ( 1 ) according to claim 1 , further comprising:

a reference electrode ( 7 a , 7 b ) adapted to measure the potential of the electrolyte in the separation channel ( 10 );

a monitor circuit ( 50 a , 50 b ) adapted to adjust the potential of the control electrode ( 6 a , 6 b ) as a function of the electrolyte potential measured by the reference electrode ( 7 a , 7 b ), such that the polarisable surface ( 11 ) remains in its polarisability window.

4. The microfluidic analysis device ( 1 ) according to claim 3 , characterised in that the monitor circuit ( 50 a , 50 b ) is adapted to impose a fixed potential difference between the control electrode ( 6 a , 6 b ) and the reference electrode ( 7 a , 7 b ).

5. The microfluidic analysis device ( 1 ) according to claim 1 , characterised in that it includes at least:

one upstream control electrode ( 6 a ) positioned upstream of the channel;

one downstream control electrode ( 6 b ) positioned downstream of the channel;

one upstream reference electrode ( 7 a ) positioned upstream of the channel;

one downstream reference electrode ( 7 b ) positioned downstream of the channel;

the upstream control electrode ( 6 a ) is connected by an upstream monitor circuit ( 50 a ) to the upstream reference electrode ( 7 a ), the downstream control electrode ( 6 b ) being connected by a downstream monitor circuit ( 50 b ) to the downstream reference electrode ( 7 b ), the downstream monitor circuit ( 50 a ) being adapted to adjust the potential of the control electrodes ( 6 a , 6 b ) as a function of the electrolyte potential measured by the reference electrodes ( 7 a , 7 b ), such that the polarisable surface ( 11 ) remains in its polarisability window.

6. The microfluidic analysis device ( 1 ) according to claim 5 , the downstream monitor circuit ( 50 b ) being connected to a floating ground ( 59 ) referenced to the downstream reference electrode ( 7 b ).

7. The microfluidic analysis device ( 1 ) according to claim 6 , the downstream monitor circuit ( 50 b ) including a first operational amplifier ( 51 ), and a second operational amplifier ( 52 ), the downstream reference electrode ( 7 b ) is connected between the non-inverting input of the first operational amplifier ( 51 ) and the floating ground ( 59 ), and the downstream control electrode ( 6 b ) being connected between the non-inverting input of the second operational amplifier ( 52 ) and the floating ground ( 59 ).

8. A microfluidic analysis method implemented by a microfluidic analysis device ( 1 ) according to claim 1 including the steps of:

injecting an electrolyte containing analytes into the separation channel ( 10 );

generating a longitudinal field in the separation channel ( 10 );

polarising the polarisable surface ( 11 ) by applying a polarisation voltage across the control electrodes ( 6 a , 6 b ) and monitoring the electro-osmotic flow rate in the separation channel ( 10 ) by modulating the polarisation voltage across the control electrodes ( 6 a , 6 b ).

9. The microfluidic analysis method according to claim 8 implemented by a microfluidic analysis device ( 1 ), characterised in that during the step of monitoring the electro-osmotic flow rate in the separation channel ( 10 ), the polarisation voltage across the control electrodes ( 6 a , 6 b ) is adjusted as a function of the electrolyte potential measured by the reference electrode ( 7 a , 7 b ), such that the polarisable surface ( 11 ) remains in its polarisability window.

10. The microfluidic analysis method according to claim 9 implemented by a microfluidic analysis device ( 1 ), characterised in that during the step of monitoring the electro-osmotic flow rate in the separation channel ( 10 ), a fixed potential difference is imposed between the upstream control electrode ( 6 a ) and the upstream reference electrode ( 7 a ), and between the downstream control electrode ( 6 b ) and the downstream reference electrode ( 7 b ).