Potential sources of worries:
- "On a silicone film". If the polyimide is removed (is it?), the very extensible silicone film may break the metal.
- Does platinum need annealing after sputtering? Being a rather refractory metal, it may demand more than what silicone and polyimide withstand.
On usual silicone I'd worry because of poor adhesion. If silicone is made "adhesive" (how poorly?) this would rather reassure me.