Phase field collagen fibrils: modelling both axial and radial structure of collagen fibrils

Collagen fibrils are rope-like biomaterials that provide structural integrity to tendons, skin, and other tissues in the human body. These fibrils self-assemble from aggregates of collagen molecules. Decades of experimental research have uncovered many properties of collagen fibrils, from the ubiquitous "d-band" (periodic modulations of density along the cylindrical axis of the fibril) to the twisted orientation of molecules visible at the fibril surface. While models exist of either the axial d-band or of radial double-twist structure, reconciling the radial and axial structure has only been done qualitatively with a projective coupling hypothesis. In this talk, I present a coarse-grained model of collagen fibrils that combines liquid crystal theory and phase-field-crystal techniques, and uses simple equilibrium arguments to predict both the collagen fibril d-band spacing and the radial double-twist describing the average molecular orientation.