Controlled fragmentation of multimaterial fibres and films via polymer cold-drawing.
Polymer cold-drawing is a process in which tensile stress reduces the diameter of a drawn fibre (or thickness of a drawn film) and orients the polymeric chains. Cold-drawing has long been used in industrial applications, including the production of flexible fibres with high tensile strength such as polyester and nylon. However, cold-drawing of a composite structure has been less studied. Here we show that in a multimaterial fibre composed of a brittle core embedded in a ductile polymer cladding, cold-drawing results in a surprising phenomenon: controllable and sequential fragmentation of the core to produce uniformly sized rods along metres of fibre, rather than the expected random or chaotic fragmentation. These embedded structures arise from mechanical-geometric instabilities associated with 'neck' propagation. Embedded, structured multimaterial threads with complex transverse geometry are thus fragmented into a periodic train of rods held stationary in the polymer cladding. These rods can then be easily extracted via selective dissolution of the cladding, or can self-heal by thermal restoration to re-form the brittle thread. Our method is also applicable to composites with flat rather than cylindrical geometries, in which case cold-drawing leads to the break-up of an embedded or coated brittle film into narrow parallel strips that are aligned normally to the drawing axis. A range of materials was explored to establish the universality of this effect, including silicon, germanium, gold, glasses, silk, polystyrene, biodegradable polymers and ice. We observe, and verify through nonlinear finite-element simulations, a linear relationship between the smallest transverse scale and the longitudinal break-up period. These results may lead to the development of dynamical and thermoreversible camouflaging via a nanoscale Venetian-blind effect, and the fabrication of large-area structured surfaces that facilitate high-sensitivity bio-detection.
CREOL, The College of Optics &Photonics, University of Central Florida, Orlando, Florida 32816, USA.
Soroush
S
Shabahang
CREOL, The College of Optics &Photonics, University of Central Florida, Orlando, Florida 32816, USA.
Guangming
G
Tao
CREOL, The College of Optics &Photonics, University of Central Florida, Orlando, Florida 32816, USA.
Joshua J
JJ
Kaufman
Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Yangyang
Y
Qiao
School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore.
Lei
L
Wei
Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Thomas
T
Bouchenot
Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Ali P
AP
Gordon
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Yoel
Y
Fink
Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Yuanli
Y
Bai
Department of Physics, University of South Florida, Tampa, Florida 33620, USA.
Robert S
RS
Hoy
CREOL, The College of Optics &Photonics, University of Central Florida, Orlando, Florida 32816, USA.|Department of Materials Science and Engineering, University of Central Florida, Orlando, Florida 32816, USA.
Ayman F
AF
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