Biological plywood film formation from para-nematic liquid crystalline organization

Abstract

In vitro non-equilibrium chiral phase ordering processes of biomacromolecular solutions offer a systematic and reproducible way of generating material architectures found in Nature, such as biological plywoods. Accelerated progress in biomimetic engineering of mesoscopic plywoods and other fibrous structures requires a fundamental understanding of processing and transport principles. In this work we focus on collagen I based materials and structures to find processing conditions that lead to defect-free collagen films displaying the helicoidal plywood architecture. Here we report experimentally-guided theory and simulations of the chiral phase ordering of collagen molecules through water solvent evaporation of pre-aligned dilute collagen solutions. We develop, implement and a posteriori validate an integrated liquid crystal chiral phase ordering-water transport model that captures the essential features of spatio-temporal chiral structure formation in shrinking film domains due to directed water loss. Three microstructural (texture) modes are identified depending on the particular value of the time-scale ratio defined by collagen rotational diffusion to water translational diffusion. The magnitude of the time scale ratio provides the conditions for the synchronization of the helical axis morphogenesis with the increase in the mesogen concentration due to water loss. Slower than critical water removal rates leads to internal multiaxial cellular patterns, reminiscent of the classical columnar-equiaxed metallurgical casting structures. Excessive water removal rates lead to destabilization of the chiral axis and multidomain defected films. The predictions of the integrated model are in qualitative agreement with experimental results and can potentially guide solution processing of other bio-related mesogenic solutions that seek to mimic the architecture of biological fibrous composites.

Orientation Relaxation Dynamics in Cellulose Nanocrystal Dispersions in the Chiral Liquid Crystalline Phase

“…Their results accurately mapped the same shear regions that have been observed in previous experimental results . A recent study by Rey et al used a slightly different LdG formulation to model CNC thin film formation . Their model coupled the local rod orientation to a time-dependent spatially varying concentration function to simulate drying effects.…”

Relaxation dynamics in bio-colloidal cholesteric liquid crystals confined to cylindrical geometry

“…During Phase (I), all fibers, which are in the para-nematic state, lose their initial order parameter, S i = 0.6 (ref. 42 ), and then turn into a low-order-parameter paranematic state (nearly isotropic), S d,BLG ≈ 0.33 ( Fig. 2 and Supplementary Movies 3 and 4).…”

“…During Phase (I), the order parameter of CNC fibers that are in the para-nematic medium is dramatically dropped to S d,CNC ≈ 0 at the beginning of relaxation despite their initial order parameter S i = 0.6 (ref. 42 ) and as a consequence, isotropic phase emerges from the para-nematic medium, followed by Phase (II), where the chiral front propagates into an isotropic medium (Supplementary Movie 5).…”

“…To capture this state, the governing equations are subjected to where S i , as mentioned earlier, stands for initial order parameter and equals to 0.6 (ref. 42 ). Readers are referred to Supplementary Note 13 for a detailed discussion on the numerical simulation methods.…”

“…The difficulty in the estimation of viscoelastic properties of BCLLCs stems from the fact that standard techniques for viscoelastic properties measurements are based on applying a magnetic or electrical field to reorient mesogenic constituents [35][36][37][38][39] and, in general, these techniques are not readily applicable for BCLLCs due to their low diamagnetic and dielectric susceptibilities 39,40 . In this case, the convenient alternative is flow alignment 1,[41][42][43] . To destabilize and unwind the chiral helices, rather than employing external fields such as magnetic or electric field, we thus rely on the surface tension-driven flow-induced orientation 25 created during capillary filling.…”