Fig. 1. Graphene roughness dominates the uniformity of ice thickness.

a, Schematic illustration of wrinkled rough graphene resulting in wavy ice with inconsistent ice thickness, which can result in a focal height difference (ΔH) of 10–20 nm. The protein particles are shaded by the wrinkled graphene during cryo-ET imaging. Note that the wrinkles in graphene include the ripples and folds, as shown in the side view of wrinkled suspended graphene. b, Schematic illustration of pre-tensioned UFG resulting in a uniform ice layer, with proteins adsorbed on the UFG at the same height.