Improved Manmade spider silk

A team of architects and chemists from the University of Cambridge has designed super-stretchy and strong fibers which are almost entirely composed of water, and could be used to make textiles, sensors and other materials. The fibers, which resemble miniature bungee cords as they can absorb large amounts of energy, are sustainable, non-toxic and can be made at room temperature.

This new method not only improves upon earlier methods of making synthetic spider silk, since it does not require high energy procedures or extensive use of harmful solvents, but it could substantially improve methods of making synthetic fibers of all kinds, since other types of synthetic fibers also rely on high-energy, toxic methods.

"Although our fibers are not as strong as the strongest spider silks, they can support stresses in the range of 100 to 150 megapascals, which is similar to other synthetic and natural silks," said Shah. "However, our fibers are non-toxic and far less energy-intensive to make."

The fibers are capable of self-assembly at room temperature, and are held together by supramolecular host-guest chemistry, which relies on forces other than covalent bonds, where atoms share electrons.

The fibers also show very high damping capacity, meaning that they can absorb large amounts of energy, similar to a bungee cord. There are very few synthetic fibers which have this capacity, but high damping is one of the special characteristics of spider silk. The researchers found that the damping capacity in some cases even exceeded that of natural silks.

PNAS - Bioinspired supramolecular fibers drawn from a multiphase self-assembled hydrogel

"Currently they make around a few tens of milligrams of these materials and then pull fibers from them," he says. "But we want to try and do this at a much larger scale."

To do so, the team is working on a robotic device to pull and spin fibers more quickly and at a larger scale than previously. They've had some success, Shah says, and continue to explore the process.

Significance

Fiber materials have great impact on our daily lives, with their use ranging from textiles to functional reinforcements in composites. Although the manufacturing process of manmade fibers is potentially limited by extensive energy consumption, spiders can readily spin silk fibers at room temperature. Here, we report a class of material that is based on a self-assembled hydrogel constructed with dynamic host-guest cross-links between functional polymers. Supramolecular fibers can be drawn from this hydrogel at room temperature. The supramolecular fiber exhibits better tensile and damping properties than conventional regenerated fibers, such as viscose, artificial silks, and hair. Our approach offers a sustainable alternative to current fiber manufacturing strategies.

Abstract

Inspired by biological systems, we report a supramolecular polymer-colloidal hydrogel (SPCH) composed of 98 wt % water that can be readily drawn into uniform (6 micron thick) "supramolecular fibers" at room temperature. Functionalized polymer-grafted silica nanoparticles, a semicrystalline hydroxyethyl cellulose derivative, and cucurbit uril undergo aqueous self-assembly at multiple length scales to form the SPCH facilitated by host-guest interactions at the molecular level and nanofibril formation at colloidal-length scale. The fibers exhibit a unique combination of stiffness and high damping capacity (60-70%), the latter exceeding that of even biological silks and cellulose-based viscose rayon. The remarkable damping performance of the hierarchically structured fibers is proposed to arise from the complex combination and interactions of "hard" and "soft" phases within the SPCH and its constituents. SPCH represents a class of hybrid supramolecular composites, opening a window into fiber technology through low-energy manufacturing.