Formation of chiral morphologies of biological materials induced by chirality

Abstract

Chiral growth exists prevalently in natural materials. The mechanism underlying the formation of chiral morphologies in biological and man-made materials has been an important issue of both theoretical and technological interest. In this paper, an elastic rod model taking into account chiral microstructures is developed to investigate the formation of chiral morphologies of biological materials. The curvature and twist of chiral shapes are investigated with this model using the variational method of energy. The result shows the misfit of chirality of two-layer structured biological materials may induce various chiral morphologies, such as helices and twisting belts. Furthermore, it was found that cooperative or competitive interactions between anisotropic elasticity and chirality can also lead to the formation of chiral morphologies, and the fibre orientation angles and chiral parameters are the determining factors to the shape, size and handedness of chiral morphologies. This work is expected to shed new light on the physical mechanisms of the formation of various chiral morphologies in the biological world and provide useful guidance for the design of deformation driving and shape control of soft robots and machines.