spin-coaters, coating things evenly in general

[Nathan McCorkle]

On Mon, Feb 4, 2013 at 10:19 PM, Marc Dusseiller <dus...@gmail.com> wrote:
> and spin coaters are useful... made one from pc-fan and old harddisc drives
> http://hackteria.org/wiki/index.php/Spin_Coater

So is there some kind of cohesive network action between the polymer
solution keeping the thickness uniform, or does in fact the thickness
of a spin-coated layer vary from the center to the outside edge
(molecules in center feel lower Gs than molecules at the
circumference)?

Would it make sense to spin-coat something on a plane parallel to the
axis of rotation? Like those carnival rides where you stand up against
the inner side of a circular wall, and the ride spins around pressing
you to the wall. Replace the wall with a flat piece of polished
aluminum, and you with some gel that you way to spread evenly.


--
-Nathan

[Marc Dusseiller]

hei nathan,

spin coating has already been studied, optimized and done... been working too long in cleanrooms.

and miraculously it does generate very uniform films, down to nanometers... the surface needs to be clean and flat though.

it's some combination of viscosity, and rotation speed. also there is some evaporation happening at the same time. a lot of the excess liquid polymer is shot off the substrate, so the amount dispensed is not uniformely applied, but onyl a small film remains of it. and the wind blowing over the substrate plays also a role, meaning lid closed or opened. but there is whole books written about spin coating, being the most important step in the making of computerchips.

i built one in an old record player. was to slow though. but then the case and the lid was quite usefull. i just add a computer fan in the middle and double sided tape. (we did that in the clean room as well...)

all the best,

m