▎ 摘　　要

NOVELTY - The method involves preparing porous film floating on a water surface, depositing a graphene on a metal substrate face up in water, obtaining a porous film-magnetic-metal substrate composite structure, wet etching the metal substrate in the porous film-magnetic-metal substrate composite structure to obtain a self-supporting porous film-graphene composite film on a liquid surface, immersing the substrate fixed with a batch metal microgrids in liquid where the porous film-graphene composite film is located, picking up the porous film-magnetic-metal substrate composite film to obtain metal microgrid-graphene-porous film composite structure or placing the substrate with the batch of metal microgrids fixed, and slowly pumping out the water to obtain metal microgrid-graphene-porous film composite structure, where the porous film is a gold film or a carbon film and the metal microgrid is made of gold, copper, nickel, molybdenum or non-metallic material silicon nitride. USE - The method is useful for preparing metal microgrid-graphene-porous film composite structure in field liquid phase electron microscopy imaging or cryo-electron microscopy imaging. ADVANTAGE - The method: utilizes the graphene-porous film-graphene sandwich liquid pool structure for multi-dimensional electron microscope imaging; precisely controls the thickness and volume of the liquid pool, so that the arrayed structure is conducive to high-efficiency data collecting; and freezes the liquid pool structure to obtain an ice layer with uniform thickness, which has important application prospects in the field of high-resolution microscope imaging field. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a preparation method of graphene-porous film-graphene sandwich liquid tank structure. DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the preparation method of graphene-porous film-graphene sandwich liquid tank structure (Drawing includes non-English language text).