Motility is an essential characteristic of many biological cells. It is crucial for the survival of unicellular organisms and required for many physiological functions in metazoans, such as immune response, embryonic development and cancer metastasis.
Some of the unicellular organisms propel themselves in fluid by cyclic deformation of their flagella. Recently, immune cells have also been shown to swim by periodic shape changes (“amoeboid swimming”). We have developed theoretical models to study the mechanical principles governing the amoeboid and flagellar swimming. Using these models we have studied the cell swimming under external forcing and flows to demonstrate gravitaxis and non-Newtonian rheological behaviors. We have also looked at the transition between the swimming and crawling modes of cell migration in the presence of adhesive substrate and obtained the conditions for the optimal cell movement.