Mechanics of Fibrous Biological Materials With Hierarchical Chirality

Abstract

Chirality simultaneously exists at different length scales in many biological materials, e.g., climbing tendrils and bacterial flagella. It can transfer from lower structural levels to higher structural levels, which is tightly associated with the growth and assembly of biological materials. In this paper, a continuum mechanics model is presented for understanding the bottom–up transfer of chirality in fibrous biological materials. Basic physical mechanisms underlying the chirality transfer in biological world are revealed. It is demonstrated that the chirality of constituent elements at the microscale can induce the twisting of higher-level structures, which may further transfer into the macroscopic morphology in different manners, rendering the formation of hierarchically chiral structures in tissues or organs. The bottom–up transfer mechanism of chirality may provide a limit to the macroscopic size of biological materials through the accumulative contribution of twisting.