Locally Insulated Electrodes

Examples of electrodes with access holes in       oxide layer

Electrodes embedded into a microfluidics chip can be used to make electrical contact with gas and fluids. Micronit has perfected a method to locally insulate these contact electrodes using a thin oxide layer on top of the electrodes.

These electrodes can be useful for several applications:

1. Pumping and valving
   As a result of a local modification of the zeta potential, the direction of the local electro osmotic flow can be reversed, which in turn can be used for valving or pumping purposes.
   
   
2. Preventing electrolysis
   Application of electric fields inside microchannels, without generating electrolysis by preventing direct contact of the high voltage with the liquid. In this case no direct contact with the fluid is created. The small thickness of the insulation layer ensures a low voltage drop across the insulation layer, resulting in efficient generation of the electric field. This could for instance be used for dielectrophoresis (DEP) of cells. 
   
   
3. Protected electrodes
   Contactless conductivity detection using extremely thin insulating layers or contact conductivity detection with locally exposed electrodes.

Process Flow
First, electrodes are deposited onto the glass. Subsequently the oxide layer is deposited. By locally removing the oxide layer the access points to the electrodes are created. In the final step the electrode wafer is bonded to a wafer with for example microfluidic channels.

     Glass

     Electrode

     Oxide Layer