Study On Model Of Chirality Transfer And The Stretch-twist Coupling Deformation In Biological Materials

Chiral materials have a good application prospect in many fields of recognition and separation of chirality,stealth materials and device,biosensor due to unusual elastic,optical,electrical and magnetic properties.In this paper,we preliminarily studied the hierarchically chirality transfer and the mechanical principle of hierarchically chirality transfer and the chiral properties of the materials in the growth or assembly of chiral materials.Chirality simultaneously exists at different length scales in many biological materials,forming hierarchically chiral structural materials.e.g.,climbing tendrils and bacteria flagella.It can transfer from lower structural levels to higher structural levels,which is tightly associated with the growth or assembly of biological materials.In this paper,a general theoretical model is presented.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 biological materials.The bottom-up transfer mechanism of chirality may provide a limit to the macroscopic size of biological materials through the accumulative contribution of twisting.Chiral microstructures of the helical or twisted inclusion usually endow biological materials manifesting obvious stretch-twist,bend-shear coupling deformation.The extent of coupling deformation reflects the size of material chirality.In this paper,we study the nonlinear variation of material chirality on one-dimensional chiral materials under large elongation,which is used to explain the reversal phenomenon of DNA.It is further discovered that the interaction between chiral microstructures in different length scales for the materials with hierarchically chiral microstructures also induce the nonlinear variation of material chirality.