On the heels of my May 29, 2015 post about synthesized spider silk at the Massachusetts Institute of Technology (MIT), researchers at the École Polytechnique de Montréal (Polytechnique Montreal) have also synthesized spider silk according to a June 3, 2015 news item on Nanowerk (Note: A link has been removed),
Professors Frederick Gosselin and Daniel Therriault, along with their master’s student Renaud Passieux, are not related to Spiderman. Nevertheless, these Polytechnique Montreal researchers have produced an ultra-tough polymer fibre directly inspired by spider silk! They recently published an article about the project in the journal Advanced Materials (“Instability-Assisted Direct Writing of Microstructured Fibers Featuring Sacrificial Bonds”).
A June 3, 2015 École Polytechnique de Montréal news release (also on EurekAlert), which originated the news item, further describes the achievement (at the microscale rather than the nanoscale),
Three to eight microns in diameter but five to ten times tougher than steel or Kevlar: despite its lightness, spider silk has such remarkable elongation and stretch-resistance properties that humans have long sought to replicate it, in order to make products with those same characteristics.
In large part, spider silk owes its exceptional strength – meaning its ability to absorb a large amount of energy before failing – to the particular molecular structure of the protein chain of which it’s composed. The mechanical origin of its strength drew the interest of researchers at the Laboratory for Multiscale Mechanics in Polytechnique Montréal’s Department of Mechanical Engineering.
“The silk protein coils upon itself like a spring. Each loop of the spring is attached to its neighbours with sacrificial bonds, chemical connections that break before the main molecular structural chain tears,” explained Professor Gosselin, who, along with his colleague Daniel Therriault, is co-supervising Renaud Passieux’s master’s research work. He added: “To break the protein by stretching it, you need to uncoil the spring and break each of the sacrificial bonds one by one, which takes a lot of energy. This is the mechanism we’re seeking to reproduce in laboratory,”
Imitating nature with polymer fibres
Their project involves making micrometric-sized microstructured fibres that have mechanical properties similar to those of spider silk. “It consists in pouring a filament of viscous polymeric solution toward a sub-layer that moves at a certain speed. So we create an instability,” said Renaud Passieux. “The filament forms a series of loops or coils, kind of like when you pour a thread of honey onto a piece of toast. [emphasis mine] Depending on the instability determined by the way the fluid runs, the fibre presents a particular geometry. It forms regular periodic patterns, which we call instability patterns.”
The fibre then solidifies as the solvent evaporates. Some instability patterns feature the formation of sacrificial bonds when the filament makes a loop and bonds to itself. At that point, it takes a pull with a strong energy output on the resulting fibre to succeed in breaking the sacrificial bonds, as they behave like protein-based spider silk.
“This project aims to understand how the instability used in making the substance influences the loops’ geometry and, as a result, the mechanical properties of the fibres we obtain,” explained Professor Therriault. “Our challenge is that the manufacturing process is multiphysical. It draws on concepts from numerous fields: fluid mechanics, microfabrication, strength of materials, polymer rheology and more.”
A vast range of applications for future tough fibre composites
These researchers think that one day, there will certainly be composites obtained by weaving together tough fibres of the type they’re currently developing. Such composites could, for example, make it possible to manufacture new safer and lighter casings for aircraft engines, which would prevent debris from dispersing in case of explosion. Many other applications can be foreseen, from surgical devices to bulletproof clothing to vehicle parts.
Here’s a link to and a citation for the paper,
Instability-Assisted Direct Writing of Microstructured Fibers Featuring Sacrificial Bonds by Renaud Passieux, Leigh Guthrie, Somayeh Hosseini Rad, Martin Lévesque, Daniel Therriault, & Frédérick P. Gosselin. Advanced Materials DOI: 10.1002/adma.201500603 First published: 15 May 2015
This paper is behind a paywall.
The researchers have also produced a video illustrating the ‘honey’ analogy as it relates to their work with spider silk,