Campuses:

Computational Engineering of Cholesteric Collagen Films: Rheological Properties, Hydrodynamics and Film Formation

Tuesday, January 16, 2018 - 11:30am - 12:20pm
Lind 305
Alejandro Rey (McGill University)
This lecture presents recent theory and simulation 1-4 of the formation of thin defect-free cholesteric collagen films by a non-equilibrium self-assembly process that involves dilution, flow-casting, and dehydration. To control and design defect-free films an integrated quantitative understanding of all the mechanisms that operate in the film formation are necessary. This work
uses a wide range of experimental information and measurements that include phase diagrams, shear rheology, film casting and drying to build a multi-transport computational model of the entire process. The goal is to first identify all the processing constraints and materials properties and then identify the processing envelope that avoids microstructural defects and leads to a perfect, chiral, collagen thin homogeneous film with a nano-wrinkled surface. Rheological data are used to find molecular aspect ratio, orientational diffusivity and flow-aligning functions. Four roll flow kinematics is then used to identify the required flow type and strength to align dilute collagen solutions and form films with suitable initial structures. Finally, the solution to a novel Model C coupling chiral phase ordering and dehydration in an evolving geometry shows how a finely tuned water mass transfer leads to defect-free films when the time scale of chirality formation is in the proper ratio with the water removal rate. Finally, surface nano-wrinkling of collagen surfaces is reproduced the liquid crystal shape equation. The integrated model can be applied to other cholesteric biomaterials such as nano-crystalline cellulose and silk solutions.

References
1. A.D. Rey, "Liquid Crystal Models of Biological Materials and Processes”, Soft Matter, 6-5, 3402-3429, 2010.

2. Gutierrez, Oscar F. Aguilar, and Alejandro D. Rey. "Biological plywood film formation from para-nematic liquid
crystalline organization." Soft matter 13.44 (2017): 8076-8088.

3.O. F. Aguilar Gutiérrez and A.D. Rey, "Theory and Simulation of Cholesteric Film Formation Flows of Dilute
Collagen Solutions", Langmuir, 10.1021/acs.langmuir.6b0344, 32 (45), pp 11799–11812, Oct 19, 2016.

4. Rofouie, Pardis, Damiano Pasini, and Alejandro D. Rey. "Nano-scale surface wrinkling in chiral liquid crystals
and plant-based plywoods." Soft Matter 11.6 (2015): 1127-1139.