Dear All,

At low reynolds number system, surface tension is an important factor

affecting the fluid dynamics. So I have a question about bubbles, the

shrinking dimensions(low R), etc.

For example, if there is a box x=1cm, y=1mm, z=1cm, the volume will be

100 ul. If I fill 60ul of solution from a small hole at XY plane, the

box will be more than half full. The box is rotated around y axis, the

minuscus can cover the full surface of XZ plane 1cm*1cm. If I only

give it 40ul, the box will be less than half full so the surface of XZ

plane will not be fully covered when the box is roated along Y axis.

It will leave a round pattern uncovered in the middle. Agree?

But if I decrease Y thickness from 1mm to 100um (0.1mm), I believe the

surface tension will hold the solution so tight that the minuscus (at

the height of Z=6mm for 60ul of solution) will be very difficult to

move when the box is rotated. The surface tension pressure is given by

Laplace law P=2(gama)cos(theta)/r. gama is surface tension coeffecient

of the solution, theta is the contact angle and r is the radius of the

curvature of the interface.

I'd like to calculate the rotational force/speed needed (if

reasonable) to move the solution/air interface (ie. overcome surface

tension) as it did in the above example. But I don't have a clue. As

things change from macroscopic to miscroscopic, it gets complicated

and many surface effects have to be taken into consideration.

Thanks a lot if you can shine some light on it!

Frank