Dear All,

This is with reference to my earlier question on metallization on
PDMS. Few problems which I am still facing with regards to
metallization on PDMS are as follows-

1) I have only a Chrome layer (~20nm) onto PDMS. For patterning this
layer, I spin coat positive resist (Shipley S1813) and pre-bake
(keeping the pre-bake temperature to as low as 45C). When I try to
etch chrome, the layer of chrome remains intact, i.e. to say there is
no etching even after 30mins in etchant (ceric ammonium nitrate
+acetic acid mix). While the sample of chrome on PDMS which is not
patterned gets etched easily. Can it be some kind of diffusion of
chrome in PDMS while pre-bake of resist which is not allowing it to
get etched?

2) Gold film on PDMS once etched in KI+I2+water mix imparts a reddish
colour to PDMS. The colour is of etchant and it is not removed even
after sonication in acetone and water. Is it due to the etchant
getting adsorbed by PDMS? Will it change the properties of PDMS?

Apart from the above queries I would also like to know has anyone ever
tried patterning PPR onto PDMS say for a lift-off process? I have
tried spinning PPR directly on PDMS and also spinning HMDS first and
then PPR. In both the cases PPR is not sticking to PDMS. Can someone
please suggest some way by which I can spinh coat uniform layer of PPR
onto PDMS.

Thanks and warm regards,
Nidhi