Scientists recently discovered that very different from the widely studied E. coli, sperms and paramecia that use flagella and cilia to swim, Eutreptiella gymnastica, Dictyostelium and neutrophils can swim by changing their shapes, which contradicts the dogma that amoeba cells can only crawl on substrates. Furthermore, immune cells and cancer cells undergo frequent shape changes (amoeboid motion) when migrating within a 3D extracellular matrix, allowing them to move forward in the porous media without the aid of adhesion sites. On the other hand, cells can also form a stable bleb and use the contractile cortical flow to propel themselves. In this talk, we used Helfrich's elastic curvature model to construct a deformable cell model, discovered the effect of spatial confinement on swimming behaviors and revealed the scaling laws and spontaneous symmetry breaking under different confinement strengths. We further studied the synchronization and collective modes of multi-cells under different confinement strengths. In addition, we studied a stable-bleb-driven cell migration utilizing cortical flow, characterize the relation between shape and swimming speed, and used simulation to reproduce cortical flow consistent with the experiment. At last, we studied the predatory behavior of Dictyostelium cells using chemotaxis under the external bacterial signal gradient field, and how bacteria use rheotaxis to escape the chase of Dictyostelium. We expect that physical models can provide some theoretical guidance for migration of immune cells and cancer cells in fluids. 

Dr. Hao Wu obtained Ph.D. in physics at University of Tokyo. He did his postdocs at Laboratoire Interdisciplinaire de Physique in France, University of Minnesota Twin Cities and UMass Amherst in USA, respectively. He has received the research grants from National Science Foundation of China, Zhejiang Province, and Songshan Lake Materials Laboratory, including the Zhejiang province overseas recruitment program of global thousand talents youth program and the Peng Huanwu junior visiting professor of the innovation research center for theoretical physics at ITP-CAS. He is now a professor at Wenzhou Institute University of Chinese Academy of Sciences. He has worked on soft matter, active matter and biohydrodynamics, especially on individual and collective behaviors of active colloids and deformable cells.

Please contact phweb@ust.hk should you have questions about the talk.