Macrophage is one of the immune cells in organisms which differentiate from monocytes and reside in various organs and is indispensable to our innate and adaptive immunity. However, the mechanism of phagocytosis is only partially understood, with key insights provided more than three decades ago. For example, the zipper model explained the driving mechanism of the engulfment procedure and its specific identification of antigens during phagocytosis in macrophages. To confirm the ability and limitation of this Zipper model in the critical conditions, we tracked the progression of the macrophage membrane engulfing the IgG-coated polystyrene beads and IgG-coated microneedles after reaching the maximum engulfment capacity. The results showed that the irregular membrane backtracking as the reverse phenomenon of engulfment was observed after macrophages reached the maximum engulfment capacity regardless of the difference of the shapes of antigens. We also evaluated the correlation of engulfment in simultaneous or series stimulations of two IgG-coated microneedles and found that they both reversed independently. However, the critical elongation size of membrane extension in each microneedle was smaller than the single microneedle engulfment. These results indicate that the mechanism of engulfment should imply (1) the function of reverse engulfment after they reach the maximum capacity before the completion of engulfment was included for their survival, and its recovery, (2) asynchronous backtracking in two-microneedle stimulation indicates the phagocytosis is the local phenomenon of macrophage membrane, and (3) the decrease of the maximum capacity in each of two-microneedle stimulation suggests the maximum capacity is not determined only by mere local cell membrane capacity but also by whole-cell volume increase information.