title: A bio-inspired microstructure induced by slow injection moulding of cylindrical block copolymers.
abstract: It is well known that block copolymers with cylindrical morphology show alignment with shear, resulting in anisotropic mechanical properties. Here we show that well-ordered bi-directional orientation can be achieved in such materials by slow injection moulding. This results in a microstructure, and anisotropic mechanical properties, similar to many natural tissues, making this method attractive for engineering prosthetic fibrous tissues. An application of particular interest to us is prosthetic polymeric heart valve leaflets, mimicking the shape, microstructure and hence performance of the native valve. Anisotropic layers have been observed for cylinder-forming block copolymers centrally injected into thin circular discs. The skin layers exhibit orientation parallel to the flow direction, whilst the core layer shows perpendicularly oriented domains; the balance of skin to core layers can be controlled by processing parameters such as temperature and injection rate. Heart valve leaflets with a similar layered structure have been prepared by injection moulding. Numerical modelling demonstrates that such complex orientation can be explained and predicted by the balance of shear and extensional flow.
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge, CB2 3RA, UK. gdm14@cam.ac.uk.
authors.forename: Joanna
authors.initials: J
authors.lastname: Stasiak
authors.forename: Jacob
authors.initials: J
authors.lastname: Brubert
authors.forename: Marta
authors.initials: M
authors.lastname: Serrani
authors.forename: Sukumaran
authors.initials: S
authors.lastname: Nair
authors.forename: Francesco
authors.initials: F
authors.lastname: de Gaetano
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Costantino
authors.forename: Geoff D
authors.initials: GD
authors.lastname: Moggridge
mesh_terms: D000818:Animals; D016880:Anisotropy; D001021:Aortic Valve; D011108:Polymers / Q000737:chemistry*; D053838:Scattering, Small Angle; D013552:Swine; D023822:Tissue Engineering; D014961:X-Ray Diffraction
chemical_list: D011108:Polymers