Growth strain-induced wrinkled membrane morphology of white blood cells

The membranes of white blood cells possess a highly corrugated or wrinkled surface topology. This topology provides excess surface area which serves as a reservoir for membrane expansion during osmotic swelling and for membrane mediated events such as adhesion and sensing. We explore and model the dynamic development of the wrinkled morphology to arise from buckling instabilities triggered by the deformation mismatch between the membrane and the cytoskeleton during membrane growth. In particular, we examine the formation of the wavelengths and amplitudes of the wrinkled topology during the large deformations of the membrane growth, which lead to the experimentally observed spicule-like character of the topology. The anisotropic nature of the membrane structure and mechanical behavior, in particular the high stiffness resisting surface area change which provides a high biaxial bending stiffness of the membrane, are found to play an important role in topology development.