make 2.0 wt % PMMA solution in acetone. Tried also toluene as a solvent but difficulty arises in PMMA removal later on. stir it with magnetic stir for 10 hours until clear transparent solution is left.
Use spincoater equipment - set adjustments according to desired thickness. In my case the most suitable was 3000 rpm for 45 sec,
After testing the equipment , use dropper to cover the whole graphene on Cu foil with PMMA solution, no portion should be left dry .
After the spin coater process is complete bake it for 1-2 min at 80oC to bond the PMMA layer properly with the sample.