Hi:
I am surprised by the 10-20 um Pt particle size! There
is nothing like this in Sylgard 184? Do you mean 10-20
nm? We routinely make 10-20 um thick PDMS films
without any problem, at 6000 rpm.
For thicker films, 0.2-1 mm, we use intercalate of the
required thickness (usually LDPE films) and just pour
a small amount of the prepolymer, wipe the excess and
let it cure at RT. Most of the time, very flat
surfaces are obtained.
Karim Faid

--- "Z.,W.Y.(Lydia)"  wrote:
> Dear all,
>..  Sylgard 184 is 2 parts
> products. When you mix them together,
> the curing agent (Pt particles) will distributed
> randomly. When you film
> thick is smaller than the particle diameters
> (~10um-20um), you can observed
> this very clearly.