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

When stretched or deformed, shape memory polymers return to their first styles immediately after heat or gentle is utilized. These elements present excellent guarantee for soft robotics, intelligent biomedical equipment and deployable space buildings, but until now they haven’t been equipped to shop enough energy.

Now, researchers reporting in ACS Central Science have formulated a shape memory polymer that stores nearly six occasions extra energy than former variations.

An artificial muscle mass created of a stretched shape memory polymer contracts upon heating, bending a mannequin’s arm. Picture credit score: Adapted from ACS Central Science 2021, DOI: 10.1021/acscentsci.1c00829

Shape memory polymers alternate between an first, undeformed condition and a secondary, deformed condition. The deformed condition is developed by stretching the polymer and is held in spot by molecular improvements, these as dynamic bonding networks or pressure-induced crystallization, that are reversed with heat or gentle. The polymer then returns to its first condition by the release of stored entropic energy. But it’s been challenging for experts to make these polymers conduct energy-intensive responsibilities. Zhenan Bao and colleagues wanted to build a new style of shape memory polymer that stretches into a steady, very elongated condition, allowing for it to release big amounts of energy when returning to its first condition.

The researchers integrated 4-,4’-methylene bisphenylurea units into a poly(propylene glycol) polymer backbone. In the polymer’s first condition, polymer chains ended up tangled and disordered. Stretching caused the chains to align and sort hydrogen bonds between urea teams, creating supermolecular buildings that stabilized the very elongated condition. Heating caused the bonds to break and the polymer to deal to its preliminary, disordered condition.

In exams, the polymer could be stretched up to five occasions its first length and shop up to seventeen.9 J/g energy –– nearly six occasions extra energy than former shape memory polymers. The workforce demonstrated that the stretched substance could use this energy to lift objects 5,000 occasions its have body weight upon heating. They also created an artificial muscle mass by attaching the pre-stretched polymer to the upper and reduce arm of a picket mannequin. When heated, the substance contracted, causing the mannequin to bend its arm at the elbow. In addition to its file-large energy density, the shape memory polymer is also economical (raw elements price tag about $eleven for every lb) and effortless to make, the researchers say.

Supply: acs.org