High-energy shape memory polymer could someday help robots flex their muscles

Nancy J. Delong

When stretched or deformed, condition memory polymers return to their original styles right after warmth or gentle is used. These materials display terrific promise for gentle robotics, clever biomedical devices and deployable space structures, but right up until now they haven’t been equipped to retail outlet adequate strength.

Now, scientists reporting in ACS Central Science have formulated a condition memory polymer that retailers virtually 6 situations a lot more strength than prior versions.

An synthetic muscle designed of a stretched condition memory polymer contracts on heating, bending a mannequin’s arm. Impression credit rating: Adapted from ACS Central Science 2021, DOI: ten.1021/acscentsci.1c00829

Shape memory polymers alternate involving an original, undeformed point out and a secondary, deformed point out. The deformed point out is created by stretching the polymer and is held in location by molecular variations, these as dynamic bonding networks or pressure-induced crystallization, that are reversed with warmth or gentle. The polymer then returns to its original point out by the release of stored entropic strength. But it’s been challenging for experts to make these polymers conduct strength-intensive duties. Zhenan Bao and colleagues wanted to create a new sort of condition memory polymer that stretches into a secure, highly elongated point out, enabling it to release big amounts of strength when returning to its original point out.

The scientists included four-,4’-methylene bisphenylurea models into a poly(propylene glycol) polymer spine. In the polymer’s original point out, polymer chains have been tangled and disordered. Stretching prompted the chains to align and sort hydrogen bonds involving urea groups, producing supermolecular structures that stabilized the highly elongated point out. Heating prompted the bonds to break and the polymer to deal to its original, disordered point out.

In checks, the polymer could be stretched up to five situations its original size and retail outlet up to seventeen.9 J/g strength –– virtually 6 situations a lot more strength than prior condition memory polymers. The group shown that the stretched material could use this strength to raise objects 5,000 situations its possess pounds on heating. They also designed an synthetic muscle by attaching the pre-stretched polymer to the upper and reduced arm of a wooden model. When heated, the material contracted, resulting in the model to bend its arm at the elbow. In addition to its report-large strength density, the condition memory polymer is also low-cost (raw materials price about $eleven for each lb) and simple to make, the scientists say.

Source: acs.org

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