[Todos] Fwd: [Perintema] Seminario "Biological Plywoods: Lessons from Nature's Fibrous Composites"

[ersoule en fi.mdp.edu.ar]

COMPUTATIONAL ENGINEERING OF CHOLESTERIC COLLAGEN FILMS: RHEOLOGICAL 
PROPERTIES, HYDRODYNAMICS AND FILM FORMATION

Lugar y fecha: Aula Magna, martes 23 de mayo a las 11:00 hs

Disertante: ALEJANDRO REY
El profesor Alejandro Rey, originario de Argentina, es profesor en la 
Universidad McGill desde 1988, y director del Grupo de Investigación en 
Modelado de Materiales perteneciente al Departamento de ingeniería
Química de dicha universidad. Ha dictado cursos en nuestra institución 
como profesor visitante en dos ocasiones en el marco del subsidio 
Milstein del programa raíces, y actualmente se encuentra visitando 
nuestra institución por tercera vez en el marco el subsidio Milstein y 
del programa DOCTORAR.

Resumen:
This seminar presents recent theory and simulation1-4 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 , finely tuned dehydration is shown 
to lead to defect-free films when the time scale of chirality formation 
is in the proper ratio with the water removal rate. The integrated model 
can be applied to other cholesteric biomaterials such as 
nano-crystalline cellulose and silk solutions.

1. A.D. Rey, "Liquid Crystal Models of Biological Materials and 
Processes”, Soft Matter, 6-5, 3402-3429, 2010.
2. Echeverria, Coro, et al. "Two negative minima of the first normal 
stress difference in a cellulose‐based cholesteric liquid crystal: Helix 
uncoiling." Journal of Polymer Science Part B: Polymer Physics 55.10 
(2017): 821-830
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.O. F. Aguilar Gutiérrez and A.D. Rey, "Geometric Reconstruction of 
Biological Orthogonal Plywoods", Soft Matter, DOI: 10.1039/C5SM02214B, 
Nov 19, 2015, 12, pp 1184 - 1191, 2016.