Bendable crystals tie current thinking in knots

August 29, 2017, University of Queensland
Bendable crystals tie current thinking in knots
Credit: University of Queensland

Queensland researchers have shown that single crystals, typically thought of as brittle and inelastic, are flexible enough to be bent repeatedly and even tied in a knot.

Researchers from Queensland University of Technology (QUT) and The University of Queensland (UQ) determined and measured the structural mechanism behind the elasticity of the crystals down to the atomic level.

Their work, published in Nature Chemistry, opens the door for the use of flexible crystals in applications in industry and technology. 

The research was led by ARC Future Fellows Associate Professor Jack Clegg in UQ's School of Chemistry and Molecular Biosciences and Associate Professor John McMurtrie in QUT's Science and Engineering Faculty. 

Associate Professor McMurtrie said the results challenged conventional thinking about crystalline structures.

"Crystals are something we work with a lot – they're typically grown in small blocks, are hard and brittle, and when struck or bent they crack or shatter," he said.

"While it has previously been observed that some crystals could bend, this is the first study to examine the process in detail.

"We found that the crystals exhibit traditional characteristics of not only hard matter, but soft matter like nylon."

The researchers grew bendable crystals about the width of a fishing line and up to five centimetres long from a common metal compound – copper (II) acetylacetonate. They mapped changes in the atomic scale structure when the crystals were bent using X-ray measurements performed at the Australian Synchrotron.

Crystals from six other structurally related compounds, some containing copper and some other metals, were also tested and found to be flexible.  

Associate Professor Clegg said the experiments showed that the crystals can be repeatedly bent and return quickly to their original shape with no signs of breaking or cracking when the force bending them is removed.

"Under strain the molecules in the crystal reversibly rotate and reorganise to allow the compression and expansion required for elasticity and still maintain the integrity of the crystal structure," he said.

"The ability of crystals to bend flexibly has wide-ranging implications in industry and technology.

"Crystallinity is a property that underpins a variety of existing technologies, including lasers and semi-conductors which are used in almost every electronic device, from DVD players to mobile phones and computers.

"But the hardness that makes them suitable for high-strength industrial components limits their use in other technologies. Flexible crystals like these could lead to new hybrid materials for numerous applications, from components of planes and spacecraft to parts of motion or pressure sensors and electronic devices."

Associate Professor McMurtrie said the method the researchers have developed to measure the changes during bending could also be used to explore flexibility in any other crystals.

"This is an exciting prospect given that there are millions of different types of already known and many more yet to be discovered," he said.

"Bending the crystal changes its optical and magnetic properties, and our next step is to explore these optical and magnetic responses with a view to identifying applications in new technologies."

Explore further: New strategy to design mechano-responsive luminescent materials

More information: Anna Worthy et al. Atomic resolution of structural changes in elastic crystals of copper(II) acetylacetonate, Nature Chemistry (2017). DOI: 10.1038/nchem.2848

Related Stories

Superior crystals grown from levitating droplets

December 6, 2016

Crystals that don't experience mechanical stress during growth have superior quality. Levitating liquid metal is the idea behind the project 'Perfecting metal crystals' led by the University of Twente in the Netherlands.

Microseeding: A new way to overcome hemihedral twinning?

December 15, 2016

Twinning is a crystal-growth disorder in which the specimen is composed of distinct domains whose orientations differ but are related in a particular, well-defined way. Twinning, which is a known problem in protein crystallography, ...

Research reveals inner workings of liquid crystals

March 20, 2017

Liquid crystals are used in everything from tiny digital watches to huge television screens, from optical devices to biomedical detectors. Yet little is known of their precise molecular structure when portions of such crystals ...

On the path toward molecular robots

March 10, 2017

Scientists in Japan have developed light-powered molecular motors that repetitively bend and unbend, bringing us closer to molecular robots.

Recommended for you

Scientists create diodes made of light

March 16, 2018

Photonics researchers at the National Physical Laboratory (NPL) have achieved the extra-ordinary by creating a diode consisting of light that can be used, for the first time, in miniaturised photonic circuits, as published ...

Quantum speed limits are not actually quantum

March 15, 2018

Quantum mechanics has fundamental speed limits—upper bounds on the rate at which quantum systems can evolve. However, two groups working independently have published papers showing for the first time that quantum speed ...

Thermally driven spin current in DNA

March 15, 2018

An emerging field that has generated a wide range of interest, spin caloritronics, is an offshoot of spintronics that explores how heat currents transport electron spin. Spin caloritronics researchers are particularly interested ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.