Method and device for laminar flow on a sensing surface

A method of sensitizing a sensing surface arranged to be passed by a liquid flow within a flow cell, comprising:

• providing a laminar flow of a first sensitizing fluid capable of sensitizing the sensing surface, and a laminar flow of a non-sensitizing fluid adjacent to the flow of the first sensitizing fluid such that the two laminar fluids flow together over the sensing surface with an interface to each other,
• adjusting the relative flow rates of the first sensitizing fluid and non-sensitizing fluid to position the interface such that the first sensitizing fluid contacts a first discrete sensing area of the sensing surface for selective sensitization thereof,
• replacing the first sensitizing fluid by non-sensitizing fluid, and replacing the non-sensitizing fluid by the first sensitizing fluid or by a second sensitizing fluid that is capable of sensitizing the sensing surface, and
• adjusting the relative flow rates of the sensitizing fluid and the non-sensitizing fluid to displace the interface laterally such that the sensitizing fluid contacts a second discrete sensing area spaced apart from the first discrete sensing area of the sensing surface for selective sensitization thereof to produce two sensitized areas spaced apart by a non-sensitized area on the sensing surface comprising a third non-sensitized discrete sensing area serving as control.