(color online) The endocytosis phase diagram in the space of radius and aspect ratio m of NP based on Eq. (10). The color bar indicates the values of endocytosis speed , the endocytosis in the dark blue region is impossible. The solid dark line and white line represent the theoretical optimal NP size and the threshold NP size for endocytosis, respectively. (a) Depletion effect, the dimension of ligand-receptor complex and membrane tension are not considered, its corresponding parameters, c, δ, and λ, are set to be zero. (b) The corresponding parameters utilized in Fig. 2(b) are listed as , δ = 6 nm, and .