Grid membrane filters break through the performance boundaries of traditional filter media with their nano-scale grid-like pore structure. The formation of this precise structure is a deep integration of material science and engineering technology, relying on the ultimate control of membrane process parameters and precise regulation at the microscopic scale. From the molecular self-assembly of polymer membranes to the precise carving of microstructures, each process lays the foundation for achieving molecular-level filtration accuracy. As an important material for grid membrane filters, the construction of polymer membrane pore structure mainly relies on phase inversion method and thermally induced phase separation method. The phase inversion method achieves orderly growth of pores by cleverly regulating the transition process of polymer solution from homogeneous phase to multiphase. In the initial stage of membrane formation, the polymer is uniformly dissolved in a specific solvent to form a homogeneous solution, and then the solution is scraped into a membrane, breaking the system balance by immersion precipitation, evaporation induction and other methods. Taking the immersion precipitation method as an example, the coated membrane is immersed in a coagulation bath, and the solvent and coagulant quickly undergo double diffusion, resulting in liquid-liquid or liquid-solid phase separation of the polymer solution. In this process, parameters such as the evaporation rate of the solvent, the composition of the coagulation bath and the temperature become the key factors that determine the pore structure. When the solvent evaporates quickly and the coagulation bath and the solvent have strong mutual solubility, the polymer will quickly aggregate to form small and dense pores; conversely, a slower phase separation rate is conducive to the formation of a large-pore, high-porosity structure. By precisely adjusting these parameters, researchers can guide the self-assembly of polymer materials to form a regularly arranged pore array, providing a basic framework for the construction of subsequent grid structures. The thermally induced phase separation method (TIPS) takes a different approach and uses temperature changes to drive the phase separation process. This method uses a diluent that is completely miscible with the polymer at high temperatures and whose solubility drops sharply at low temperatures. After heating the polymer and the diluent to a homogeneous phase, the system undergoes liquid-liquid phase separation or liquid-solid separation by rapid cooling or controlling the cooling rate. As the temperature decreases, the diluent and the polymer gradually separate, and the diluent is dispersed in the polymer phase in the form of tiny droplets. The diluent is subsequently removed by extraction and other methods, leaving a pore structure in the membrane. Precise control of parameters such as cooling rate, diluent type and content determines the size, shape and connectivity of the pores. By optimizing the process conditions, the pores can be arranged in a highly ordered manner in the membrane to form a uniform pore network. After the initial pore structure is constructed, it is necessary to use micro-nano processing technologies such as photolithography and nanoimprinting to further carve the regular pores into a grid shape. Photolithography selectively exposes the membrane surface through a photomask to cause a photochemical reaction in the light-receiving area, and then accurately removes part of the material through steps such as development and etching to form a grid structure with a specific geometric shape. Nanoimprinting technology uses a mold with a nanoscale pattern to transfer the pattern to the membrane surface through mechanical pressure, so that the pore edges are accurately cut and reshaped, and finally neatly arranged grid-like pores are formed. These micro-nano processing technologies can control the pore size error at the nanometer level, ensuring that the shape, size and design parameters of the grid structure are highly consistent. The forming process of the nanoscale grid-like pore structure is essentially the precise manipulation of the behavior of matter at the microscopic scale. The parameter adjustment of each process link is like precision carving at the molecular level, from the phase separation self-assembly of polymers to the precise processing of micro-nano structures, and a microstructure with excellent filtration performance is constructed layer by layer. This precision-formed grid pore not only gives the filter the ability to accurately screen by size, but also achieves selective retention of substances of different forms through a unique geometric shape, making it show unparalleled advantages in the fields of protein separation and gas purification.