Wettability and filling of small channels, nano to micro range and

Hey everyone,

I'm trying to get an estimate using simulations for a microfluidics (or nanofluidics) problem.
The problem is as following, there's a very narrow channel or slot if we run a fluid like water over it will it fill the channel or slot. The slot has a depth of 220 nm and a width ranging somewhere from 200nm to 20nm (100nm is a good first estimate). The question is how much of the slot will be filled with water if we just run water over it.

Another approach bringing the second question is how much initial pressure is generated if we force a flow through this channel/slot.

I thought about first approaching this problem by doing a qualitive 2-D analysis with with a geometry as shown in the attached image. The first region (from the left) is filled with water (material water) the rest is air. All the walls are set with a wetted condition and angle except from the inlet and outlet ofcourse ( 1 um/s flow from left to right, outlet 0 Pa).

What do you guys think is the best way to solve these kind of problems.
Is this even something that would give proper results in comsol?
Is it maybe better to do this in Fluent (ansys)?

Any suggestions, tips?